Commonwealth Edison 10-Q3 Nov 212021 Q3 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page	9 Months Ended
Cover Page	Sep. 30, 2021shares
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-16169
Entity Registrant Name	EXELON CORPORATION
Entity Tax Identification Number	23-2990190
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	10 South Dearborn Street
Entity Address, Address Line Two	P.O. Box 805379
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60680-5379
City Area Code	(800)
Local Phone Number	483-3220
Title of 12(b) Security	Common stock, without par value
Trading Symbol	EXC
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock Shares Outstanding	978,317,787
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001109357
Amendment Flag	false
Exelon Generation Co L L C [Member]
Entity File Number	333-85496
Entity Registrant Name	EXELON GENERATION COMPANY, LLC
Entity Tax Identification Number	23-3064219
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	300 Exelon Way
Entity Address, City or Town	Kennett Square
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19348-2473
City Area Code	(610)
Local Phone Number	765-5959
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001168165
Commonwealth Edison Co [Member]
Entity File Number	001-01839
Entity Registrant Name	COMMONWEALTH EDISON COMPANY
Entity Tax Identification Number	36-0938600
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	10 South Dearborn Street
Entity Address, Address Line Two	49th Floor
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60603-2300
City Area Code	(312)
Local Phone Number	394-4321
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	127,021,383
Entity Central Index Key	0000022606
PECO Energy Co [Member]
Entity File Number	000-16844
Entity Registrant Name	PECO ENERGY COMPANY
Entity Tax Identification Number	23-0970240
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	P.O. Box 8699
Entity Address, Address Line Two	2301 Market Street
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19101-8699
City Area Code	(215)
Local Phone Number	841-4000
Title of 12(b) Security	Cumulative Preferred Security, Series D
Trading Symbol	EXC/28
Security Exchange Name	NYSE
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	170,478,507
Entity Central Index Key	0000078100
Baltimore Gas and Electric Company [Member]
Entity File Number	001-01910
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC COMPANY
Entity Tax Identification Number	52-0280210
Entity Incorporation, State or Country Code	MD
Entity Address, Address Line One	2 Center Plaza
Entity Address, Address Line Two	110 West Fayette Street
Entity Address, City or Town	Baltimore
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21201-3708
City Area Code	(410)
Local Phone Number	234-5000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	1,000
Entity Central Index Key	0000009466
Pepco Holdings LLC [Member]
Entity File Number	001-31403
Entity Registrant Name	PEPCO HOLDINGS LLC
Entity Tax Identification Number	52-2297449
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068-0001
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001135971
Potomac Electric Power Company [Member]
Entity File Number	001-01072
Entity Registrant Name	POTOMAC ELECTRIC POWER COMPANY
Entity Tax Identification Number	53-0127880
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068-0001
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	100
Entity Central Index Key	0000079732
Delmarva Power and Light Company [Member]
Entity File Number	001-01405
Entity Registrant Name	DELMARVA POWER & LIGHT COMPANY
Entity Tax Identification Number	51-0084283
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702-5440
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	1,000
Entity Central Index Key	0000027879
Atlantic City Electric Company [Member]
Entity File Number	001-03559
Entity Registrant Name	ATLANTIC CITY ELECTRIC COMPANY
Entity Tax Identification Number	21-0398280
Entity Incorporation, State or Country Code	NJ
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702-5440
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	8,546,017
Entity Central Index Key	0000008192
DISTRICT OF COLUMBIA \| Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	DC
VIRGINIA \| Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	VA
VIRGINIA \| Delmarva Power and Light Company [Member]
Entity Incorporation, State or Country Code	VA
DELAWARE \| Delmarva Power and Light Company [Member]
Entity Incorporation, State or Country Code	DE

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating revenues
Revenues from alternative revenue programs		$ (47)	$ (11)	$ 129	$ (66)
Operating revenues from affiliates		0	1	0	4
Total operating revenues		8,910	8,853	26,715	24,925
Operating expenses
Operating and maintenance		1,992	2,732	6,416	7,370
Depreciation and amortization		1,624	1,289	4,988	3,312
Taxes other than income taxes		468	452	1,337	1,299
Total operating expenses		7,117	8,087	24,758	22,387
Gain on sales of assets and businesses		65	3	147	16
Operating income (loss)		1,858	769	2,104	2,554
Other income and (deductions)
Interest expense, net		(391)	(398)	(1,161)	(1,222)
Interest expense to affiliates		(6)	(6)	(19)	(19)
Other, net		(55)	421	751	352
Total other income and (deductions)		(452)	17	(429)	(889)
Income before income taxes		1,406	786	1,675	1,665
Income taxes		174	216	229	141
Equity in losses of unconsolidated affiliates		(3)	(1)	(5)	(5)
Net income (loss)		1,229	569	1,441	1,519
Net income (loss) attributable to noncontrolling interests		26	68	126	(85)
Net Income (Loss) Available to Common Stockholders, Basic		1,203	501	1,315	1,604
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(1)	(10)	(4)	(30)
Actuarial loss reclassified to periodic benefit cost		56	49	167	142
Pension and non-pension postretirement benefit plan valuation adjustment		14	(13)	15	(17)
Unrealized (loss) gain on cash flow hedges		0	(1)	(1)	(2)
Unrealized gain (loss) on foreign currency translation		(3)	3	0	(3)
Other comprehensive income		66	28	177	90
Comprehensive income		1,295	597	1,618	1,609
Comprehensive income (loss) attributable to noncontrolling interests		26	68	126	(85)
Comprehensive income attributable to common shareholders/membership interest		$ 1,269	$ 529	$ 1,492	$ 1,694
Average shares of common stock outstanding:
Basic average shares of common stock outstanding		979	976	978	976
Assumed exercise and/or distributions of stock-based awards		1	1	1	0
Diluted average shares of common stock outstanding	[1]	980	977	979	976
Earnings per average common share
Basic earnings per average common share		$ 1.23	$ 0.51	$ 1.34	$ 1.64
Diluted earnings per average common share		$ 1.23	$ 0.51	$ 1.34	$ 1.64
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	1	0	1
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		$ 324	$ 331	$ 872	$ 932
Total operating revenues		4,406	4,659	14,117	13,272
Operating expenses
Purchased power and fuel from affiliates		4	3	0	(6)
Operating and maintenance		761	1,605	2,955	3,779
Operating and maintenance from affiliates		177	132	458	409
Depreciation and amortization		866	558	2,735	1,161
Taxes other than income taxes		115	118	354	364
Total operating expenses		3,465	4,727	14,605	12,674
Gain on sales of assets and businesses		65	0	144	12
Operating income (loss)		1,006	(68)	(344)	610
Other income and (deductions)
Interest expense, net		(73)	(72)	(214)	(251)
Interest expense to affiliates		(4)	(8)	(11)	(26)
Other, net		(115)	367	561	199
Total other income and (deductions)		(192)	287	336	(78)
Income before income taxes		814	219	(8)	532
Income taxes		177	100	108	41
Equity in losses of unconsolidated affiliates		(4)	(2)	(6)	(6)
Net income (loss)		633	117	(122)	485
Net income (loss) attributable to noncontrolling interests		26	68	125	(85)
Net income attributable to membership interest		607	49	(247)	570
Other comprehensive income (loss), net of income taxes
Unrealized (loss) gain on cash flow hedges		0	0	(1)	(1)
Unrealized gain (loss) on foreign currency translation		(4)	3	0	(3)
Other comprehensive income		(4)	3	(1)	(4)
Comprehensive income		629	120	(123)	481
Comprehensive income (loss) attributable to noncontrolling interests		26	68	125	(85)
Comprehensive income attributable to common shareholders/membership interest		603	52	(248)	566
Commonwealth Edison Co [Member]
Operating revenues
Revenues from alternative revenue programs		(32)	(38)	32	(51)
Operating revenues from affiliates		9	15	19	31
Total operating revenues		1,789	1,643	4,840	4,499
Operating expenses
Purchased power and/or fuel from affiliates		93	71	256	252
Operating and maintenance		257	252	752	964
Operating and maintenance from affiliates		73	69	217	209
Depreciation and amortization		304	294	893	841
Taxes other than income taxes		91	81	243	227
Total operating expenses		1,428	1,302	3,833	3,798
Operating income (loss)		361	341	1,007	701
Other income and (deductions)
Interest expense, net		(95)	(92)	(282)	(277)
Interest expense to affiliates		(3)	(3)	(10)	(10)
Other, net		13	10	35	32
Total other income and (deductions)		(85)	(85)	(257)	(255)
Income before income taxes		276	256	750	446
Income taxes		56	60	141	142
Net income (loss)		220	196	609	304
Other comprehensive income (loss), net of income taxes
Comprehensive income		220	196	609	304
PECO Energy Co [Member]
Operating revenues
Revenues from alternative revenue programs		3	5	20	10
Operating revenues from affiliates		2	3	6	7
Total operating revenues		818	813	2,399	2,306
Operating expenses
Purchased power and/or fuel from affiliates		60	67	141	144
Operating and maintenance		220	214	580	628
Operating and maintenance from affiliates		43	37	126	114
Depreciation and amortization		86	85	259	259
Taxes other than income taxes		51	53	143	131
Total operating expenses		677	658	1,908	1,900
Operating income (loss)		141	155	491	406
Other income and (deductions)
Interest expense, net		(37)	(36)	(110)	(100)
Interest expense to affiliates		(3)	(3)	(9)	(8)
Other, net		7	6	20	12
Total other income and (deductions)		(33)	(33)	(99)	(96)
Income before income taxes		108	122	392	310
Income taxes		(3)	(16)	9	(7)
Net income (loss)		111	138	383	317
Other comprehensive income (loss), net of income taxes
Comprehensive income		111	138	383	317
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		(24)	(9)	(17)	(10)
Operating revenues from affiliates		7	6	20	16
Total operating revenues		770	731	2,426	2,284
Operating expenses
Purchased power and/or fuel from affiliates		64	83	193	249
Operating and maintenance		159	152	458	445
Operating and maintenance from affiliates		46	39	137	122
Depreciation and amortization		142	133	434	405
Taxes other than income taxes		72	68	211	200
Total operating expenses		709	642	2,080	1,903
Operating income (loss)		61	89	346	381
Other income and (deductions)
Interest expense, net		(36)	(34)	(103)	(99)
Other, net		7	6	23	17
Total other income and (deductions)		(29)	(28)	(80)	(82)
Income before income taxes		32	61	266	299
Income taxes		(4)	8	(24)	26
Net income (loss)		36	53	290	273
Other comprehensive income (loss), net of income taxes
Comprehensive income		36	53	290	273
Pepco Holdings LLC [Member]
Operating revenues
Revenues from alternative revenue programs		6	31	94	(15)
Operating revenues from affiliates		3	6	10	13
Total operating revenues		1,470	1,368	3,854	3,554
Operating expenses
Purchased power and/or fuel from affiliates		100	106	277	288
Operating and maintenance		235	237	668	702
Operating and maintenance from affiliates		43	38	122	111
Depreciation and amortization		210	200	614	585
Taxes other than income taxes		127	121	349	343
Total operating expenses		1,155	1,102	3,167	3,057
Gain on sales of assets and businesses		0	0	0	2
Operating income (loss)		315	266	687	499
Other income and (deductions)
Interest expense, net		(67)	(67)	(201)	(201)
Other, net		16	16	52	42
Total other income and (deductions)		(51)	(51)	(149)	(159)
Income before income taxes		264	215	538	340
Income taxes		(2)	(1)	3	(77)
Equity in losses of unconsolidated affiliates		0	0	0	1
Net income (loss)		266	216	535	418
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		266	216	535	418
Potomac Electric Power Company [Member]
Operating revenues
Revenues from alternative revenue programs		9	18	54	20
Operating revenues from affiliates		2	3	4	6
Total operating revenues		660	611	1,736	1,650
Operating expenses
Purchased power and/or fuel from affiliates		69	80	200	219
Operating and maintenance		68	57	186	184
Operating and maintenance from affiliates		52	49	155	152
Depreciation and amortization		104	96	302	282
Taxes other than income taxes		105	100	282	279
Total operating expenses		501	465	1,396	1,364
Operating income (loss)		159	146	340	286
Other income and (deductions)
Interest expense, net		(35)	(35)	(104)	(103)
Other, net		12	10	37	28
Total other income and (deductions)		(23)	(25)	(67)	(75)
Income before income taxes		136	121	273	211
Income taxes		6	3	9	(16)
Net income (loss)		130	118	264	227
Other comprehensive income (loss), net of income taxes
Comprehensive income		130	118	264	227
Delmarva Power and Light Company [Member]
Operating revenues
Revenues from alternative revenue programs		(2)	8	17	(15)
Operating revenues from affiliates		2	3	6	7
Total operating revenues		360	337	1,040	954
Operating expenses
Purchased power and/or fuel from affiliates		26	21	63	60
Operating and maintenance		47	64	132	160
Operating and maintenance from affiliates		40	37	117	112
Depreciation and amortization		53	48	157	143
Taxes other than income taxes		17	16	50	49
Total operating expenses		295	296	858	843
Operating income (loss)		65	41	182	111
Other income and (deductions)
Interest expense, net		(15)	(15)	(47)	(47)
Other, net		3	2	9	7
Total other income and (deductions)		(12)	(13)	(38)	(40)
Income before income taxes		53	28	144	71
Income taxes		3	1	9	(20)
Net income (loss)		50	27	135	91
Other comprehensive income (loss), net of income taxes
Comprehensive income		50	27	135	91
Atlantic City Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		0	5	23	(20)
Operating revenues from affiliates		1	1	2	3
Total operating revenues		451	420	1,080	952
Operating expenses
Purchased power and/or fuel from affiliates		5	4	14	9
Operating and maintenance		46	45	128	140
Operating and maintenance from affiliates		35	32	103	98
Depreciation and amortization		46	48	133	134
Taxes other than income taxes		2	2	6	6
Total operating expenses		359	338	911	847
Gain on sales of assets and businesses		0	0	0	2
Operating income (loss)		92	82	169	107
Other income and (deductions)
Interest expense, net		(14)	(15)	(43)	(45)
Other, net		1	1	3	5
Total other income and (deductions)		(13)	(14)	(40)	(40)
Income before income taxes		79	68	129	67
Income taxes		(11)	(7)	(12)	(39)
Net income (loss)		90	75	141	106
Other comprehensive income (loss), net of income taxes
Comprehensive income		90	75	141	106
Generation commodities and services [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,084	4,331	13,250	12,348
Operating expenses
Purchased power and/or fuel		1,541	2,311	8,103	6,967
Generation commodities and services [Member] \| Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,082	4,328	13,245	12,340
Operating expenses
Purchased power and/or fuel		1,542	2,311	8,103	6,967
Rate-regulated utility revenues [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,873	4,533	13,336	12,643
Operating expenses
Purchased power and/or fuel		1,492	1,303	3,914	3,439
Electricity, US Regulated [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,657	4,365	12,432	11,585
Electricity, US Regulated [Member] \| Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,812	1,666	4,789	4,519
Operating expenses
Purchased power and/or fuel		610	535	1,472	1,305
Electricity, US Regulated [Member] \| PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		757	751	2,008	1,931
Operating expenses
Purchased power and/or fuel		206	190	540	495
Electricity, US Regulated [Member] \| Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		694	649	1,874	1,775
Operating expenses
Purchased power and/or fuel		206	155	501	376
Electricity, US Regulated [Member] \| Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,438	1,308	3,632	3,440
Operating expenses
Purchased power and/or fuel		431	393	1,087	979
Electricity, US Regulated [Member] \| Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		649	590	1,678	1,624
Operating expenses
Purchased power and/or fuel		103	83	271	248
Electricity, US Regulated [Member] \| Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		337	303	899	846
Operating expenses
Purchased power and/or fuel		103	103	289	270
Electricity, US Regulated [Member] \| Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		450	414	1,055	969
Operating expenses
Purchased power and/or fuel		225	207	527	460
Natural Gas, US Regulated [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		169	159	1,035	990
Natural Gas, US Regulated [Member] \| PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		56	54	365	358
Operating expenses
Purchased power and/or fuel		11	12	119	129
Natural Gas, US Regulated [Member] \| Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		93	85	549	503
Operating expenses
Purchased power and/or fuel		20	12	146	106
Natural Gas, US Regulated [Member] \| Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		23	23	118	116
Operating expenses
Purchased power and/or fuel		9	7	50	49
Natural Gas, US Regulated [Member] \| Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		23	23	118	116
Operating expenses
Purchased power and/or fuel		$ 9	$ 7	$ 50	$ 49

[1]	The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was zero for the three and nine months ended September 30, 2021 and approximately 1 million for the three and nine months ended September 30, 2020, respectively.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net income (loss)	$ 1,441	$ 1,519
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	6,204	4,419
Asset impairments	541	567
Gain on sales of assets and businesses	(147)	(16)
Deferred income taxes and amortization of investment tax credits	(45)	164
Net fair value changes related to derivatives	(1,244)	(448)
Net realized and unrealized (gains) losses on NDT funds	(383)	(59)
Unrealized loss on equity investments	83	0
Other non-cash operating activities	(293)	988
Changes in assets and liabilities:
Accounts receivable	(254)	1,195
Inventories	(101)	(67)
Accounts payable and accrued expenses	354	(519)
Option premiums paid, net	(186)	(131)
Collateral received (posted), net	2,111	644
Income taxes	250	(31)
Pension and non-pension postretirement benefit contributions	(602)	(580)
Other assets and liabilities	(3,588)	(3,423)
Net cash flows provided by operating activities	4,141	4,222
Cash flows from investing activities
Capital expenditures	(5,970)	(5,606)
Proceeds from NDT fund sales	5,766	3,370
Investment in NDT funds	(5,900)	(3,438)
Collection of deferred purchase price	3,052	2,518
Proceeds from sales of assets and businesses	801	46
Other investing activities	40	(2)
Net cash flows provided by (used in) investing activities	(2,211)	(3,112)
Cash flows from financing activities
Changes in short-term borrowings	(744)	(689)
Proceeds from short-term borrowings with maturities greater than 90 days	1,380	500
Issuance of long-term debt	3,406	6,756
Retirement of long-term debt	(1,618)	(5,158)
Dividends paid on common stock	(1,121)	(1,119)
Acquisition of CENG noncontrolling interest	(885)	0
Proceeds from employee stock plans	63	62
Other financing activities	(93)	(104)
Net cash flows provided by (used in) financing activities	388	248
Increase (decrease) in cash, restricted cash, and cash equivalents	2,318	1,358
Cash, restricted cash, and cash equivalents at beginning of period	1,166	1,122
Cash, restricted cash, and cash equivalents at end of period	3,484	2,480
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(334)	(11)
Increase in deferred purchase price	2,933	3,275
Increase in PPE related to ARO update	574	775
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(122)	485
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	3,951	2,266
Asset impairments	537	552
Gain on sales of assets and businesses	(144)	(12)
Deferred income taxes and amortization of investment tax credits	(204)	(51)
Net fair value changes related to derivatives	(1,244)	(448)
Net realized and unrealized (gains) losses on NDT funds	(383)	(59)
Unrealized loss on equity investments	83	0
Other non-cash operating activities	(582)	293
Changes in assets and liabilities:
Accounts receivable	(207)	1,463
Change in Receivables From Payables To Affiliates, Net	82	75
Inventories	(29)	(65)
Accounts payable and accrued expenses	357	(619)
Option premiums paid, net	(186)	(131)
Collateral received (posted), net	1,974	640
Income taxes	177	112
Pension and non-pension postretirement benefit contributions	(237)	(249)
Other assets and liabilities	(2,849)	(2,889)
Net cash flows provided by operating activities	974	1,363
Cash flows from investing activities
Capital expenditures	(1,086)	(1,212)
Proceeds from NDT fund sales	5,766	3,370
Investment in NDT funds	(5,900)	(3,438)
Collection of deferred purchase price	3,052	2,518
Proceeds from sales of assets and businesses	802	46
Other investing activities	5	5
Net cash flows provided by (used in) investing activities	2,639	1,289
Cash flows from financing activities
Changes in short-term borrowings	(340)	(280)
Proceeds from short-term borrowings with maturities greater than 90 days	880	500
Issuance of long-term debt	152	2,405
Retirement of long-term debt	(89)	(3,613)
Changes in Exelon/PHI intercompany money pool	(285)	0
Acquisition of CENG noncontrolling interest	(885)	0
Distributions to member	(1,373)	(1,406)
Contributions from member	64	64
Other financing activities	(45)	(48)
Net cash flows provided by (used in) financing activities	(1,921)	(2,378)
Increase (decrease) in cash, restricted cash, and cash equivalents	1,692	274
Cash, restricted cash, and cash equivalents at beginning of period	327	449
Cash, restricted cash, and cash equivalents at end of period	2,019	723
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(77)	(77)
Increase in deferred purchase price	2,933	3,275
Increase in PPE related to ARO update	550	775
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	609	304
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	893	841
Asset impairments	0	15
Deferred income taxes and amortization of investment tax credits	211	205
Other non-cash operating activities	95	354
Changes in assets and liabilities:
Accounts receivable	(72)	(104)
Change in Receivables From Payables To Affiliates, Net	(16)	(13)
Inventories	(6)	(2)
Accounts payable and accrued expenses	(36)	21
Collateral received (posted), net	68	3
Income taxes	(9)	(22)
Pension and non-pension postretirement benefit contributions	(176)	(145)
Other assets and liabilities	(376)	(380)
Net cash flows provided by operating activities	1,185	1,077
Cash flows from investing activities
Capital expenditures	(1,723)	(1,583)
Other investing activities	20	0
Net cash flows provided by (used in) investing activities	(1,703)	(1,583)
Cash flows from financing activities
Changes in short-term borrowings	(323)	11
Issuance of long-term debt	1,150	1,000
Retirement of long-term debt	(350)	(500)
Dividends paid on common stock	(380)	(374)
Contributions from parent	593	488
Other financing activities	(16)	(14)
Net cash flows provided by (used in) financing activities	674	611
Increase (decrease) in cash, restricted cash, and cash equivalents	156	105
Cash, restricted cash, and cash equivalents at beginning of period	405	403
Cash, restricted cash, and cash equivalents at end of period	561	508
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(118)	49
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	383	317
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	259	259
Deferred income taxes and amortization of investment tax credits	19	(5)
Other non-cash operating activities	4	27
Changes in assets and liabilities:
Accounts receivable	47	(2)
Change in Receivables From Payables To Affiliates, Net	16	(7)
Inventories	(21)	(3)
Accounts payable and accrued expenses	(23)	32
Income taxes	55	48
Pension and non-pension postretirement benefit contributions	(15)	(18)
Other assets and liabilities	(87)	(13)
Net cash flows provided by operating activities	637	635
Cash flows from investing activities
Capital expenditures	(878)	(824)
Changes in Exelon/PHI intercompany money pool	0	68
Other investing activities	5	4
Net cash flows provided by (used in) investing activities	(873)	(752)
Cash flows from financing activities
Issuance of long-term debt	750	350
Retirement of long-term debt	(300)	0
Changes in Exelon/PHI intercompany money pool	(40)	0
Dividends paid on common stock	(254)	(255)
Contributions from parent	414	248
Other financing activities	(8)	(4)
Net cash flows provided by (used in) financing activities	562	339
Increase (decrease) in cash, restricted cash, and cash equivalents	326	222
Cash, restricted cash, and cash equivalents at beginning of period	26	27
Cash, restricted cash, and cash equivalents at end of period	352	249
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	25	28
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	290	273
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	434	405
Deferred income taxes and amortization of investment tax credits	7	35
Other non-cash operating activities	77	82
Changes in assets and liabilities:
Accounts receivable	92	(19)
Change in Receivables From Payables To Affiliates, Net	(13)	(27)
Inventories	(30)	2
Accounts payable and accrued expenses	14	53
Income taxes	3	46
Pension and non-pension postretirement benefit contributions	(76)	(74)
Other assets and liabilities	(129)	(50)
Net cash flows provided by operating activities	669	726
Cash flows from investing activities
Capital expenditures	(907)	(838)
Other investing activities	13	0
Net cash flows provided by (used in) investing activities	(894)	(838)
Cash flows from financing activities
Changes in short-term borrowings	0	(76)
Issuance of long-term debt	600	400
Retirement of long-term debt	(300)	0
Dividends paid on common stock	(219)	(186)
Contributions from parent	257	284
Other financing activities	(6)	(8)
Net cash flows provided by (used in) financing activities	332	414
Increase (decrease) in cash, restricted cash, and cash equivalents	107	302
Cash, restricted cash, and cash equivalents at beginning of period	145	25
Cash, restricted cash, and cash equivalents at end of period	252	327
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(70)	7
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	535	418
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	614	585
Deferred income taxes and amortization of investment tax credits	0	(99)
Other non-cash operating activities	(35)	115
Changes in assets and liabilities:
Accounts receivable	(112)	(121)
Change in Receivables From Payables To Affiliates, Net	(19)	(26)
Inventories	(13)	(2)
Accounts payable and accrued expenses	19	57
Income taxes	17	(14)
Pension and non-pension postretirement benefit contributions	(43)	(35)
Other assets and liabilities	(120)	(61)
Net cash flows provided by operating activities	843	817
Cash flows from investing activities
Capital expenditures	(1,299)	(1,072)
Other investing activities	(1)	3
Net cash flows provided by (used in) investing activities	(1,300)	(1,069)
Cash flows from financing activities
Changes in short-term borrowings	(81)	(208)
Issuance of long-term debt	750	601
Retirement of long-term debt	(255)	(119)
Changes in Exelon/PHI intercompany money pool	(5)	9
Distributions to member	(605)	(451)
Contributions from member	667	493
Other financing activities	(12)	(10)
Net cash flows provided by (used in) financing activities	459	315
Increase (decrease) in cash, restricted cash, and cash equivalents	2	63
Cash, restricted cash, and cash equivalents at beginning of period	160	181
Cash, restricted cash, and cash equivalents at end of period	162	244
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(74)	(5)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	264	227
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	302	282
Deferred income taxes and amortization of investment tax credits	12	(36)
Other non-cash operating activities	(54)	6
Changes in assets and liabilities:
Accounts receivable	(57)	(61)
Change in Receivables From Payables To Affiliates, Net	(2)	(23)
Inventories	(6)	2
Accounts payable and accrued expenses	14	36
Income taxes	(10)	(11)
Pension and non-pension postretirement benefit contributions	(9)	(8)
Other assets and liabilities	(114)	15
Net cash flows provided by operating activities	340	429
Cash flows from investing activities
Capital expenditures	(641)	(512)
Changes in Exelon/PHI intercompany money pool	0	(117)
Other investing activities	(2)	(3)
Net cash flows provided by (used in) investing activities	(643)	(632)
Cash flows from financing activities
Changes in short-term borrowings	5	(82)
Issuance of long-term debt	275	300
Retirement of long-term debt	(1)	(2)
Dividends paid on common stock	(221)	(174)
Contributions from parent	244	262
Other financing activities	(4)	(6)
Net cash flows provided by (used in) financing activities	298	298
Increase (decrease) in cash, restricted cash, and cash equivalents	(5)	95
Cash, restricted cash, and cash equivalents at beginning of period	65	63
Cash, restricted cash, and cash equivalents at end of period	60	158
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(16)	(23)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	135	91
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	157	143
Deferred income taxes and amortization of investment tax credits	5	(20)
Other non-cash operating activities	(2)	47
Changes in assets and liabilities:
Accounts receivable	26	3
Change in Receivables From Payables To Affiliates, Net	(12)	(5)
Inventories	(5)	(3)
Accounts payable and accrued expenses	17	21
Income taxes	19	(12)
Pension and non-pension postretirement benefit contributions	(1)	(1)
Other assets and liabilities	(7)	(25)
Net cash flows provided by operating activities	332	239
Cash flows from investing activities
Capital expenditures	(320)	(278)
Other investing activities	1	(3)
Net cash flows provided by (used in) investing activities	(319)	(281)
Cash flows from financing activities
Changes in short-term borrowings	(124)	(56)
Issuance of long-term debt	125	178
Retirement of long-term debt	0	(79)
Dividends paid on common stock	(106)	(99)
Contributions from parent	120	112
Other financing activities	(4)	(1)
Net cash flows provided by (used in) financing activities	11	55
Increase (decrease) in cash, restricted cash, and cash equivalents	24	13
Cash, restricted cash, and cash equivalents at beginning of period	15	13
Cash, restricted cash, and cash equivalents at end of period	39	26
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(24)	8
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	141	106
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	133	134
Deferred income taxes and amortization of investment tax credits	(20)	(40)
Other non-cash operating activities	(8)	34
Changes in assets and liabilities:
Accounts receivable	(81)	(62)
Change in Receivables From Payables To Affiliates, Net	0	2
Inventories	(1)	0
Accounts payable and accrued expenses	(3)	16
Income taxes	10	4
Pension and non-pension postretirement benefit contributions	(3)	(3)
Other assets and liabilities	15	(53)
Net cash flows provided by operating activities	183	138
Cash flows from investing activities
Capital expenditures	(336)	(281)
Other investing activities	1	5
Net cash flows provided by (used in) investing activities	(335)	(276)
Cash flows from financing activities
Changes in short-term borrowings	38	(70)
Issuance of long-term debt	350	123
Retirement of long-term debt	(254)	(38)
Changes in Exelon/PHI intercompany money pool	0	117
Dividends paid on common stock	(280)	(111)
Contributions from parent	303	117
Other financing activities	(5)	(1)
Net cash flows provided by (used in) financing activities	152	137
Increase (decrease) in cash, restricted cash, and cash equivalents	0	(1)
Cash, restricted cash, and cash equivalents at beginning of period	30	28
Cash, restricted cash, and cash equivalents at end of period	30	27
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (34)	$ 9

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) shares in Millions, $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents		$ 2,957	$ 663
Restricted cash and cash equivalents		473	438
Accounts receivable
Customer accounts receivable		3,530	3,597
Customer allowance for credit losses		(409)	(366)
Customer accounts receivable, net		3,121	3,231
Other accounts receivable		1,616	1,469
Other allowance for credit losses		(77)	(71)
Other accounts receivable, net		1,539	1,398
Mark-to-market derivative assets, current		1,507	644
Unamortized energy contract assets, current		36	38
Inventories, net
Fossil fuel and emission allowances		343	297
Materials and supplies		1,475	1,425
Regulatory assets, current		1,258	1,228
Renewable energy credits, current		492	633
Assets held for sale		11	958
Other		1,665	1,609
Total current assets		14,877	12,562
Accumulated depreciation and amortization		30,049	26,727
Property, plant and equipment, net		82,852	82,584
Deferred debits and other assets
Regulatory assets, noncurrent		8,628	8,759
Nuclear decommissioning trust funds		15,404	14,464
Investments		435	440
Goodwill		6,677	6,677
Mark-to-market derivative assets, noncurrent		665	555
Unamortized energy contract assets, noncurrent		265	294
Other		2,818	2,982
Total deferred debits and other assets		34,892	34,171
Total assets	[1]	132,621	129,317
Current Liabilities
Short-term borrowings		2,667	2,031
Long-term debt due within one year		3,375	1,819
Accounts payable		3,694	3,562
Accrued expenses		1,949	2,078
Payables to affiliates, current		5	5
Regulatory liabilities, current		460	581
Mark-to-market derivative liabilities, current		1,717	295
Unamortized energy contract liabilities, current		92	100
Renewable energy credit obligation		684	661
Liabilities held for sale		3	375
Other		1,180	1,264
Total current liabilities		15,826	12,771
Long-term debt		35,269	35,093
Long-term debt to financing trusts		390	390
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,816	13,035
Asset retirement obligations, noncurrent		12,907	12,300
Pension obligations		3,777	4,503
Non-pension postretirement benefit obligations		1,980	2,011
Spent nuclear fuel obligation		1,209	1,208
Regulatory liabilities, noncurrent		9,448	9,485
Mark-to-market derivative liabilities, noncurrent		721	473
Unamortized energy contract liabilities, noncurrent		169	238
Other		2,850	2,942
Total deferred credits and other liabilities		46,877	46,195
Total liabilities	[1]	98,362	94,449
Commitments and contingencies
Shareholders' equity
Common Stock, No Par Value		$ 0	$ 0
Common stock, shares authorized		2,000	2,000
Common stock, shares outstanding		978	976
Common stock		$ 20,271	$ 19,373
Treasury stock, shares		2	2
Treasury stock, at cost		$ (123)	$ (123)
Retained earnings/Undistributed earnings (losses)		16,926	16,735
Accumulated other comprehensive loss, net		(3,223)	(3,400)
Total shareholders’ equity		33,851	32,585
Member’s equity
Noncontrolling interests		408	2,283
Total equity		34,259	34,868
Total liabilities and shareholders’ equity		132,621	129,317
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		38	98
Restricted cash and cash equivalents		47	47
Accounts receivable
Customer accounts receivable, net		25	148
Unamortized energy contract assets, current		21	22
Inventories, net
Materials and supplies		14	244
Assets held for sale		0	101
Other		517	674
Total current assets		669	1,370
Property, plant and equipment, net		2,052	5,803
Deferred debits and other assets
Nuclear decommissioning trust funds		0	3,007
Unamortized energy contract assets, noncurrent		210	249
Other		22	52
Total assets		2,953	10,481
Current Liabilities
Long-term debt due within one year		80	94
Accounts payable		11	81
Accrued expenses		14	70
Unamortized energy contract liabilities, current		0	4
Liabilities held for sale		0	16
Other		0	5
Total current liabilities		105	270
Long-term debt		832	889
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		149	2,318
Other		3	129
Total liabilities		1,089	3,606
Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		2,722	10,200
Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		1,088	3,598
Exelon Generation Co L L C [Member]
Current Assets
Cash and cash equivalents		1,957	226
Restricted cash and cash equivalents		62	89
Accounts receivable
Customer accounts receivable		1,412	1,330
Customer allowance for credit losses		(84)	(32)
Customer accounts receivable, net		1,328	1,298
Other accounts receivable		465	352
Other allowance for credit losses		(4)	0
Other accounts receivable, net		461	352
Mark-to-market derivative assets, current		1,505	644
Receivables from affiliates, current		184	153
Unamortized energy contract assets, current		36	38
Inventories, net
Fossil fuel and emission allowances		240	233
Materials and supplies		998	978
Renewable energy credits, current		486	621
Assets held for sale		11	958
Other		1,319	1,357
Total current assets		8,587	6,947
Accumulated depreciation and amortization		15,966	13,370
Property, plant and equipment, net		19,574	22,214
Deferred debits and other assets
Nuclear decommissioning trust funds		15,404	14,464
Investments		165	184
Goodwill		47	47
Mark-to-market derivative assets, noncurrent		664	555
Prepaid pension asset		1,702	1,558
Unamortized energy contract assets, noncurrent		265	293
Deferred income taxes		13	6
Other		1,589	1,826
Total deferred debits and other assets		19,849	18,933
Total assets	[2]	48,010	48,094
Current Liabilities
Short-term borrowings		1,380	840
Long-term debt due within one year		1,216	197
Accounts payable		1,612	1,253
Accrued expenses		691	788
Payables to affiliates, current		154	107
Borrowings from Exelon/PHI intercompany money pool		0	285
Mark-to-market derivative liabilities, current		1,709	262
Unamortized energy contract liabilities, current		2	7
Renewable energy credit obligation		682	661
Liabilities held for sale		3	375
Other		347	444
Total current liabilities		7,796	5,219
Long-term debt		4,593	5,566
Long-term debt to affiliates		321	324
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		3,685	3,656
Asset retirement obligations, noncurrent		12,635	12,054
Non-pension postretirement benefit obligations		857	858
Spent nuclear fuel obligation		1,209	1,208
Payables to affiliates, noncurrent		3,143	3,017
Mark-to-market derivative liabilities, noncurrent		511	205
Unamortized energy contract liabilities, noncurrent		1	3
Other		1,224	1,308
Total deferred credits and other liabilities		23,265	22,309
Total liabilities	[2]	35,975	33,418
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		1,185	2,805
Accumulated other comprehensive loss, net		(31)	(30)
Member’s equity
Membership interest		10,480	9,624
Total members' equity		11,634	12,399
Noncontrolling interests		401	2,277
Total equity		12,035	14,676
Total liabilities and shareholders’ equity		48,010	48,094
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		38	98
Restricted cash and cash equivalents		42	44
Accounts receivable
Customer accounts receivable, net		25	148
Unamortized energy contract assets, current		21	22
Inventories, net
Materials and supplies		14	244
Assets held for sale		0	101
Other		513	669
Total current assets		660	1,362
Property, plant and equipment, net		2,052	5,803
Deferred debits and other assets
Nuclear decommissioning trust funds		0	3,007
Unamortized energy contract assets, noncurrent		210	249
Other		13	42
Total assets		2,935	10,463
Current Liabilities
Long-term debt due within one year		70	68
Accounts payable		11	81
Accrued expenses		14	70
Unamortized energy contract liabilities, current		0	4
Liabilities held for sale		0	16
Other		0	5
Total current liabilities		95	244
Long-term debt		832	889
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		149	2,318
Other		3	129
Total liabilities		1,079	3,580
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		2,704	10,182
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		1,078	3,572
Commonwealth Edison Co [Member]
Current Assets
Cash and cash equivalents		241	83
Restricted cash and cash equivalents		276	279
Accounts receivable
Customer accounts receivable		685	656
Customer allowance for credit losses		(88)	(97)
Customer accounts receivable, net		597	559
Other accounts receivable		252	239
Other allowance for credit losses		(19)	(21)
Other accounts receivable, net		233	218
Receivables from affiliates, current		41	22
Inventories, net
Inventories, net		174	170
Regulatory assets, current		287	279
Other		77	49
Total current assets		1,926	1,659
Accumulated depreciation and amortization		5,995	5,672
Property, plant and equipment, net		25,496	24,557
Deferred debits and other assets
Regulatory assets, noncurrent		1,834	1,749
Investments		6	6
Goodwill		2,625	2,625
Receivables from affiliates, noncurrent		2,597	2,541
Prepaid pension asset		1,111	1,022
Other		407	307
Total deferred debits and other assets		8,580	8,250
Total assets		36,002	34,466
Current Liabilities
Short-term borrowings		0	323
Long-term debt due within one year		0	350
Accounts payable		596	683
Accrued expenses		311	390
Payables to affiliates, current		131	96
Customer deposits		97	86
Regulatory liabilities, current		197	289
Mark-to-market derivative liabilities, current		5	33
Other		165	143
Total current liabilities		1,502	2,393
Long-term debt		9,772	8,633
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,629	4,341
Asset retirement obligations, noncurrent		144	126
Non-pension postretirement benefit obligations		183	173
Regulatory liabilities, noncurrent		6,604	6,403
Mark-to-market derivative liabilities, noncurrent		209	268
Other		603	595
Total deferred credits and other liabilities		12,372	11,906
Total liabilities		23,851	23,137
Commitments and contingencies
Shareholders' equity
Common stock		1,588	1,588
Other paid-in capital		8,878	8,285
Retained deficit unappropriated		(1,639)	(1,639)
Retained earnings appropriated		3,324	3,095
Total shareholders’ equity		12,151	11,329
Member’s equity
Total liabilities and shareholders’ equity		36,002	34,466
PECO Energy Co [Member]
Current Assets
Cash and cash equivalents		344	19
Restricted cash and cash equivalents		8	7
Accounts receivable
Customer accounts receivable		411	511
Customer allowance for credit losses		(101)	(116)
Customer accounts receivable, net		310	395
Other accounts receivable		124	130
Other allowance for credit losses		(7)	(8)
Other accounts receivable, net		117	122
Receivables from affiliates, current		9	2
Inventories, net
Fossil fuel and emission allowances		47	33
Materials and supplies		45	38
Prepaid utility taxes		34	0
Regulatory assets, current		35	25
Other		29	21
Total current assets		978	662
Accumulated depreciation and amortization		3,921	3,843
Property, plant and equipment, net		10,841	10,181
Deferred debits and other assets
Regulatory assets, noncurrent		901	776
Investments		34	30
Receivables from affiliates, noncurrent		546	475
Prepaid pension asset		386	375
Other		47	32
Total deferred debits and other assets		1,914	1,688
Total assets		13,733	12,531
Current Liabilities
Long-term debt due within one year		350	300
Accounts payable		487	479
Accrued expenses		168	129
Payables to affiliates, current		60	50
Borrowings from Exelon/PHI intercompany money pool		0	40
Customer deposits		48	59
Regulatory liabilities, current		102	121
Other		31	30
Total current liabilities		1,246	1,208
Long-term debt		3,846	3,453
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,385	2,242
Asset retirement obligations, noncurrent		29	29
Non-pension postretirement benefit obligations		288	286
Regulatory liabilities, noncurrent		588	503
Other		92	93
Total deferred credits and other liabilities		3,382	3,153
Total liabilities		8,658	7,998
Commitments and contingencies
Shareholders' equity
Common stock		3,428	3,014
Retained earnings/Undistributed earnings (losses)		1,647	1,519
Total shareholders’ equity		5,075	4,533
Member’s equity
Total liabilities and shareholders’ equity		13,733	12,531
Baltimore Gas and Electric Company [Member]
Current Assets
Cash and cash equivalents		225	144
Restricted cash and cash equivalents		27	1
Accounts receivable
Customer accounts receivable		351	487
Customer allowance for credit losses		(31)	(35)
Customer accounts receivable, net		320	452
Other accounts receivable		149	117
Other allowance for credit losses		(8)	(9)
Other accounts receivable, net		141	108
Receivables from affiliates, current		2	3
Inventories, net
Fossil fuel and emission allowances		46	25
Materials and supplies		50	41
Regulatory assets, current		185	168
Other		8	6
Total current assets		1,004	948
Accumulated depreciation and amortization		4,212	4,034
Property, plant and equipment, net		10,374	9,872
Deferred debits and other assets
Regulatory assets, noncurrent		468	481
Investments		15	10
Prepaid pension asset		289	270
Other		47	69
Total deferred debits and other assets		819	830
Total assets		12,197	11,650
Current Liabilities
Long-term debt due within one year		250	300
Accounts payable		291	346
Accrued expenses		204	205
Payables to affiliates, current		49	61
Customer deposits		98	110
Regulatory liabilities, current		34	30
Other		81	91
Total current liabilities		1,007	1,143
Long-term debt		3,710	3,364
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,656	1,521
Asset retirement obligations, noncurrent		26	23
Non-pension postretirement benefit obligations		177	189
Regulatory liabilities, noncurrent		989	1,109
Other		107	104
Total deferred credits and other liabilities		2,955	2,946
Total liabilities		7,672	7,453
Commitments and contingencies
Shareholders' equity
Common stock		2,575	2,318
Retained earnings/Undistributed earnings (losses)		1,950	1,879
Total shareholders’ equity		4,525	4,197
Member’s equity
Total liabilities and shareholders’ equity		12,197	11,650
Pepco Holdings LLC [Member]
Current Assets
Cash and cash equivalents		82	111
Restricted cash and cash equivalents		71	39
Accounts receivable
Customer accounts receivable		671	611
Customer allowance for credit losses		(105)	(86)
Customer accounts receivable, net		566	525
Other accounts receivable		300	260
Other allowance for credit losses		(40)	(33)
Other accounts receivable, net		260	227
Receivables from affiliates, current		3	8
Inventories, net
Fossil fuel and emission allowances		10	6
Materials and supplies		207	198
Regulatory assets, current		434	440
Other		57	45
Total current assets		1,690	1,599
Accumulated depreciation and amortization		1,995	1,811
Property, plant and equipment, net		16,163	15,377
Deferred debits and other assets
Regulatory assets, noncurrent		1,848	1,933
Investments		146	140
Goodwill		4,005	4,005
Prepaid pension asset		357	365
Deferred income taxes		10	10
Other		283	307
Total deferred debits and other assets		6,649	6,760
Total assets	[3]	24,502	23,736
Current Liabilities
Short-term borrowings		287	368
Long-term debt due within one year		405	347
Accounts payable		479	539
Accrued expenses		300	299
Payables to affiliates, current		80	104
Borrowings from Exelon/PHI intercompany money pool		16	21
Customer deposits		82	106
Regulatory liabilities, current		122	137
Unamortized energy contract liabilities, current		90	92
Other		154	141
Total current liabilities		2,015	2,154
Long-term debt		7,077	6,659
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,635	2,439
Asset retirement obligations, noncurrent		69	59
Non-pension postretirement benefit obligations		71	86
Regulatory liabilities, noncurrent		1,237	1,438
Unamortized energy contract liabilities, noncurrent		168	235
Other		589	622
Total deferred credits and other liabilities		4,769	4,879
Total liabilities	[3]	13,861	13,692
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		(138)	(68)
Member’s equity
Membership interest		10,779	10,112
Total members' equity		10,641	10,044
Total equity		10,641	10,044
Total liabilities and shareholders’ equity		24,502	23,736
Pepco Holdings LLC [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		5	3
Accounts receivable
Customer accounts receivable, net		0	0
Unamortized energy contract assets, current		0	0
Inventories, net
Materials and supplies		0	0
Assets held for sale		0	0
Other		4	5
Total current assets		9	8
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Unamortized energy contract assets, noncurrent		0	0
Other		9	10
Total assets		18	18
Current Liabilities
Long-term debt due within one year		10	26
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities, current		0	0
Liabilities held for sale		0	0
Other		0	0
Total current liabilities		10	26
Long-term debt		0	0
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total liabilities		10	26
Pepco Holdings LLC [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		18	18
Pepco Holdings LLC [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		10	26
Potomac Electric Power Company [Member]
Current Assets
Cash and cash equivalents		19	30
Restricted cash and cash equivalents		41	35
Accounts receivable
Customer accounts receivable		306	279
Customer allowance for credit losses		(41)	(32)
Customer accounts receivable, net		265	247
Other accounts receivable		166	131
Other allowance for credit losses		(17)	(13)
Other accounts receivable, net		149	118
Receivables from affiliates, current		0	2
Inventories, net
Inventories, net		117	111
Regulatory assets, current		215	214
Other		12	13
Total current assets		818	770
Accumulated depreciation and amortization		3,831	3,697
Property, plant and equipment, net		7,919	7,456
Deferred debits and other assets
Regulatory assets, noncurrent		548	570
Investments		120	115
Prepaid pension asset		280	284
Other		63	69
Total deferred debits and other assets		1,011	1,038
Total assets		9,748	9,264
Current Liabilities
Short-term borrowings		40	35
Long-term debt due within one year		313	3
Accounts payable		218	226
Accrued expenses		149	164
Payables to affiliates, current		51	55
Customer deposits		37	51
Regulatory liabilities, current		27	46
Merger related obligation		29	33
Current portion of DC PLUG obligation		30	30
Other		22	31
Total current liabilities		916	674
Long-term debt		3,128	3,162
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,289	1,189
Asset retirement obligations, noncurrent		45	39
Non-pension postretirement benefit obligations		5	13
Regulatory liabilities, noncurrent		555	644
Other		320	340
Total deferred credits and other liabilities		2,214	2,225
Total liabilities		6,258	6,061
Commitments and contingencies
Shareholders' equity
Common stock		2,302	2,058
Retained earnings/Undistributed earnings (losses)		1,188	1,145
Total shareholders’ equity		3,490	3,203
Member’s equity
Total liabilities and shareholders’ equity		9,748	9,264
Delmarva Power and Light Company [Member]
Current Assets
Cash and cash equivalents		13	15
Restricted cash and cash equivalents		26	0
Accounts receivable
Customer accounts receivable		135	176
Customer allowance for credit losses		(18)	(22)
Customer accounts receivable, net		117	154
Other accounts receivable		59	68
Other allowance for credit losses		(8)	(9)
Other accounts receivable, net		51	59
Receivables from affiliates, current		1	1
Inventories, net
Fossil fuel and emission allowances		10	6
Materials and supplies		52	51
Prepaid utility taxes		16	11
Regulatory assets, current		72	58
Renewable energy credits, current		3	10
Other		4	3
Total current assets		365	368
Accumulated depreciation and amortization		1,608	1,533
Property, plant and equipment, net		4,485	4,314
Deferred debits and other assets
Regulatory assets, noncurrent		219	222
Goodwill		8	8
Prepaid pension asset		158	162
Other		60	66
Total deferred debits and other assets		445	458
Total assets		5,295	5,140
Current Liabilities
Short-term borrowings		22	146
Long-term debt due within one year		83	82
Accounts payable		107	126
Accrued expenses		61	46
Payables to affiliates, current		24	36
Customer deposits		27	32
Regulatory liabilities, current		49	47
Other		41	20
Total current liabilities		414	535
Long-term debt		1,725	1,595
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		761	715
Asset retirement obligations, noncurrent		16	14
Non-pension postretirement benefit obligations		12	15
Regulatory liabilities, noncurrent		446	493
Other		95	97
Total deferred credits and other liabilities		1,330	1,334
Total liabilities		3,469	3,464
Commitments and contingencies
Shareholders' equity
Common stock		1,209	1,089
Retained earnings/Undistributed earnings (losses)		617	587
Total shareholders’ equity		1,826	1,676
Member’s equity
Total liabilities and shareholders’ equity		5,295	5,140
Atlantic City Electric Company [Member]
Current Assets
Cash and cash equivalents		16	17
Restricted cash and cash equivalents		5	3
Accounts receivable
Customer accounts receivable		230	156
Customer allowance for credit losses		(46)	(32)
Customer accounts receivable, net		184	124
Other accounts receivable		75	72
Other allowance for credit losses		(15)	(11)
Other accounts receivable, net		60	61
Receivables from affiliates, current		1	6
Inventories, net
Inventories, net		38	37
Prepaid utility taxes		10	0
Regulatory assets, current		57	75
Other		5	3
Total current assets		376	326
Accumulated depreciation and amortization		1,390	1,303
Property, plant and equipment, net		3,649	3,475
Deferred debits and other assets
Regulatory assets, noncurrent		428	395
Prepaid pension asset		31	40
Other		48	50
Total deferred debits and other assets		507	485
Total assets	[4]	4,532	4,286
Current Liabilities
Short-term borrowings		225	187
Long-term debt due within one year		8	261
Accounts payable		146	177
Accrued expenses		43	46
Payables to affiliates, current		26	31
Customer deposits		19	23
Regulatory liabilities, current		46	44
Other		15	11
Total current liabilities		528	780
Long-term debt		1,502	1,152
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		671	624
Non-pension postretirement benefit obligations		13	17
Regulatory liabilities, noncurrent		211	274
Other		52	48
Total deferred credits and other liabilities		947	963
Total liabilities	[4]	2,977	2,895
Commitments and contingencies
Shareholders' equity
Common stock		1,574	1,271
Retained earnings/Undistributed earnings (losses)		(19)	120
Total shareholders’ equity		1,555	1,391
Member’s equity
Total liabilities and shareholders’ equity		4,532	4,286
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		5	3
Accounts receivable
Customer accounts receivable, net		0	0
Unamortized energy contract assets, current		0	0
Inventories, net
Materials and supplies		0	0
Assets held for sale		0	0
Other		0	0
Total current assets		5	3
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Unamortized energy contract assets, noncurrent		0	0
Other		9	10
Total assets		14	13
Current Liabilities
Long-term debt due within one year		6	21
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities, current		0	0
Liabilities held for sale		0	0
Other		0	0
Total current liabilities		6	21
Long-term debt		0	0
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total liabilities		6	21
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		14	13
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		$ 6	$ 21

[1]	Exelon’s consolidated assets include $2,722 million and $10,200 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $1,088 million and $3,598 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 17 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $2,704 million and $10,182 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $1,078 million and $3,572 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 17 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both September 30, 2021 and December 31, 2020 of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $10 million and $26 million at September 30, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 17 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $14 million and $13 million at September 30, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $6 million and $21 million at September 30, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 17 — Variable Interest Entities for additional information.

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Correcting Adjustment [Member]	Common Stock [Member]	Common Stock [Member]Correcting Adjustment [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member]Retained Earnings [Member]	Exelon Generation Co L L C [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]Noncontrolling Interest [Member]	Exelon Generation Co L L C [Member]Membership Interest [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Other Paid-in-Capital [Member]	Commonwealth Edison Co [Member]Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member]Retained Earnings, Appropriated	PECO Energy Co [Member]	PECO Energy Co [Member]Common Stock [Member]	PECO Energy Co [Member]Retained Earnings [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member]Retained Earnings [Member]	Pepco Holdings LLC [Member]Membership Interest [Member]	Potomac Electric Power Company [Member]	Potomac Electric Power Company [Member]Common Stock [Member]	Potomac Electric Power Company [Member]Retained Earnings [Member]	Delmarva Power and Light Company [Member]	Delmarva Power and Light Company [Member]Common Stock [Member]	Delmarva Power and Light Company [Member]Retained Earnings [Member]	Atlantic City Electric Company [Member]	Atlantic City Electric Company [Member]Common Stock [Member]	Atlantic City Electric Company [Member]Retained Earnings [Member]
Beginning balance (in shares) at Dec. 31, 2019	974,416
Beginning balance at Dec. 31, 2019	$ 34,573		$ 19,274		$ (123)	$ 16,267	$ (3,194)	$ 2,349
Beginning Balance at Dec. 31, 2019									$ 15,830	$ 3,950	$ (32)	$ 2,346	$ 9,566												$ 9,608	$ (10)	$ 9,618
Beginning Balance at Dec. 31, 2019														$ 10,677	$ 1,588	$ 7,572	$ (1,639)	$ 3,156	$ 4,178	$ 2,766	$ 1,412	$ 3,683	$ 1,907	$ 1,776				$ 2,907	$ 1,796	$ 1,111	$ 1,580	$ 977	$ 603	$ 1,276	$ 1,154	$ 122
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 376					582		(206)	(161)	45		(206)		168			168		140		140	181		181	108	108		52		52	45		45	13		13
Appropriation of retained earnings for future dividends														0			(168)	168
Long -Term Incentive Plan Activity (shares)	1,354
Long-Term Incentive Plan Activity		$ (4)		$ (4)
Employee stock purchase plan issuances (shares)	470
Employee stock purchase plan issuances	$ 31		31
Changes in equity of noncontrolling interests	(9)							(9)	(11)			(11)
Sale of noncontrolling interests	2		2						2				2
Common stock dividends	(374)					(374)								(125)				(125)	(85)		(85)	(62)		(62)				(28)		(28)	(52)		(52)	(23)		(23)
Distributions to member									(468)	(468)															(134)	(134)
Contributions from parent														125		125			231	231					144		144	137	137		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 21						21		(9)	0	(9)	0
Ending balance (in shares) at Mar. 31, 2020	976,240
Ending balance at Mar. 31, 2020	$ 34,616		19,303		(123)	16,475	(3,173)	2,134
Ending Balance at Mar. 31, 2020									15,183	3,527	(41)	2,129	9,568												9,726	(36)	9,762
Ending Balance at Mar. 31, 2020														10,845	1,588	7,697	(1,639)	3,199	4,464	2,997	1,467	3,802	1,907	1,895				3,068	1,933	1,135	1,579	983	596	1,267	1,155	112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Beginning balance (in shares) at Dec. 31, 2019	974,416
Beginning balance at Dec. 31, 2019	$ 34,573		19,274		(123)	16,267	(3,194)	2,349
Beginning Balance at Dec. 31, 2019									15,830	3,950	(32)	2,346	9,566												9,608	(10)	9,618
Beginning Balance at Dec. 31, 2019														10,677	1,588	7,572	(1,639)	3,156	4,178	2,766	1,412	3,683	1,907	1,776				2,907	1,796	1,111	1,580	977	603	1,276	1,154	122
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,519								485					304					317			273			418			227			91			106
Acquisition of CENG noncontrolling interest	0								0
Other comprehensive income (loss), net of income taxes	$ 90						90		(4)
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103		19,362		(123)	16,749	(3,104)	2,219
Ending Balance at Sep. 30, 2020									14,924	3,114	(36)	2,213	9,633												10,069	(43)	10,112
Ending Balance at Sep. 30, 2020														11,095	1,588	8,060	(1,700)	3,147	4,488	3,014	1,474	4,054	2,191	1,863				3,222	2,058	1,164	1,684	1,089	595	1,388	1,271	117
Beginning balance (in shares) at Mar. 31, 2020	976,240
Beginning balance at Mar. 31, 2020	$ 34,616		19,303		(123)	16,475	(3,173)	2,134
Beginning Balance at Mar. 31, 2020									15,183	3,527	(41)	2,129	9,568												9,726	(36)	9,762
Beginning Balance at Mar. 31, 2020														10,845	1,588	7,697	(1,639)	3,199	4,464	2,997	1,467	3,802	1,907	1,895				3,068	1,933	1,135	1,579	983	596	1,267	1,155	112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 574					521		53	529	476		53		(61)			(61)		39		39	39		39	94	94		57		57	19		19	18		18
Long -Term Incentive Plan Activity (shares)	148
Long-Term Incentive Plan Activity	$ 17		17
Employee stock purchase plan issuances (shares)		(51)
Employee stock purchase plan issuances	15		15
Changes in equity of noncontrolling interests	(19)							(19)	(19)			(19)
Sale of noncontrolling interests	1		1						1				1
Common stock dividends	(374)					(374)								(124)				(124)	(85)		(85)	(62)		(62)				(73)		(73)	(14)		(14)	(12)		(12)
Distributions to member									(469)	(469)															(134)	(134)
Contributions from parent														124		124						26	26		215		215				100	100		115	115
Other comprehensive income (loss), net of income taxes	$ 41						41		2	0	2	0
Ending balance (in shares) at Jun. 30, 2020	976,337
Ending balance at Jun. 30, 2020	$ 34,871		19,336		(123)	16,622	(3,132)	2,168
Ending Balance at Jun. 30, 2020									15,227	3,534	(39)	2,163	9,569												9,901	(76)	9,977
Ending Balance at Jun. 30, 2020														10,784	1,588	7,821	(1,700)	3,075	4,418	2,997	1,421	3,805	1,933	1,872				3,052	1,933	1,119	1,684	1,083	601	1,388	1,270	118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Net income (loss)	$ 569					501		68	117	49		68		196			196		138		138	53		53	216	216		118		118	27		27	75		75
Appropriation of retained earnings for future dividends														0			(196)	196
Long -Term Incentive Plan Activity (shares)	68
Long-Term Incentive Plan Activity	$ 10		10
Employee stock purchase plan issuances (shares)	1,000
Employee stock purchase plan issuances	$ 16		16
Changes in equity of noncontrolling interests	(17)							(17)	(18)			(18)
Common stock dividends	(374)					(374)								(124)				(124)	(85)		(85)	(62)		(62)				(73)		(73)	(33)		(33)	(76)		(76)
Distributions to member									(469)	(469)															(183)	(183)
Contributions from parent									64				64	239		239			17	17		258	258		135		135	125	125		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 28						28	0	3	0	3	0
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103		19,362		(123)	16,749	(3,104)	2,219
Ending Balance at Sep. 30, 2020									14,924	3,114	(36)	2,213	9,633												10,069	(43)	10,112
Ending Balance at Sep. 30, 2020														11,095	1,588	8,060	(1,700)	3,147	4,488	3,014	1,474	4,054	2,191	1,863				3,222	2,058	1,164	1,684	1,089	595	1,388	1,271	117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Appropriation of retained earnings for future dividends														3,095
Beginning balance (in shares) at Dec. 31, 2020	977,466
Beginning balance at Dec. 31, 2020	$ 34,868		19,373		(123)	16,735	(3,400)	2,283
Beginning Balance at Dec. 31, 2020									14,676	2,805	(30)	2,277	9,624												10,044	(68)	10,112
Beginning Balance at Dec. 31, 2020	32,585													11,329	1,588	8,285	(1,639)	3,095	4,533	3,014	1,519	4,197	2,318	1,879				3,203	2,058	1,145	1,676	1,089	587	1,391	1,271	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (264)					(289)		25	(769)	(793)		24		197			197		167		167	209		209	128	128		59		59	56		56	14		14
Appropriation of retained earnings for future dividends														0			(197)	197
Long -Term Incentive Plan Activity (shares)	640
Long-Term Incentive Plan Activity	$ 5		5
Employee stock purchase plan issuances (shares)	902
Employee stock purchase plan issuances	$ 34		34
Changes in equity of noncontrolling interests	(10)							(10)	(10)			(10)
Common stock dividends	(374)					(374)								(127)				(127)	(85)		(85)	(74)		(74)				(28)		(28)	(40)		(40)	(14)		(14)
Distributions to member									(458)	(458)															(81)	(81)
Contributions from parent														198		198									560		560	138	138		120	120		303	303
Other comprehensive income (loss), net of income taxes	$ 54						54		1	0	1	0
Ending balance (in shares) at Mar. 31, 2021	979,008
Ending balance at Mar. 31, 2021	$ 34,313		19,412		(123)	16,072	(3,346)	2,298
Ending Balance at Mar. 31, 2021									13,440	1,554	(29)	2,291	9,624												10,651	(21)	10,672
Ending Balance at Mar. 31, 2021														11,597	1,588	8,483	(1,639)	3,165	4,615	3,014	1,601	4,332	2,318	2,014				3,372	2,196	1,176	1,812	1,209	603	1,694	1,574	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Beginning balance (in shares) at Dec. 31, 2020	977,466
Beginning balance at Dec. 31, 2020	$ 34,868		19,373		(123)	16,735	(3,400)	2,283
Beginning Balance at Dec. 31, 2020									14,676	2,805	(30)	2,277	9,624												10,044	(68)	10,112
Beginning Balance at Dec. 31, 2020	32,585													11,329	1,588	8,285	(1,639)	3,095	4,533	3,014	1,519	4,197	2,318	1,879				3,203	2,058	1,145	1,676	1,089	587	1,391	1,271	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,441								(122)					609					383			290			535			264			135			141
Acquisition of CENG noncontrolling interest	885								885
Other comprehensive income (loss), net of income taxes	$ 177						177		(1)
Ending balance (in shares) at Sep. 30, 2021	980,150
Ending balance at Sep. 30, 2021	$ 34,259		20,271		(123)	16,926	(3,223)	408
Ending Balance at Sep. 30, 2021									12,035	1,185	(31)	401	10,480												10,641	(138)	10,779
Ending Balance at Sep. 30, 2021	$ 33,851													12,151	1,588	8,878	(1,639)	3,324	5,075	3,428	1,647	4,525	2,575	1,950				3,490	2,302	1,188	1,826	1,209	617	1,555	1,574	(19)
Beginning balance (in shares) at Mar. 31, 2021	979,008
Beginning balance at Mar. 31, 2021	$ 34,313		19,412		(123)	16,072	(3,346)	2,298
Beginning Balance at Mar. 31, 2021									13,440	1,554	(29)	2,291	9,624												10,651	(21)	10,672
Beginning Balance at Mar. 31, 2021														11,597	1,588	8,483	(1,639)	3,165	4,615	3,014	1,601	4,332	2,318	2,014				3,372	2,196	1,176	1,812	1,209	603	1,694	1,574	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 476					401		75	13	(61)		74		192			192		104		104	45		45	141	141		75		75	30		30	37		37
Appropriation of retained earnings for future dividends														0			(192)	192
Long -Term Incentive Plan Activity (shares)	237
Long-Term Incentive Plan Activity	$ 24		24
Employee stock purchase plan issuances (shares)	420
Employee stock purchase plan issuances	$ 18		18
Changes in equity of noncontrolling interests	(13)							(13)	(12)			(12)
Common stock dividends	(375)					(375)								(126)				(126)	(84)		(84)	(72)		(72)				(95)		(95)	(23)		(23)	(215)		(215)
Distributions to member									(458)	(458)															(333)	(333)
Contributions from parent														197		197			395	395
Other comprehensive income (loss), net of income taxes	$ 57						57		2	0	2	0
Ending balance (in shares) at Jun. 30, 2021	979,665
Ending balance at Jun. 30, 2021	$ 34,500		19,454		(123)	16,098	(3,289)	2,360
Ending Balance at Jun. 30, 2021									12,985	1,035	(27)	2,353	9,624												10,459	(213)	10,672
Ending Balance at Jun. 30, 2021														11,860	1,588	8,680	(1,639)	3,231	5,030	3,409	1,621	4,305	2,318	1,987				3,352	2,196	1,156	1,819	1,209	610	1,516	1,574	(58)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Net income (loss)	$ 1,229					1,203		26	633	607		26		220			220		111		111	36		36	266	266		130		130	50		50	90		90
Appropriation of retained earnings for future dividends														0			(220)	220
Long -Term Incentive Plan Activity (shares)	94
Long-Term Incentive Plan Activity	$ 9		9
Employee stock purchase plan issuances (shares)	391
Employee stock purchase plan issuances	$ 18		18
Changes in equity of noncontrolling interests	(13)							(13)	(13)			(13)
Acquisition of CENG noncontrolling interest	(885)		1,080					(1,965)	(885)			(1,965)	1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest	(290)		(290)						(288)				(288)
Common stock dividends	(375)					(375)								(127)				(127)	(85)		(85)	(73)		(73)				(98)		(98)	(43)		(43)	(51)		(51)
Distributions to member									(457)	(457)															(191)	(191)
Contributions from parent									64				64	198		198			19	19		257	257		107		107	106	106
Other comprehensive income (loss), net of income taxes	$ 66						66		(4)	0	(4)	0
Ending balance (in shares) at Sep. 30, 2021	980,150
Ending balance at Sep. 30, 2021	$ 34,259		$ 20,271		$ (123)	$ 16,926	$ (3,223)	$ 408
Ending Balance at Sep. 30, 2021									$ 12,035	$ 1,185	$ (31)	$ 401	$ 10,480												$ 10,641	$ (138)	$ 10,779
Ending Balance at Sep. 30, 2021	$ 33,851													12,151	$ 1,588	$ 8,878	$ (1,639)	$ 3,324	$ 5,075	$ 3,428	$ 1,647	$ 4,525	$ 2,575	$ 1,950				$ 3,490	$ 2,302	$ 1,188	$ 1,826	$ 1,209	$ 617	$ 1,555	$ 1,574	$ (19)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Appropriation of retained earnings for future dividends														$ 3,324

Significant Accounting Policies

Significant Accounting Policies (All Registrants)	9 Months Ended
Significant Accounting Policies (All Registrants)	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Significant Accounting Policies (All Registrants) Description of Business (All Registrants) Exelon is a utility services holding company engaged in the generation, delivery and marketing of energy through Generation and the energy distribution and transmission businesses through ComEd, PECO, BGE, Pepco, DPL, and ACE. Name of Registrant Business Service Territories Exelon Generation Generation, physical delivery and marketing of power across multiple geographical regions through its customer-facing business, Constellation, which sells electricity to both wholesale and retail customers. Generation also sells natural gas, renewable energy, and other energy-related products and services. Five reportable segments: Mid-Atlantic, Midwest, New York, ERCOT, and Other Power Regions Commonwealth Edison Company Purchase and regulated retail sale of electricity Northern Illinois, including the City of Chicago Transmission and distribution of electricity to retail customers PECO Energy Company Purchase and regulated retail sale of electricity and natural gas Southeastern Pennsylvania, including the City of Philadelphia (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Pennsylvania counties surrounding the City of Philadelphia (natural gas) Baltimore Gas and Electric Company Purchase and regulated retail sale of electricity and natural gas Central Maryland, including the City of Baltimore (electricity and natural gas) Transmission and distribution of electricity and distribution of natural gas to retail customers Pepco Holdings LLC Utility services holding company engaged, through its reportable segments Pepco, DPL, and ACE Service Territories of Pepco, DPL, and ACE Potomac Electric Purchase and regulated retail sale of electricity District of Columbia, and major portions of Montgomery and Prince George’s Counties, Maryland Transmission and distribution of electricity to retail customers Delmarva Power & Purchase and regulated retail sale of electricity and natural gas Portions of Delaware and Maryland (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Portions of New Castle County, Delaware (natural gas) Atlantic City Electric Company Purchase and regulated retail sale of electricity Portions of Southern New Jersey Transmission and distribution of electricity to retail customers Basis of Presentation (All Registrants) This is a combined quarterly report of all Registrants. The Notes to the Consolidated Financial Statements apply to the Registrants as indicated parenthetically next to each corresponding disclosure. When appropriate, the Registrants are named specifically for their related activities and disclosures. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology, and supply management services. PHI also has a business services subsidiary, PHISCO, which provides a variety of support services at cost, including legal, accounting, engineering, customer operations, distribution and transmission planning, asset management, system operations, and power procurement, to PHI operating companies. The costs of BSC and PHISCO are directly charged or allocated to the applicable subsidiaries. The results of Exelon’s corporate operations are presented as “Other” in the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 and 2020 are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature,

Mergers, Acquisitions, and Disp

Mergers, Acquisitions, and Dispositions (Exelon and Generation)	9 Months Ended
	Sep. 30, 2021
Mergers, Acquisitions, and Dispositions [Abstract]
Mergers, Acquisitions, and Dispositions (Exelon and Generation)	Mergers, Acquisitions, and Dispositions (Exelon and Generation) CENG Put Option (Exelon and Generation) Prior to August 6, 2021, Generation owned a 50.01% membership interest in CENG, a joint venture with EDF, which wholly owns the Calvert Cliffs and Ginna nuclear stations and Nine Mile Point Unit 1, in addition to an 82% undivided ownership interest in Nine Mile Point Unit 2. CENG is 100% consolidated in Exelon's and Generation's financial statements. See Note 17 — Variable Interest Entities for additional information. On April 1, 2014, Generation and EDF entered into various agreements including a NOSA, an amended LLC Operating Agreement, an Employee Matters Agreement, and a Put Option Agreement, among others. Under the amended LLC Operating Agreement, CENG made a $400 million special distribution to EDF and committed to make preferred distributions to Generation until Generation has received aggregate distributions of $400 million plus a return of 8.50% per annum. Under the terms of the Put Option Agreement, EDF had the option to sell its 49.99% equity interest in CENG to Generation exercisable beginning on January 1, 2016 and thereafter until June 30, 2022. On November 20, 2019, Generation received notice of EDF’s intention to exercise the put option to sell its interest in CENG to Generation, and the put automatically exercised on January 19, 2020 at the end of the sixty-day advance notice period. The transaction required approval by FERC and the NYPSC, which approvals were received on July 30, 2020 and April 15, 2021, respectively. On August 6, 2021, Generation and EDF entered into a settlement agreement pursuant to which Generation purchased EDF’s equity interest in CENG for a net purchase price of $885 million, which includes, among other things, an adjustment for EDF’s share of the balance of the preferred distribution payable by CENG to Generation. The difference between the net purchase price and EDF’s Noncontrolling Interest as of August 6, 2021 was recorded in Common Stock in Exelon’s Consolidated Balance Sheet and Membership Interest in Generation’s Consolidated Balance Sheet. As a result of the transaction, Exelon and Generation recorded deferred tax liabilities of $290 million and $288 million, respectively, in Common Stock in Exelon’s Consolidated Balance Sheet and Membership Interest in Generation’s Consolidated Balance Sheet. See Note 10 — Income Taxes for additional information. The following tables summarize the effects of the changes in Generation's ownership interest in CENG in Exelon's Shareholders' Equity and Generation's Member's Equity: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Net income attributable to Exelon's common shareholders $ 1,203 $ 1,315 Pre-tax increase in Exelon's common stock for purchase of EDF's 49.99% equity interest (a) 1,080 1,080 Decrease in Exelon's common stock due to deferred tax liabilities resulting from purchase of EDF's 49.99% equity interest (a) (290) (290) Change from net income attributable to common stock and transfers from noncontrolling interest $ 1,993 $ 2,105 Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Net income (loss) attributable to Generation's membership interest $ 607 $ (247) Pre-tax increase in Generation's membership interest for purchase of EDF's 49.99% equity interest (a) 1,080 1,080 Decrease in Generation's membership interest due to deferred tax liabilities resulting from purchase of EDF's 49.99% equity interest (a) (288) (288) Change from net income (loss) attributable to membership interest and transfers from noncontrolling interest $ 1,399 $ 545 _________ (a) Represents non-cash activity in Exelon’s and Generation’s consolidated financial statements. Agreement for Sale of Generation’s Solar Business (Exelon and Generation) On December 8, 2020, Generation entered into an agreement with an affiliate of Brookfield Renewable, for the sale of a significant portion of Generation’s solar business, including 360 MW of generation in operation or under construction across more than 600 sites across the United States. Generation will retain certain solar assets not included in this agreement, primarily Antelope Valley. Completion of the transaction contemplated by the sale agreement was subject to the satisfaction of several closing conditions which were satisfied in the first quarter of 2021. The sale was completed on March 31, 2021 for a purchase price of $810 million. Generation received cash proceeds of $675 million, net of $125 million long-term debt assumed by the buyer and certain working capital and other post-closing adjustments. Exelon and Generation recognized a pre-tax gain of $68 million which is included in Gain on sales of assets and businesses in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Debt and Credit Agreements of the Exelon 2020 Form 10-K for additional information on the SolGen nonrecourse debt included as part of the transaction. Agreement for the Sale of a Generation Biomass Facility (Exelon and Generation) On April 28, 2021, Generation and ReGenerate Energy Holdings, LLC (“ReGenerate”) entered into a purchase agreement, under which ReGenerate agreed to purchase Generation’s interest in the Albany Green Energy biomass facility. As a result, in the second quarter of 2021, Exelon and Generation recorded a pre-tax impairment charge of $140 million in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Completion of the transaction was subject to the satisfaction of various customary closing conditions which were satisfied in the second quarter of 2021. The sale was completed on June 30, 2021 for a net purchase price of $36 million.

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	9 Months Ended
Regulatory Matters (All Registrants)	Sep. 30, 2021
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	Regulatory Matters (All Registrants) As discussed in Note 3 — Regulatory Matters of the Exelon 2020 Form 10-K, the Registrants are involved in rate and regulatory proceedings at FERC and their state commissions. The following discusses developments in 2021 and updates to the 2020 Form 10-K. Utility Regulatory Matters (Exelon, PHI, and the Utility Registrants) Distribution Base Rate Case Proceedings The following tables show the completed and pending distribution base rate case proceedings in 2021. Completed Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Service Requested Revenue Requirement (Decrease) Increase Approved Revenue Requirement (Decrease) Increase Approved ROE Approval Date Rate Effective Date ComEd - Illinois (a) April 16, 2020 Electric $ (11) $ (14) 8.38 % December 9, 2020 January 1, 2021 PECO - Pennsylvania September 30, 2020 Natural Gas 69 29 10.24 % June 22, 2021 July 1, 2021 BGE - Maryland (b) May 15, 2020 (amended September 11, 2020) Electric 203 140 9.50 % December 16, 2020 January 1, 2021 Natural Gas 108 74 9.65 % Pepco - District of Columbia (c) May 30, 2019 (amended June 1, 2020) Electric 136 109 9.275 % June 8, 2021 July 1, 2021 Pepco - Maryland (d) October 26, 2020 (amended March 31, 2021) Electric 104 52 9.55 % June 28, 2021 June 28, 2021 DPL - Delaware March 6, 2020 (amended February 2, 2021) Electric 23 14 9.60 % September 15, 2021 October 6, 2020 ACE - New Jersey (e) December 9, 2020 (amended February 26, 2021) Electric 67 41 9.60 % July 14, 2021 January 1, 2022 __________ (a) ComEd's 2021 approved revenue requirement reflects an increase of $50 million for the initial year revenue requirement for 2021 and a decrease of $64 million related to the annual reconciliation for 2019. The revenue requirement for 2021 and the revenue requirement for 2019 provide for a weighted average debt and equity return on distribution rate base of 6.28%, inclusive of an allowed ROE of 8.38%, reflecting the monthly average yields for 30-year treasury bonds plus 580 basis points. (b) Reflects a three-year cumulative multi-year plan for 2021 through 2023. The MDPSC awarded BGE electric revenue requirement increases of $59 million, $39 million, and $42 million, before offsets, in 2021, 2022, and 2023, respectively, and natural gas revenue requirement increases of $53 million, $11 million, and $10 million, before offsets, in 2021, 2022, and 2023, respectively. BGE proposed to use certain tax benefits to fully offset the increases in 2021 and 2022 and partially offset the increase in 2023. However, the MDPSC only utilized the tax benefits to fully offset the increases in 2021 such that customer rates will remain unchanged from 2020 to 2021. The MDPSC has deferred a decision on whether to use certain tax benefits to offset the customer rate increases in 2022 and 2023 and BGE cannot predict the outcome. (c) Reflects a cumulative multi-year plan with 18-months remaining in 2021 through 2022. The DCPSC awarded Pepco electric incremental revenue requirement increases of $42 million and $67 million, before offsets, for the remainder of 2021 and 2022, respectively. However, the DCPSC utilized the acceleration of refunds for certain tax benefits along with other rate relief to partially offset the customer rate increases by $22 million and $40 million for the remainder of 2021 and 2022, respectively. (d) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024. The MDPSC awarded Pepco electric incremental revenue requirement increases of $21 million, $16 million, and $15 million, before offsets, for the 12-month periods ending March 31, 2022, 2023, and 2024, respectively. Pepco proposed to utilize certain tax benefits to fully offset the increase through 2023 and partially offset customer rate increases in 2024. However, the MDPSC only utilized the acceleration of refunds for certain tax benefits to fully offset the increases such that customer rates remain unchanged through March 31, 2022. The MDPSC has deferred decision on whether to use additional tax benefits to offset customer rate increases for periods after March 31, 2022 and Pepco cannot predict the outcome. (e) Requested and approved increases are before New Jersey sales and use tax. The order allows ACE to retain approximately $11 million of certain tax benefits which resulted in a decrease to income tax expense in Exelon's, PHI's, and ACE's Consolidated Statements of Operations and Comprehensive Income in the third quarter of 2021. Pending Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Service Requested Revenue Requirement Increase Requested ROE Expected Approval Timing ComEd - Illinois (a) April 16, 2021 Electric $ 51 7.36 % Fourth quarter of 2021 PECO - Pennsylvania (b) March 30, 2021 Electric 246 10.95 % Fourth quarter of 2021 DPL - Maryland September 1, 2021 Electric 29 10.10 % First quarter of 2022 __________ (a) ComEd's 2022 requested revenue requirement reflects an increase of $40 million for the initial year revenue requirement for 2022 and an increase of $11 million related to the annual reconciliation for 2020. The revenue requirement for 2022 provides for a weighted average debt and equity return on distribution rate base of 5.72%, inclusive of an allowed ROE of 7.36%, reflecting the average monthly yields for 30-year treasury bonds plus 580 basis points. The reconciliation revenue requirement for 2020 provides for a weighted average debt and equity return on distribution rate base of 5.69%, inclusive of an allowed ROE of 7.29%, reflecting the average monthly yields for 30-year treasury bonds plus 580 basis points less a performance metrics penalty of 7 basis points. (b) The Joint Petition for Settlement was filed on September 15, 2021 and recommended for approval by the administrative law judge on October 6, 2021. PAPUC approval is expected in the fourth quarter of 2021. Transmission Formula Rates The Utility Registrants' transmission rates are each established based on a FERC-approved formula. ComEd, BGE, Pepco, DPL, and ACE are required to file an annual update to the FERC-approved formula on or before May 15, and PECO is required to file on or before May 31, with the resulting rates effective on June 1 of the same year. The annual update for ComEd is based on prior year actual costs and current year projected capital additions (initial year revenue requirement). The annual update for PECO is based on prior year actual costs and current year projected capital additions, accumulated depreciation, and accumulated deferred income taxes. The annual update for BGE, Pepco, DPL, and ACE is based on prior year actual costs and current year projected capital additions, accumulated depreciation, depreciation and amortization expense, and accumulated deferred income taxes. The update for ComEd also reconciles any differences between the revenue requirement in effect beginning June 1 of the prior year and actual costs incurred for that year (annual reconciliation). The update for PECO, BGE, Pepco, DPL, and ACE also reconciles any differences between the actual costs and actual revenues for the calendar year (annual reconciliation). For 2021, the following total increases/(decreases) were included in the Utility Registrants’ electric transmission formula rate updates: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Increase Total Revenue Requirement Increase (b) Allowed Return on Rate Base (c) Allowed ROE (d) ComEd $ 33 $ 12 $ 45 8.20 % 11.50 % PECO (2) 26 24 7.37 % 10.35 % BGE 38 27 65 7.35 % 10.50 % Pepco (9) 21 12 7.68 % 10.50 % DPL 19 33 52 7.20 % 10.50 % ACE 27 24 51 7.45 % 10.50 % __________ (a) All rates are effective June 1, 2021 - May 31, 2022, subject to review by interested parties pursuant to review protocols of each Utility Registrants' tariff. (b) In 2020, ComEd, BGE, Pepco, DPL, and ACE's transmission revenue requirement included a one-time decrease in accordance with the April 24, 2020 settlement agreement related to excess deferred income taxes which now completed has resulted in an increase to the 2021 transmission revenue requirement. In 2020, PECO's transmission revenue requirement included a one-time decrease in accordance with the December 5, 2019 settlement agreement related to refunds which now completed has resulted in an increase to the 2021 transmission revenue requirement. (c) Represents the weighted average debt and equity return on transmission rate bases. (d) As part of the FERC-approved settlements of ComEd’s 2007 and PECO's 2017 rate cases, the rate of return on common equity is 11.50% and 10.35%, respectively, inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55% and 55.75%, respectively. As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL, and ACE, the rate of return on common equity is 10.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO. Other State Regulatory Matters I llinois Regulatory Matters Clean Energy Law (Exelon and ComEd). On September 15, 2021, the Illinois Public Act 102-0662 was signed into law by the Governor of Illinois (“Clean Energy Law”). The Clean Energy Law includes, among other features, (1) procurement of carbon mitigation credits (CMCs) from qualifying nuclear-powered generating facilities, (2) a requirement to file a general rate case or a new four-year multi-year plan no later than January 20, 2023 to establish rates effective after ComEd’s existing performance-based distribution formula rate sunsets, (3) an extension of and certain adjustments to ComEd’s energy efficiency MWh savings goals, (4) revisions to the Illinois RPS requirements, including expanded charges for the procurement of RECs from wind and solar generation, (5) a requirement to accelerate amortization of ComEd’s unprotected excess deferred income taxes that ComEd was previously directed by the ICC to amortize using the average rate assumption method which equates to approximately 39.5 years, and (6) requirements that the ICC initiate and conduct various regulatory proceedings on subjects including ethics, spending, grid investments, and performance metrics. Regulatory or legal challenges regarding the validity or implementation of the Clean Energy Law are possible and Exelon, Generation, and ComEd cannot reasonably predict the outcome of any such challenges. Carbon Mitigation Credit The Clean Energy Law establishes decarbonization requirements for Illinois as well as programs to support the retention and development of emissions-free sources of electricity. Among other things, the Clean Energy Law authorizes the IPA to procure up to 54.5 million CMCs from qualifying nuclear plants for a five-year period beginning on June 1, 2022 through May 31, 2027. CMCs are credits for the carbon-free attributes of eligible nuclear power plants in PJM. The Byron, Dresden, and Braidwood nuclear plants located in Illinois will be eligible to participate in the CMC procurement process and, if awarded contracts, would be committed to operate through May 31, 2027. Selected generators will by December 3, 2021 contract directly with ComEd for the procurement of the CMCs based upon the number of MWhs produced annually by the eligible facilities, subject to specified caps and minimum performance requirements. The price to be paid for each CMC will be determined through a competitive bidding process that includes consumer-protection measures that cap the maximum acceptable bid amount and a formula that reduces CMC prices by an energy price index, the base residual auction capacity price in the ComEd zone of PJM, and the monetized value of any federal tax credit or other subsidy if applicable. The consumer protection measures contained in the new law will result in net payments to ComEd ratepayers if the energy index, the capacity price and applicable federal tax credits or subsidy exceed the maximum bid cap. ComEd is required to purchase CMCs from eligible nuclear facilities and all its costs of doing so will be recovered through a new rider. That rider will provide for an annual reconciliation and true-up to actual costs incurred by ComEd to purchase CMCs, with any difference to be credited to or collected from ComEd’s retail customers in subsequent periods. See Note 7 – Early Plant Retirements for the impacts of the provisions above on the Illinois nuclear plants and Generation’s consolidated financial statements. The provisions do not impact ComEd’s consolidated financial statements until 2022. ComEd Electric Distribution Rates The Clean Energy Law contains requirements associated with ComEd’s transition away from the performance-based electric distribution formula rate. The law authorizing that rate setting process sunsets at the end of 2022. The Clean Energy Law, and tariffs adopted under it, governs both the remaining reconciliations of rates set under that formula process and requires ComEd to file in 2023 its choice of either a general rate case or a four-year multi-year plan to set rates that take effect in 2024. If ComEd elects to file a multi-year plan, that plan would set rates for 2024 – 2027, based on forecasted revenue requirements and an ICC determined rate of return on rate base, including the cost of common equity. Each year of the multi-year plan is subject to after the fact ICC review and reconciliation of the plan’s revenue requirement for that year with the actual costs that the ICC determines are prudently and reasonably incurred for that year. That reconciliation is subject to adjustment for certain uncontrollable expenses and, unless the plan is modified, to a 5% cap on increases over the previously approved multi-year rate plan revenue requirement. ComEd would make its initial reconciliation filing in 2025, and the rate adjustments necessary to reconcile 2024 revenues to ComEd’s actual 2024 costs incurred would take effect in January 2026 after the ICC’s review. The ICC must also approve certain annual performance metrics, which can impose symmetrical performance adjustments in the total range of 20 to 60 basis points to ComEd’s rate of return on common equity based on the extent to which ComEd achieved the annual performance goals. ComEd will recover from retail customers, subject to certain exceptions, the costs it incurs pursuant to the Clean Energy Law either through its electric distribution rate or other recovery mechanisms. The Clean Energy Law, among other things, also requires ComEd’s rates to include a decoupling mechanism to eliminate any impacts of weather or load from ComEd’s electric distribution rate revenues. The Clean Energy Law also requires the ICC to initiate a docket to accelerate and fully credit to customers unprotected property related TCJA excess deferred income taxes no later than December 31, 2025. Energy Efficiency The Clean Energy Law extends ComEd’s current cumulative annual energy efficiency MWh savings goals through 2040, adds expanded electrification measures to those goals, increases low-income commitments and adds a new performance adjustment to the energy efficiency formula rate. ComEd expects its annual spend to increase in 2022 through 2040 to achieve these energy efficiency MWh savings goals, which will be deferred as a separate regulatory asset that will be recovered through the energy efficiency formula rate over the weighted average useful life, as approved by the ICC, of the related energy efficiency measures. Energy Efficiency Formula Rate (Exelon and ComEd). ComEd filed its annual energy efficiency formula rate update with the ICC on June 1, 2021. The filing establishes the revenue requirement used to set the rates that will take effect in January 2022 after the ICC’s review and approval. The requested revenue requirement update is based on a reconciliation of the 2020 actual costs plus projected 2022 expenditures. Initial Revenue Requirement Increase Annual Reconciliation Decrease Total Revenue Requirement Increase Requested Return on Rate Base (a) Requested ROE $ 55 $ (1) $ 54 5.72 % 7.36 % __________ (a) The requested revenue requirement increase provides for a weighted average debt and equity return on the energy efficiency regulatory asset and rate base of 5.72% inclusive of an allowed ROE of 7.36%, reflecting the monthly average yields for 30-year treasury bonds plus 580 basis points. For the 2020 reconciliation year, the requested revenue requirement provides for a weighted average debt and equity return on the energy efficiency regulatory asset and rate base of 6.26% inclusive of an allowed ROE of 8.46%, which includes an upward performance adjustment that increased the ROE. The performance adjustment can either increase or decrease the ROE based upon the achievement of energy efficiency savings goals. Maryland Regulatory Matters Maryland Order Directing the Distribution of Energy Assistance Funds (Exelon, BGE, PHI, Pepco, and DPL). On June 15, 2021, the MDPSC issued an order authorizing the disbursal of funds to utilities in accordance with Maryland COVID-19 relief legislation. Under this order, BGE, Pepco, and DPL received funds of $50 million, $12 million, and $8 million, respectively, in July 2021. The funds have been used to reduce or eliminate certain qualifying past-due residential customer receivables. New Jersey Regulatory Matters Conservation Incentive Program (CIP) (Exelon, PHI, and ACE). On September 25, 2020, ACE filed an application with the NJBPU as was required seeking approval to implement a portfolio of energy efficiency programs pursuant to New Jersey’s clean energy legislation. The filing included a request to implement a CIP that would eliminate the favorable and unfavorable impacts of weather and customer usage patterns on distribution revenues for most customers. The CIP compares current distribution revenues by customer class to approved target revenues established in ACE’s most recent distribution base rate case. The CIP is calculated annually and recovery is subject to certain conditions, including an earnings test and ceilings on customer rate increases. On April 27, 2021, the NJBPU approved the settlement filed by ACE and the third parties to the proceeding. The approved settlement addresses all material aspects of ACE’s filing, including ACE’s ability to implement the CIP prospectively effective July 1, 2021. As a result of this decoupling mechanism, operating revenues will no longer be impacted by abnormal weather or usage for most customers. Starting in third quarter of 2021, ACE will record alternative revenue program revenues for its best estimate of the distribution revenue impacts resulting from future changes in CIP rates that it believes are probable of approval by the NJBPU in accordance with this mechanism. Advanced Metering Infrastructure Filing (Exelon, PHI, and ACE). On August 26, 2020, ACE filed an application with the NJBPU as was required seeking approval to deploy a smart energy network in alignment with New Jersey’s Energy Master Plan and Clean Energy Act. The proposal consisted of estimated costs totaling $220 million with deployment taking place over a 3-year implementation period from approximately 2021 to 2024 that involves the installation of an integrated system of smart meters for all customers accompanied by the requisite communications facilities and data management systems. On July 14, 2021, the NJBPU approved the settlement filed by ACE and the third parties to the proceeding. The approved settlement addresses all material aspects of ACE's smart energy network deployment plan, including cost recovery of the investment costs, incremental O&M expenses, and the unrecovered balance of existing infrastructure through future distribution rates. Regulatory Assets and Liabilities The Utility Registrants' regulatory assets and liabilities have not changed materially since December 31, 2020, unless noted below. See Note 3 — Regulatory Matters of the Exelon 2020 Form 10-K for additional information on the specific regulatory assets and liabilities. ComEd . Regulatory assets increased $93 million primarily due to an increase of $47 million in the Electric Distribution Formula Rate Annual Reconciliations regulatory asset and $127 million in the Energy Efficiency Costs regulatory asset, partially offset by a decrease of $87 million in the renewable energy regulatory asset. PECO. Regulatory assets increased $135 million primarily due to an increase of $123 million in the Deferred Income Taxes regulatory asset and $14 million in the Vacation Accrual regulatory asset. Regulatory liabilities increased by $66 million primarily due to an increase of $71 million in the Nuclear Decommissioning regulatory liability partially offset by a $18 million decrease in the Electric Energy and Natural Gas Costs regulatory liability. BGE . Regulatory liabilities decreased $116 million primarily due to a decrease of $128 million in the Deferred Income Taxes regulatory liability offset by an increase of $12 million in Other regulatory liabilities. Pepco . Regulatory liabilities decreased $108 million primarily due to a decrease of $89 million in the Deferred Income Taxes regulatory liability and $19 million in the Transmission Formula Rate regulatory liability. DPL . Regulatory liabilities decreased $45 million primarily due to a decrease of $41 million in the Deferred Income Taxes regulatory liability. ACE . Regulatory liabilities decreased $61 million primarily due to a decrease of $67 million in the Deferred Income Taxes regulatory liability partially offset by an increase of $14 million in the Stranded Costs regulatory liability. Capitalized Ratemaking Amounts Not Recognized The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to the Utility Registrants' customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2021 $ 44 $ — $ — $ 39 $ 5 $ 3 $ 2 $ — December 31, 2020 51 (1) — 45 7 4 3 — __________ (a) Reflects ComEd's unrecognized equity returns/(losses) earned/(incurred) for ratemaking purposes on its electric distribution formula rate regulatory assets. (b) BGE's authorized amounts capitalized for ratemaking purposes primarily relate to earnings on shareholders' investment on its AMI programs. (c) Pepco's and DPL's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on their respective AMI Programs and Energy Efficiency and Demand Response Programs. The earnings on energy efficiency are on Pepco DC and DPL DE programs only. Generation Regulatory Matters (Exelon and Generation) Impacts of the February 2021 Extreme Cold Weather Event and Texas-based Generating Assets Outages Beginning on February 15, 2021, Generation’s Texas-based generating assets within the ERCOT market, specifically Colorado Bend II, Wolf Hollow II, and Handley, experienced outages as a result of extreme cold weather conditions. In addition, those weather conditions drove increased demand for service, dramatically increased wholesale power prices, and also increased gas prices in certain regions. In response to the high demand and significantly reduced total generation on the system, the PUCT directed ERCOT to use an administrative price cap of $9,000 per MWh during firm load shedding events. The estimated impact to Exelon’s and Generation’s Net income for the nine months ended September 30, 2021 arising from these market and weather conditions was a reduction of approximately $880 million. The estimated impact to Exelon's and Generation's Net income for the three months ended September 30, 2021 was not material. The ultimate impact to Exelon’s and Generation’s consolidated financial statements for the full year 2021 may be affected by a number of factors, including the impacts of customer and counterparty credit losses, any state or federal solutions to address the financial challenges caused by the event, and related litigation and contract disputes. During February and March 2021, various parties with differing interests, including generators and retail providers, filed requests with the PUCT to void the PUCT’s orders setting prices at $9,000 per MWh during firm load shedding events. Other requests were made for the PUCT to enforce its order and reduce prices for 33 hours between February 18 and February 19 after firm load shedding ceased, and to cap ancillary services at $9,000 per MWh. On March 2, 2021, a third party filed a notice of appeal in the Court of Appeals for the Third District of Texas challenging the validity of the PUCT’s actions. Generation intervened in that appeal and filed its initial brief on June 2, 2021. On April 19, 2021, Generation filed a declaratory action and request for judicial review of the PUCT’s orders setting prices at $9,000 per MWh in District Court of Travis County, Texas. Generation subsequently requested that the District Court of Travis County, Texas stay its proceeding pending action by the Court of Appeals in the third party proceeding. On May 17, 2021, Generation amended its petition for declaratory action and request for judicial review pending in the District Court of Travis County, Texas. Exelon and Generation cannot predict the outcome of these proceedings or the financial statement impact. Due to these events, a number of ERCOT market participants experienced bankruptcies or defaulted on payments to ERCOT, resulting in approximately a $3.0 billion payment shortfall in collections, which is allocated to the remaining ERCOT market participants. As of September 30, 2021, Generation has recorded its estimated portion of this obligation of approximately $17 million on a discounted basis, which is to be paid over a term of 83 years. ERCOT rules historically have limited recovery of default from market participants to $2.5 million per month market-wide. In February 2021, the PUCT gave ERCOT discretion to disregard those rules, but ERCOT has declined to exercise that discretion thus far. On March 8, 2021, a third party filed a notice of appeal in the Court of Appeals for the Third District of Texas challenging the validity of the PUCT's order to ERCOT in February 2021. Generation intervened in that appeal and filed its initial brief on July 7, 2021. On May 7, 2021, Generation filed a declaratory action and request for judicial review of the PUCT's order in the District Court of Travis County, Texas. Generation subsequently requested that the District Court of Travis County, Texas stay its proceeding pending action by the Court of Appeals in the third party proceeding. Exelon and Generation cannot predict the outcome of these proceedings or the financial statement impact. Additionally, several legislative proposals were introduced in the Texas legislature during February and March 2021 concerning the amount, timing and allocation of recovery of the $3.0 billion shortfall, as well as recovery of other costs associated with the PUCT's directive to set prices at $9,000 per MWh. Two of these proposals were enacted into law in June 2021 and establish financing mechanisms that ERCOT and certain market participants can utilize to fund amounts owed to ERCOT. Generation participated in proceedings before the PUCT addressing the proposed allocation of the $2.1 billion in securitized funds for reliability and ancillary service charges over $9,000/MWh. In September 2021, Generation entered into a settlement agreement and stipulation to resolve the allocation issues. The PUCT approved the settlement agreement and stipulation on October 13, 2021. In addition, other legislative proposals were introduced in the Texas legislature during February and March 2021 addressing cold-weather preparation for power plants and natural gas production and transportation infrastructure and the market structure for reliability services. The Texas legislature addressed these proposals by enacting a bill with a broad set of market reforms that, among other things, directed the PUCT to establish weatherization standards for electric generators within six months of enactment and gave the PUCT authority to impose administrative penalties if the new proposed standards, once adopted, are not met. On October 21, 2021, the PUCT adopted rule change requiring generators by December 1, 2021 to complete a number of specified winter readiness preparations and to submit to ERCOT a report describing and certifying the completion of those preparations. The PUCT described these requirements as the first phase of its actions with respect to winter preparedness, to be followed by a second phase consisting of a year-round set of weather preparedness standards to be informed by a weather study that is being conducted by ERCOT. The legislation also directs the PUCT to evaluate whether additional ancillary services are needed for reliability in the ERCOT power region to provide adequate incentives for dispatchable generation. Exelon and others have submitted various proposals to the PUCT with respect to a range of potential market reforms, including the implementation of additional ancillary service products as well as changes to the high system-wide offer cap and operating reserve demand curve, which remain pending. On September 23, 2021, the PUCT solicited comments regarding whether it should set ERCOT’s high system-wide offer cap at $4,500/MWh if the PUCT takes action to amend its rules with respect to that cap. Exelon and others submitted comments to the PUCT, which remain pending. The PUCT is expected to address potential changes to ERCOT’s market rules later in 2021. In February 2021, more than 70 local distribution companies (LDCs) and natural gas pipelines in multiple states throughout the mid-continent region, where Generation serves natural gas customers, issued operational flow orders (OFOs), curtailments or other limitations on natural gas transportation or use to manage the operational integrity of the applicable LDC or pipeline system. When in effect, gas transportation or use above these limitations is subject to significant penalties according to the applicable LDCs’ and natural gas pipelines’ tariffs. Gas transportation and supply in many states became restricted due to wells freezing and pipeline compression disruption, while demand was increasing due to the extreme cold temperatures, resulting in extremely high natural gas prices. Due to the extraordinary circumstances, many LDCs and natural gas pipelines have either voluntarily waived or have sought applicable regulatory approvals to waive the tariff penalties associated with the extreme weather event. During March 2021, three natural gas pipelines filed individual petitions with FERC requesting approval to waive OFO penalties. Generation also filed motions in March 2021 to intervene and filed comments in support of these FERC waiver requests. On March 25, 2021, FERC issued an order on one of the petitions approving a pipeline’s request for a limited waiver of penalties for February 15, 2021. On April 23, 2021, Generation and several other entities filed a request at FERC for rehearing of this order which was denied on May 24, 2021. Generation and the other entities filed an appeal of the rehearing of the order with the U.S. Court of Appeals for the D.C. Circuit on July 21, 2021. Additionally, Generation and the other entities filed a complaint requesting that FERC expand the order to include additional days of the weather event in February, from February 16 through February 19, 2021. On October 21, 2021, FERC denied the complaint finding that a pipeline has the discretion whether to waive penalties under its tariff. Generation is evaluating whether to seek rehearing and appeal of the FERC order. During April 2021, FERC issued orders on the remaining petitions approving the requests to waive the penalties. During May 2021, an LDC filed a motion with the Kansas Corporation Commission (KCC) requesting the KCC to grant a waiver from the tariff and allow the LDC to reduce the amounts assessed by permitting the removal of a multiplier from the penalty calculation. On October 8, 2021, a settlement was filed with the KCC that, if approved, would resolv

Revenue from Contracts with Cus

Revenue from Contracts with Customers (All Registrants)	9 Months Ended
Revenue from Contracts with Customers (All Registrants)	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers [Text Block]	Revenue from Contracts with Customers (All Registrants) The Registrants recognize revenue from contracts with customers to depict the transfer of goods or services to customers at an amount that the entities expect to be entitled to in exchange for those goods or services. Generation’s primary sources of revenue include competitive sales of power, natural gas, and other energy-related products and services. The Utility Registrants’ primary sources of revenue include regulated electric and gas tariff sales, distribution, and transmission services. See Note 4 — Revenue from Contracts with Customers of the Exelon 2020 Form 10-K for additional information regarding the primary sources of revenue for the Registrants. Contract Balances (All Registrants) Contract Assets Generation records contract assets for the revenue recognized on the construction and installation of energy efficiency assets and new power generating facilities before Generation has an unconditional right to bill for and receive the consideration from the customer. These contract assets are subsequently reclassified to receivables when the right to payment becomes unconditional. Generation records contract assets and contract receivables in Other current assets and Customer accounts receivable, net, respectively, in Exelon’s and Generation’s Consolidated Balance Sheets. The following table provides a rollforward of the contract assets reflected in Exelon's and Generation's Consolidated Balance Sheets for the three and nine months ended September 30, 2021 and 2020. The Utility Registrants do not have any contract assets. Exelon Generation Balance as of December 31, 2020 $ 144 $ 144 Amounts reclassified to receivables (16) (16) Revenues recognized 13 13 Amounts previously held-for-sale 12 12 Balance as of March 31, 2021 153 153 Amounts reclassified to receivables (12) (12) Revenues recognized 9 9 Balance as of June 30, 2021 150 150 Amounts reclassified to receivables (15) (15) Revenues recognized 14 14 Balance as of September 30, 2021 $ 149 $ 149 Exelon Generation Balance as of December 31, 2019 $ 174 $ 174 Amounts reclassified to receivables (19) (19) Revenues recognized 17 17 Balance as of March 31, 2020 172 172 Amounts reclassified to receivables (26) (26) Revenues recognized 13 13 Balance as of June 30, 2020 159 159 Amounts reclassified to receivables (18) (18) Revenues recognized 19 19 Balance as of September 30, 2020 $ 160 $ 160 Contract Liabilities The Registrants record contract liabilities when consideration is received or due prior to the satisfaction of the performance obligations. The Registrants record contract liabilities in Other current liabilities and Other noncurrent liabilities in the Registrants' Consolidated Balance Sheets. For Generation, these contract liabilities primarily relate to upfront consideration received or due for equipment service plans and the Illinois ZEC program that introduces a cap on the total consideration to be received by Generation. For PHI, Pepco, DPL, and ACE these contract liabilities primarily relate to upfront consideration received in the third quarter of 2020 for a collaborative arrangement with an unrelated owner and manager of communication infrastructure. The revenue attributable to this arrangement will be recognized as operating revenue over the 35 years under the collaborative arrangement. The following table provides a rollforward of the contract liabilities reflected in Exelon's, Generation's, PHI's, Pepco's, DPL's, and ACE's Consolidated Balance Sheets for the three and nine months ended September 30, 2021 and 2020. As of September 30, 2021 and December 31, 2020, ComEd's, PECO's, and BGE's contract liabilities were immaterial. Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2020 $ 151 $ 84 $ 118 $ 94 $ 12 $ 12 Consideration received or due 20 31 — — — — Revenues recognized (27) (64) (2) (2) — — Amounts previously held-for-sale 3 3 — — — — Balance as of March 31, 2021 147 54 116 92 12 12 Consideration received or due 17 39 — — — — Revenues recognized (32) (68) (3) (1) (1) (1) Balance as of June 30, 2021 132 25 113 91 11 11 Consideration received or due 31 93 — — — — Revenues recognized (26) (65) (2) (2) — — Balance as of September 30, 2021 $ 137 $ 53 $ 111 $ 89 $ 11 $ 11 Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2019 $ 33 $ 71 $ — $ — $ — $ — Consideration received or due 20 55 — — — — Revenues recognized (24) (70) — — — — Balance as of March 31, 2020 29 56 — — — — Consideration received or due 13 34 — — — — Revenues recognized (22) (63) — — — — Balance as of June 30, 2020 20 27 — — — — Consideration received or due 154 94 124 98 13 13 Revenues recognized (25) (65) (2) (2) — — Balance as of September 30, 2020 $ 149 $ 56 $ 122 $ 96 $ 13 $ 13 The following table reflects revenues recognized in the three and nine months ended September 30, 2021 and 2020, which were included in contract liabilities at December 31, 2020 and 2019, respectively: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Exelon $ 4 $ 2 $ 38 $ 25 Generation 2 2 81 63 PHI 2 — 7 — Pepco 2 — 5 — DPL — — 1 — ACE — — 1 — Transaction Price Allocated to Remaining Performance Obligations (All Registrants) The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 2021. This disclosure only includes contracts for which the total consideration is fixed and determinable at contract inception. The average contract term varies by customer type and commodity but ranges from one month to several years. This disclosure excludes Generation's power and gas sales contracts as they contain variable volumes and/or variable pricing. This disclosure also excludes the Utility Registrants' gas and electric tariff sales contracts and transmission revenue contracts as they generally have an original expected duration of one year or less and, therefore, do not contain any future, unsatisfied performance obligations to be included in this disclosure. 2021 2022 2023 2024 2025 and thereafter Total Exelon $ 82 $ 125 $ 50 $ 35 $ 184 $ 476 Generation 168 281 92 41 97 679 PHI 2 8 8 6 87 111 Pepco 2 6 6 5 70 89 DPL — 1 1 — 9 11 ACE — 1 1 1 8 11 Revenue Disaggregation (All Registrants) The Registrants disaggregate revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. See Note 5 — Segment Information for the presentation of the Registrant's revenue disaggregation.

Segment Information (All Regist

Segment Information (All Registrants)	9 Months Ended
Segment Information (All Registrants)	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Information (All Registrants)	Segment Information (All Registrants) Operating segments for each of the Registrants are determined based on information used by the CODM in deciding how to evaluate performance and allocate resources at each of the Registrants. Exelon has eleven reportable segments, which include Generation's five reportable segments consisting of the Mid-Atlantic, Midwest, New York, ERCOT, and all other power regions referred to collectively as “Other Power Regions” and ComEd, PECO, BGE, and PHI's three reportable segments consisting of Pepco, DPL, and ACE. ComEd, PECO, BGE, Pepco, DPL, and ACE each represent a single reportable segment, and as such, no separate segment information is provided for these Registrants. Exelon, ComEd, PECO, BGE, Pepco, DPL, and ACE's CODMs evaluate the performance of and allocate resources to ComEd, PECO, BGE, Pepco, DPL, and ACE based on net income. The basis for Generation's reportable segments is the integrated management of its electricity business that is located in different geographic regions, and largely representative of the footprints of ISO/RTO and/or NERC regions, which utilize multiple supply sources to provide electricity through various distribution channels (wholesale and retail). Generation's hedging strategies and risk metrics are also aligned to these same geographic regions. Descriptions of each of Generation’s five reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia, and parts of Pennsylvania and North Carolina. • Midwest represents operations in the western half of PJM and the United States footprint of MISO, excluding MISO’s Southern Region. • New York represents operations within NYISO. • ERCOT represents operations within Electric Reliability Council of Texas. • Other Power Regions: • New England represents the operations within ISO-NE. • South represents operations in the FRCC, MISO’s Southern Region, and the remaining portions of the SERC not included within MISO or PJM. • West represents operations in the WECC, which includes CAISO. • Canada represents operations across the entire country of Canada and includes AESO, OIESO, and the Canadian portion of MISO. The CODMs for Exelon and Generation evaluate the performance of Generation’s electric business activities and allocate resources based on Revenues Net of Purchased Power and Fuel Expense (RNF). Generation believes that RNF is a useful measurement of operational performance. RNF is not a presentation defined under GAAP and may not be comparable to other companies’ presentations or deemed more useful than the GAAP information provided elsewhere in this report. Generation’s operating revenues include all sales to third parties and affiliated sales to the Utility Registrants. Purchased power costs include all costs associated with the procurement and supply of electricity including capacity, energy, and ancillary services. Fuel expense includes the fuel costs for Generation’s owned generation and fuel costs associated with tolling agreements. The results of Generation's other business activities are not regularly reviewed by the CODM and are therefore not classified as operating segments or included in the regional reportable segment amounts. These activities include natural gas, as well as other miscellaneous business activities that are not significant to Generation's overall operating revenues or results of operations. Further, Generation’s unrealized mark-to-market gains and losses on economic hedging activities and its amortization of certain intangible assets and liabilities relating to commodity contracts recorded at fair value from mergers and acquisitions are also excluded from the regional reportable segment amounts. Exelon and Generation do not use a measure of total assets in making decisions regarding allocating resources to or assessing the performance of these reportable segments. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and nine months ended September 30, 2021 and 2020 is as follows: Three Months Ended September 30, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 4,330 $ — $ — $ — $ — $ — $ (319) $ 4,011 Competitive businesses natural gas revenues 575 — — — — — — 575 Competitive businesses other revenues (499) — — — — — (3) (502) Rate-regulated electric revenues — 1,789 762 677 1,444 — (15) 4,657 Rate-regulated natural gas revenues — — 56 93 23 — (3) 169 Shared service and other revenues — — — — 3 534 (537) — Total operating revenues $ 4,406 $ 1,789 $ 818 $ 770 $ 1,470 $ 534 $ (877) $ 8,910 2020 Competitive businesses electric revenues $ 4,201 $ — $ — $ — $ — $ — $ (326) $ 3,875 Competitive businesses natural gas revenues 323 — — — — — — 323 Competitive businesses other revenues 135 — — — — — (3) 132 Rate-regulated electric revenues — 1,643 759 646 1,339 — (22) 4,365 Rate-regulated natural gas revenues — — 54 85 23 — (3) 159 Shared service and other revenues — — — — 6 484 (491) (1) Total operating revenues $ 4,659 $ 1,643 $ 813 $ 731 $ 1,368 $ 484 $ (845) $ 8,853 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Intersegment revenues (c) : 2021 $ 324 $ 9 $ 2 $ 7 $ 3 $ 531 $ (876) $ — 2020 331 15 3 6 6 485 (845) 1 Depreciation and amortization: 2021 $ 866 $ 304 $ 86 $ 142 $ 210 $ 16 $ — $ 1,624 2020 558 294 85 133 200 19 — 1,289 Operating expenses: 2021 $ 3,465 $ 1,428 $ 677 $ 709 $ 1,155 $ 541 $ (858) $ 7,117 2020 4,727 1,302 658 642 1,102 489 (833) 8,087 Interest expense, net: 2021 $ 77 $ 98 $ 40 $ 36 $ 67 $ 79 $ — $ 397 2020 80 95 39 34 67 89 — 404 Income (loss) before income taxes: 2021 $ 814 $ 276 $ 108 $ 32 $ 264 $ (88) $ — $ 1,406 2020 219 256 122 61 215 (87) — 786 Income Taxes: 2021 $ 177 $ 56 $ (3) $ (4) $ (2) $ (50) $ — $ 174 2020 100 60 (16) 8 (1) 65 — 216 Net income (loss): 2021 $ 633 $ 220 $ 111 $ 36 $ 266 $ (37) $ — $ 1,229 2020 117 196 138 53 216 (151) — 569 Capital Expenditures: 2021 $ 367 $ 561 $ 301 $ 287 $ 410 $ 4 $ — $ 1,930 2020 282 554 312 290 386 9 — 1,833 (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. See Note 19— Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2021 Rate-regulated electric revenues $ 660 $ 337 $ 451 $ — $ (4) $ 1,444 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 92 (89) 3 Total operating revenues $ 660 $ 360 $ 451 $ 92 $ (93) $ 1,470 2020 Rate-regulated electric revenues $ 611 $ 314 $ 420 $ — $ (6) $ 1,339 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 91 (85) 6 Total operating revenues $ 611 $ 337 $ 420 $ 91 $ (91) $ 1,368 Intersegment revenues (c) : 2021 $ 2 $ 2 $ 1 $ 91 $ (93) $ 3 2020 3 3 1 90 (91) 6 Depreciation and amortization: 2021 $ 104 $ 53 $ 46 $ 7 $ — $ 210 2020 96 48 48 8 — 200 Operating expenses: 2021 $ 501 $ 295 $ 359 $ 93 $ (93) $ 1,155 2020 465 296 338 94 (91) 1,102 Interest expense, net: 2021 $ 35 $ 15 $ 14 $ 3 $ — $ 67 2020 35 15 15 2 — 67 Income (loss) before income taxes: 2021 $ 136 $ 53 $ 79 $ (4) $ — $ 264 2020 121 28 68 (2) — 215 Income Taxes: 2021 $ 6 $ 3 $ (11) $ — $ — $ (2) 2020 3 1 (7) 2 — (1) Net income (loss): 2021 $ 130 $ 50 $ 90 $ (4) $ — $ 266 2020 118 27 75 (4) — 216 Capital Expenditures: 2021 $ 202 $ 109 $ 97 $ 2 $ — $ 410 2020 188 94 103 1 — 386 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,145 $ 123 $ 1,268 $ 4 $ 1,272 Midwest 1,084 (99) 985 — 985 New York 445 10 455 — 455 ERCOT 191 165 356 2 358 Other Power Regions 948 318 1,266 (6) 1,260 Total Competitive Businesses Electric Revenues 3,813 517 4,330 — 4,330 Competitive Businesses Natural Gas Revenues 266 309 575 — 575 Competitive Businesses Other Revenues (c) 95 (594) (499) — (499) Total Generation Consolidated Operating Revenues $ 4,174 $ 232 $ 4,406 $ — $ 4,406 Three Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,327 $ (20) $ 1,307 $ 6 $ 1,313 Midwest 974 68 1,042 1 1,043 New York 401 5 406 — 406 ERCOT 249 74 323 7 330 Other Power Regions 937 186 1,123 (14) 1,109 Total Competitive Businesses Electric Revenues 3,888 313 4,201 — 4,201 Competitive Businesses Natural Gas Revenues 169 154 323 — 323 Competitive Businesses Other Revenues (c) 85 50 135 — 135 Total Generation Consolidated Operating Revenues $ 4,142 $ 517 $ 4,659 $ — $ 4,659 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $635 million and gains of $37 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 567 $ 3 $ 570 $ 586 $ 5 $ 591 Midwest 655 — 655 748 2 750 New York 343 3 346 281 4 285 ERCOT 181 (2) 179 141 6 147 Other Power Regions 233 (22) 211 253 (28) 225 Total RNF for Reportable Segments 1,979 (18) 1,961 2,009 (11) 1,998 Other (b) 881 18 899 336 11 347 Total Generation RNF $ 2,860 $ — $ 2,860 $ 2,345 $ — $ 2,345 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. includes: • unrealized mark-to-market gains of $754 million and gains of $255 million in 2021 and 2020, respectively; • accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 — Early Plant Retirements of $42 million and $24 million in 2021 and 2020 respectively; and • the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended September 30, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 978 $ 509 $ 383 $ 782 $ 309 $ 198 $ 275 Small commercial & industrial 433 113 73 150 36 53 61 Large commercial & industrial 148 67 128 320 244 27 49 Public authorities & electric railroads 11 7 7 15 8 4 3 Other (a) 245 61 104 172 53 56 63 Total rate-regulated electric revenues (b) $ 1,815 $ 757 $ 695 $ 1,439 $ 650 $ 338 $ 451 Rate-regulated natural gas revenues Residential $ — $ 36 $ 57 $ 10 $ — $ 10 $ — Small commercial & industrial — 13 10 5 — 5 — Large commercial & industrial — — 22 2 — 2 — Transportation — 5 — 3 — 3 — Other (c) — 2 6 3 — 3 — Total rate-regulated natural gas revenues (d) $ — $ 56 $ 95 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,815 $ 813 $ 790 $ 1,462 $ 650 $ 361 $ 451 Other revenues Revenues from alternative revenue programs $ (32) $ 3 $ (24) $ 6 $ 9 $ (2) $ — Other rate-regulated electric revenues (e) 6 2 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (26) $ 5 $ (20) $ 8 $ 10 $ (1) $ — Total rate-regulated revenues for reportable segments $ 1,789 $ 818 $ 770 $ 1,470 $ 660 $ 360 $ 451 Three Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 920 $ 518 $ 389 $ 763 $ 307 $ 193 $ 263 Small commercial & industrial 379 104 65 134 36 45 53 Large commercial & industrial 135 66 113 262 195 21 46 Public authorities & electric railroads 10 7 7 14 8 3 3 Other (a) 234 58 78 141 47 44 50 Total rate-regulated electric revenues (b) $ 1,678 $ 753 $ 652 $ 1,314 $ 593 $ 306 $ 415 Rate-regulated natural gas revenues Residential $ — $ 32 $ 55 $ 11 $ — $ 11 $ — Small commercial & industrial — 16 9 6 — 6 — Large commercial & industrial — — 21 1 — 1 — Transportation — 6 — 3 — 3 — Other (c) — 1 3 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 55 $ 88 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,678 $ 808 $ 740 $ 1,337 $ 593 $ 329 $ 415 Other revenues Revenues from alternative revenue programs $ (38) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Other rate-regulated electric revenues (e) 3 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ (35) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Total rate-regulated revenues for reportable segments $ 1,643 $ 813 $ 731 $ 1,368 $ 611 $ 337 $ 420 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $9 million, $15 million at ComEd • $2 million, $3 million at PECO • $4 million, $3 million at BGE • $3 million, $6 million at PHI • $2 million, $3 million at Pepco • $2 million, $3 million at DPL • $1 million, $1 million at ACE (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • less than $1 million at PECO both 2021 and 2020 • $3 million, $3 million at BGE (e) Includes late payment charge revenues. Nine Months Ended September 30, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 12,264 $ — $ — $ — $ — $ — $ (860) $ 11,404 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Competitive businesses natural gas revenues 2,408 — — — — — — 2,408 Competitive businesses other revenues (555) — — — — — (9) (564) Rate-regulated electric revenues — 4,840 2,033 1,866 3,726 — (33) 12,432 Rate-regulated natural gas revenues — — 366 560 118 — (9) 1,035 Shared service and other revenues — — — — 10 1,549 (1,559) — Total operating revenues $ 14,117 $ 4,840 $ 2,399 $ 2,426 $ 3,854 $ 1,549 $ (2,470) $ 26,715 2020 Competitive businesses electric revenues $ 11,367 $ — $ — $ — $ — $ — $ (920) $ 10,447 Competitive businesses natural gas revenues 1,348 — — — — — (3) 1,345 Competitive businesses other revenues 557 — — — — — (5) 552 Rate-regulated electric revenues — 4,499 1,948 1,763 3,425 — (50) 11,585 Rate-regulated natural gas revenues — — 358 521 116 — (5) 990 Shared service and other revenues — — — — 13 1,440 (1,447) 6 Total operating revenues $ 13,272 $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,440 $ (2,430) $ 24,925 Intersegment revenues (c) : 2021 $ 872 $ 19 $ 6 $ 20 $ 10 $ 1,542 $ (2,469) $ — 2020 932 31 7 16 13 1,435 (2,430) 4 Depreciation and amortization: 2021 $ 2,735 $ 893 $ 259 $ 434 $ 614 $ 52 $ 1 $ 4,988 2020 1,161 841 259 405 585 61 — 3,312 Operating expenses: 2021 $ 14,605 $ 3,833 $ 1,908 $ 2,080 $ 3,167 $ 1,572 $ (2,407) $ 24,758 2020 12,674 3,798 1,900 1,903 3,057 1,452 (2,397) 22,387 Interest expense, net: 2021 $ 225 $ 292 $ 119 $ 103 $ 201 $ 241 $ (1) $ 1,180 2020 277 287 108 99 201 269 — 1,241 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Income (loss) before income taxes: 2021 $ (8) $ 750 $ 392 $ 266 $ 538 $ (264) $ 1 $ 1,675 2020 532 446 310 299 340 (262) — 1,665 Income Taxes: 2021 $ 108 $ 141 $ 9 $ (24) $ 3 $ (8) $ — $ 229 2020 41 142 (7) 26 (77) 16 — 141 Net income (loss): 2021 $ (122) $ 609 $ 383 $ 290 $ 535 $ (255) $ 1 $ 1,441 2020 485 304 317 273 418 (278) — 1,519 Capital Expenditures: 2021 $ 1,086 $ 1,723 $ 878 $ 907 $ 1,299 $ 77 $ — $ 5,970 2020 1,212 1,583 824 838 1,072 77 — 5,606 Total assets: September 30, 2021 $ 48,010 $ 36,002 $ 13,733 $ 12,197 $ 24,502 $ 8,387 $ (10,210) $ 132,621 December 31, 2020 48,094 34,466 12,531 11,650 23,736 9,005 (10,165) 129,317 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. See Note 19 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2021 Rate-regulated electric revenues $ 1,736 $ 922 $ 1,080 $ — $ (12) $ 3,726 Rate-regulated natural gas revenues — 118 — — — 118 Shared service and other revenues — — — 281 (271) 10 Total operating revenues $ 1,736 $ 1,040 $ 1,080 $ 281 $ (283) $ 3,854 2020 Rate-regulated electric revenues $ 1,650 $ 838 $ 952 $ — $ (15) $ 3,425 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 279 (266) 13 Total operating revenues $ 1,650 $ 954 $ 952 $ 279 $ (281) $ 3,554 Intersegment revenues (c) : 2021 $ 4 $ 6 $ 2 $ 281 $ (283) $ 10 2020 6 7 3 278 (281) 13 Depreciation and amortization: 2021 $ 302 $ 157 $ 133 $ 22 $ — $ 614 2020 282 143 134 26 — 585 Operating expenses: 2021 $ 1,396 $ 858 $ 911 $ 285 $ (283) $ 3,167 2020 1,364 843 847 284 (281) 3,057 Interest expense, net: 2021 $ 104 $ 47 $ 43 $ 7 $ — $ 201 2020 103 47 45 6 — 201 Income (loss) before income taxes: 2021 $ 273 $ 144 $ 129 $ (8) $ — $ 538 2020 211 71 67 (9) — 340 Income Taxes: 2021 $ 9 $ 9 $ (12) $ (3) $ — $ 3 2020 (16) (20) (39) (2) — (77) Net income (loss): 2021 $ 264 $ 135 $ 141 $ (5) $ — $ 535 2020 227 91 106 (6) — 418 Capital Expenditures: 2021 $ 641 $ 320 $ 336 $ 2 $ — $ 1,299 2020 512 278 281 1 — 1,072 Total assets: September 30, 2021 $ 9,748 $ 5,295 $ 4,532 $ 4,977 $ (50) $ 24,502 December 31, 2020 9,264 5,140 4,286 5,079 (33) 23,736 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Nine Months Ended September 30, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,377 $ 134 $ 3,511 $ 16 $ 3,527 Midwest 3,067 (123) 2,944 1 2,945 New York 1,204 (30) 1,174 (1) 1,173 ERCOT 724 155 879 11 890 Other Power Regions 3,043 713 3,756 (27) 3,729 Total Competitive Businesses Electric Revenues 11,415 849 12,264 — 12,264 Competitive Businesses Natural Gas Revenues 1,384 1,024 2,408 — 2,408 Competitive Businesses Other Revenues (c) 291 (846) (555) — (555) Total Generation Consolidated Operating Revenues $ 13,090 $ 1,027 $ 14,117 $ — $ 14,117 Nine Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,692 $ (152) $ 3,540 $ 21 $ 3,561 Midwest 2,773 240 3,013 (6) 3,007 New York 1,074 (12) 1,062 (1) 1,061 ERCOT 579 155 734 20 754 Other Power Regions 2,718 300 3,018 (34) 2,984 Total Competitive Businesses Electric Revenues 10,836 531 11,367 — 11,367 Competitive Businesses Natural Gas Revenues 881 467 1,348 — 1,348 Competitive Businesses Other Revenues (c) 268 289 557 — 557 Total Generation Consolidated Operating Revenues $ 11,985 $ 1,287 $ 13,272 $ — $ 13,272 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $958 million and gains of $238 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 1,698 $ 14 $ 1,712 $ 1,660 $ 23 $ 1,683 Midwest 2,014 1 2,015 2,180 (2) 2,178 New York 873 7 880 714 11 725 ERCOT (775) (147) (922) 311 14 325 Other Power Regions 641 (77) 564 608 (70) 538 Total RNF for Reportable Segments 4,451 (202) 4,249 5,473 (24) 5,449 Other (b) 1,563 202 1,765 838 24 862 Total Generation RNF $ 6,014 $ — $ 6,014 $ 6,311 $ — $ 6,311 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Primarily includes: • unrealized mark-to-market gains of $1,242 million and gains of $472 million in 2021 and 2020, respectively; • accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 — Early Plant Retirements of $148 million and $24 million in 2021 and 2020 respectively; and • the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,479 $ 1,325 $ 1,044 $ 1,924 $ 785 $ 535 $ 604 Small commercial & industrial 1,176 312 202 392 101 145 146 Large commercial & industrial 420 183 342 825 616 70 139 Public authorities & electric railroads 33 24 20 45 24 11 10 Other (a) 676 167 269 453 154 143 158 Total rate-regulated electric revenues (b) $ 4,784 $ 2,011 $ 1,877 $ 3,639 $ 1,680 $ 904 $ 1,057 Rate-regulated natural gas revenues Residential $ — $ 251 $ 354 $ 67 $ — $ 67 $ — Small commercial & industrial — 94 59 29 — 29 — Large commercial & industrial — — 103 5 — 5 — Transportation — 17 — 11 — 11 — Other (c) — 4 41 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 366 $ 557 $ 118 $ — $ 118 $ — Total rate-regulated revenues from contracts with customers $ 4,784 $ 2,377 $ 2,434 $ 3,757 $ 1,680 $ 1,022 $ 1,057 Other revenues Revenues from alternative revenue programs $ 32 $ 20 $ (17) $ 94 $ 54 $ 17 $ 23 Other rate-regulated electric revenues (e) 24 2 7 3 2 1 — Other rate-regulated natural gas revenues (e) — — 2 — — — — Total other revenues $ 56 $ 22 $ (8) $ 97 $ 56 $ 18 $ 23 Total rate-regulated revenues for reportable segments $ 4,840 $ 2,399 $ 2,426 $ 3,854 $ 1,736 $ 1,040 $ 1,080 Nine Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,389 $ 1,277 $ 1,034 $ 1,825 $ 779 $ 501 $ 545 Small commercial & industrial 1,067 291 183 355 101 127 127 Large commercial & industrial 388 174 311 755 558 66 131 Public authorities & electric railroads 33 21 20 45 25 10 10 Other (a) 663 171 233 471 166 148 159 Total rate-regulated electric revenues (b) $ 4,540 $ 1,934 $ 1,781 $ 3,451 $ 1,629 $ 852 $ 972 Rate-regulated natural gas revenues Residential $ — $ 252 $ 342 $ 68 $ — $ 68 $ — Small commercial & industrial — 86 55 30 — 30 — Large commercial & industrial — — 96 3 — 3 — Transportation — 18 — 10 — 10 — Other (c) — 3 16 5 — 5 — Total rate-regulated natural gas revenues (d) $ — $ 359 $ 509 $ 116 $ — $ 116 $ — Total rate-regulated revenues from contracts with customers $ 4,540 $ 2,293 $ 2,290 $ 3,567 $ 1,629 $ 968 $ 972 Other revenues Revenues from alternative revenue programs $ (51) $ 10 $ (10) $ (15) $ 20 $ (15) $ (20) Other rate-regulated electric revenues (e) 10 3 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (41) $ 13 $ (6) $ (13) $ 21 $ (14) $ (20) Total rate-regulated revenues for reportable segments $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,650 $ 954 $ 952 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $19 million, $31 million at ComEd • $5 million, $6 million at PECO • $10 million, $9 million at BGE • $10 million, $13 million at PHI • $4 million, $6 million at Pepco • $6 million, $7 million at DPL • $2 million, $3 million at ACE (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $1 million, $1 million at PECO • $10 million, $7 million at BGE (e) Includes late payment charge revenues.

Accounts Receivable (All Regist

Accounts Receivable (All Registrants)	9 Months Ended
Accounts Receivable (All Registrants)	Sep. 30, 2021
Credit Loss [Abstract]
Accounts Receivable (All Registrants) [Text Block]	Accounts Receivable (All Registrants) Allowance for Credit Losses on Accounts Receivable (All Registrants) The following tables present the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2021 $ 395 $ 75 $ 89 $ 111 $ 27 $ 93 $ 38 $ 19 $ 36 Plus: Current period provision for expected credit losses (a) 47 10 11 1 7 18 5 3 10 Less: Write-offs, net of recoveries (b) 33 1 12 11 3 6 2 4 — Balance as of September 30, 2021 $ 409 $ 84 $ 88 $ 101 $ 31 $ 105 $ 41 $ 18 $ 46 Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 261 $ 33 $ 72 $ 71 $ 23 $ 62 $ 24 $ 18 $ 20 Plus: Current period provision for expected credit losses (c) 114 1 37 27 14 35 11 7 17 Less: Write-offs, net of recoveries (b) 17 1 4 2 2 8 — 3 5 Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2020 $ 366 $ 32 $ 97 $ 116 $ 35 $ 86 $ 32 $ 22 $ 32 Plus: Current period provision for expected credit losses (d) 122 57 23 7 2 33 15 4 14 Less: Write-offs, net of recoveries (b) 79 5 32 22 6 14 6 8 — Balance as of September 30, 2021 $ 409 $ 84 $ 88 $ 101 $ 31 $ 105 $ 41 $ 18 $ 46 Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 243 $ 80 $ 59 $ 55 $ 12 $ 37 $ 13 $ 11 $ 13 Plus: Current period provision for expected credit losses (c) 222 13 62 56 28 63 24 14 25 Less: Write-offs, net of recoveries (b) 51 4 16 15 5 11 2 3 6 Less: Sale of customer accounts receivable (e) 56 56 — — — — — — — Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 __________ (a) For ACE, the increase is primarily a result of increased aging of receivables and a slight decrease in the expected recovery rate. (b) Recoveries were not material to the Registrants. (c) For the Utility Registrants, the increase is primarily as a result of increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnections of service to customers previously disconnected due to COVID-19. (d) For Generation, primarily relates to the impacts of the February 2021 extreme cold weather event. See Note 3 — Regulatory Matters for additional information. For PHI, Pepco, and ACE, the increase is primarily a result of increased aging of receivables and a slight decrease in the expected recovery rate. (e) See below for additional information on the sale of customer accounts receivable at Generation in the second quarter of 2020. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2021 $ 72 $ 1 $ 18 $ 7 $ 8 $ 38 $ 16 $ 9 $ 13 Plus: Current period provision for expected credit losses 9 3 2 1 1 2 1 (1) 2 Less: Write-offs, net of recoveries (a) 4 — 1 1 1 — — — — Balance as of September 30, 2021 $ 77 $ 4 $ 19 $ 7 $ 8 $ 40 $ 17 $ 8 $ 15 Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 61 $ — $ 22 $ 7 $ 6 $ 26 $ 11 $ 7 $ 8 Plus: Current period provision for expected credit losses 15 — 5 1 3 6 2 1 3 Less: Write-offs, net of recoveries (a) 1 — — 1 — — — — — Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2020 $ 71 $ — $ 21 $ 8 $ 9 $ 33 $ 13 $ 9 $ 11 Plus: Current period provision for expected credit losses 15 4 — 2 2 7 4 (1) 4 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 — — — — Balance as of September 30, 2021 $ 77 $ 4 $ 19 $ 7 $ 8 $ 40 $ 17 $ 8 $ 15 Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 48 $ — $ 20 $ 7 $ 5 $ 16 $ 7 $ 4 $ 5 Plus: Current period provision for expected credit losses 36 — 9 3 7 17 6 4 7 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 1 — — 1 Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 __________ (a) Recoveries were not material to the Registrants. Unbilled Customer Revenue (All Registrants) The following table provides additional information about unbilled customer revenues recorded in the Registrants' Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 $ 941 $ 359 $ 224 $ 113 $ 98 $ 147 $ 70 $ 34 $ 43 December 31, 2020 998 258 218 147 197 178 87 62 29 __________ (a) Unbilled customer revenues are classified in Customer accounts receivables, net in the Registrants' Consolidated Balance Sheets. Sales of Customer Accounts Receivable (Exelon and Generation) On April 8, 2020, NER, a bankruptcy remote, special purpose entity, which is wholly-owned by Generation, entered into a revolving accounts receivable financing arrangement with a number of financial institutions and a commercial paper conduit (the Purchasers) to sell certain customer accounts receivable (the Facility). The Facility had a maximum funding limit o f $750 million and was scheduled to expire on April 7, 2021, unless renewed by the mutual consent of the parties in accordance with its terms. The Facility was renewed on March 29, 2021. The Facility term was extended through March 29, 2024, unless further renewed by the mutual consent of the parties, and the maximum funding limit was increased to $900 million. Un der the Facility, NER may sell eligible short-term customer accounts receivable to the Purchasers in exchange for cash and subordinated interest. The transfers are reported as sales of receivables in Exelon’s and Generation’s consolidated financial statements. The subordinated interest in collections upon the receivables sold to the Purchasers is referred to as the DPP, which is reflected in Other current assets in Exelon’s and Generation’s Consolidated Balance Sheets. The Facility requires the balance of eligible receivables to be maintained at or above the balance of cash proceeds received from the Purchasers. To the extent the eligible receivables decrease below such balance, Generation is required to repay cash to the Purchasers. When eligible receivables exceed cash proceeds, Generation has the ability to increase the cash received up to the maximum funding limit. These cash inflows and outflows impact the DPP. On April 8, 2020, Generation derecognized and transferred approximatel y $1.2 billion of receivables at fair value to the Purchasers in exchange for approximately $500 million in cash purchase price and $650 million of DP P. During the first quarter of 2021, Generation received additional c ash of $250 million from the Purchasers for the remaining available funding in the Facility. Additionally, during the first quarter of 2021, Generation received cash of approxi mately $150 million from the Purchasers in connection with the increased funding limit at the time of the Facility renewal. During the second quarter of 2021, Generation returned cash of $50 million to the Purchasers due to the eligible receivables decreasing temporarily. Subsequently, in the second quarter, Generation received cash of $50 million from the Purchasers as a result of an increase in the eligible receivable balance. The $50 million cash outflow and inflow is included in the Collection of DPP line within Cash flows from investing activities in Exelon’s and Generation’s Consolidated Statements of Cash Flows. The following table summarizes the impact of the sale of certain receivables: September 30, 2021 December 31, 2020 Derecognized receivables transferred at fair value $ 1,401 $ 1,139 Cash proceeds received 900 500 DPP 501 639 Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Loss on sale of receivables (a) $ 1 $ 8 $ 26 $ 23 __________ (a) Reflected in Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Nine Months Ended September 30, 2021 2020 Proceeds from new transfers (a) $ 4,440 $ 1,889 Cash collections received on DPP and reinvested in the Facility (b) 2,652 2,518 Cash collections reinvested in the Facility 7,092 4,407 __________ (a) Customer accounts receivable sold into the Facility were $7,373 million and $4,515 million for the nine months ended September 30, 2021 and September 30, 2020, respectively. (b) Does not include the $400 million in cash proceeds received from the Purchasers in the first quarter of 2021. Generation’s risk of loss following the transfer of accounts receivable is limited to the DPP outstanding. Payment of DPP is not subject to significant risks other than delinquencies and credit losses on accounts receivable transferred, which have historically been and are expected to be immaterial. Generation continues to service the receivables sold in exchange for a servicing fee. Generation did not record a servicing asset or liability as the servicing fees were immaterial. Generation recognizes the cash proceeds received upon sale in Net cash provided by operating activities in the Consolidated Statements of Cash Flows. The collection and reinvestment of DPP is recognized in Net cash provided by investing activities in the Consolidated Statements of Cash Flows. See Note 14 — Fair Value of Financial Assets and Liabilities and Note 17 — Variable Interest Entities for additional information. Other Purchases and Sales of Customer and Other Accounts Receivables (All Registrants) Generation is required, under supplier tariffs in ISO-NE, MISO, NYISO, and PJM, to sell customer and other receivables to utility companies, which include the Utility Registrants. The Utility Registrants are required, under separate legislation and regulations in Illinois, Pennsylvania, Maryland, District of Columbia, Delaware, and New Jersey, to purchase certain receivables from alternative retail electric and, as applicable, natural gas suppliers that participate in the utilities' consolidated billing. The following tables present the total receivables purchased and sold. Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 2,945 $ — $ 810 $ 795 $ 531 $ 826 $ 504 $ 166 $ 156 Total receivables sold 100 117 — — — — — — — Related party transactions: Receivables purchased from Generation — — — — 17 — — — — Receivables sold to the Utility Registrants — 17 — — — — — — — Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 2,698 $ — $ 865 $ 786 $ 508 $ 787 $ 484 $ 160 $ 143 Total receivables sold 542 790 — — — — — — — Related party transactions: Receivables purchased from Generation — — 34 67 75 72 51 13 8 Receivables sold to the Utility Registrants — 248 — — — — — — —

Early Plant Retirements (Exelon

Early Plant Retirements (Exelon and Generation)	9 Months Ended
Early Plant Retirements (Exelon and Generation)	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Early Plant Retirements (Exelon and Generation)	Early Plant Retirements (Exelon and Generation) Exelon and Generation continuously evaluate factors that affect the current and expected economic value of Generation’s plants, including, but not limited to: market power prices, results of capacity auctions, potential legislative and regulatory solutions to ensure plants are fairly compensated for benefits they provide through their carbon-free emissions, reliability, or fuel security, and the impact of potential rules from the EPA requiring reduction of carbon and other emissions and the efforts of states to implement those final rules. The precise timing of an early retirement date for any plant, and the resulting financial statement impacts, may be affected by many factors, including the status of potential regulatory or legislative solutions, results of any transmission system reliability study assessments, the nature of any co-owner requirements and stipulations, and NDT fund requirements for nuclear plants, among other factors. However, the earliest retirement date for any plant would usually be the first year in which the unit does not have capacity or other obligations, and where applicable, just prior to its next scheduled nuclear refueling outage. Nuclear Generation On August 27, 2020, Generation announced that it intended to permanently cease generation operations at Byron in September 2021 and at Dresden in November 2021. Neither of these nuclear plants cleared in PJM’s capacity auction for the 2022-2023 planning year held in May 2021. Generation’s Braidwood and LaSalle nuclear plants in Illinois did clear in the capacity auction, but were also showing increased signs of economic distress. On September 15, 2021, the Illinois Public Act 102-0662 was signed into law by the Governor of Illinois (“Clean Energy Law”). The Clean Energy Law is designed to achieve 100% carbon-free power by 2045 to enable the state’s transition to a clean energy economy. Among other things, the Clean Energy Law authorizes the IPA to procure up to 54.5 million CMCs from qualifying nuclear plants for a five-year period beginning on June 1, 2022 through May 31, 2027. CMCs are credits for the carbon-free attributes of eligible nuclear power plants in PJM. The Byron, Dresden, and Braidwood nuclear plants located in Illinois will be eligible to participate in the CMC procurement process and, if awarded contracts, would be committed to operate through May 31, 2027. See Note 3 — Regulatory Matters for additional information. Following enactment of the legislation, Generation announced on September 15, 2021, that it has reversed its previous decision to retire Byron and Dresden given the opportunity for additional revenue under the Clean Energy Law. In addition, Generation no longer considers the Braidwood or LaSalle nuclear plants to be at risk for premature retirement. As a result of the decision to early retire Byron and Dresden, Exelon and Generation recognized certain one-time charges in the third and fourth quarters of 2020 related to materials and supplies inventory reserve adjustments, employee-related costs including severance benefit costs, and construction work-in-progress impairments, among other items. In addition, there were ongoing annual financial impacts stemming from shortening the expected economic useful lives of these nuclear plants primarily related to accelerated depreciation of plant assets (including any ARC), accelerated amortization of nuclear fuel, and changes in ARO accretion expense associated with the changes in decommissioning timing and cost assumptions to reflect an earlier retirement date. In the third quarter of 2021, Exelon and Generation reversed $81 million of severance benefit costs and $13 million of other one-time charges initially recorded in Operating and maintenance expense in the third and fourth quarters of 2020 associated with the early retirements. In addition, Generation updated the expected economic useful life for both facilities to 2044 and 2046 for Byron Units 1 and 2, respectively, and to 2029 and 2031 for Dresden Units 2 and 3, respectively, the end of the respective NRC operating license for each unit. Depreciation was therefore adjusted beginning September 15, 2021, to reflect these extended useful life estimates. See Note 8 — Nuclear Decommissioning for additional detail on changes to the nuclear decommissioning ARO balances resulting from the initial decision and subsequent reversal of the decision to early retire Byron and Dresden. The total impact for the three and nine months ended September 30, 2021 and 2020 in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income resulting from the initial decision and subsequent reversal of the decision to early retire Byron and Dresden is summarized in the table below. Income statement expense (pre-tax) Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Three and Nine Months Ended September 30, 2020 Depreciation and amortization Accelerated depreciation (a) $ 574 $ 1,805 $ 254 Accelerated nuclear fuel amortization 42 148 14 Operating and maintenance One-time charges (94) (94) 220 Other charges 4 8 34 Contractual offset (b) (60) (451) (129) Total $ 466 $ 1,416 $ 393 _________ (a) Includes the accelerated depreciation of plant assets including any ARC. (b) Reflects contractual offset for ARO accretion and ARC depreciation and excludes any changes in earnings in the NDT funds. Decommissioning-related impacts were not offset for the Byron units starting in the second quarter of 2021 due to the inability to recognize a regulatory asset at ComEd. With Generation’s September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. Based on the regulatory agreement with the ICC, decommissioning-related activities are offset in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income as long as the net cumulative decommissioning-related activities result in a regulatory liability at ComEd. The offset resulted in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 8 — Nuclear Decommissioning for additional information. Generation remains committed to continued operations for its other nuclear plants receiving state-supported payments under the Illinois ZES (Clinton and Quad Cities), New Jersey ZEC program (Salem), and the New York CES (FitzPatrick, Ginna, and Nine Mile Point) assuming the continued effectiveness of such programs. To the extent such programs do not operate as expected over their full terms, each of these plants would be at heightened risk for early retirement, which could have a material impact on Exelon’s and Generation’s future financial statements. See Note 3 — Regulatory Matters for additional information on the New Jersey ZEC program and Note 3 — Regulatory Matters of the 2020 Form 10-K for additional information on the Illinois ZES and New York CES. Exelon continues to work with stakeholders on state policy solutions to support continued operation of our nuclear fleet, while also advocating for broader market reforms at the regional and federal level. The absence of such solutions or reforms could have a material unfavorable impact on Exelon's and Generation's future results of operations. Other Generation In March 2018, Generation notified ISO-NE of its plans to early retire, among other assets, the Mystic Generating Station's units 8 and 9 (Mystic 8 and 9) absent regulatory reforms to properly value reliability and regional fuel security. Thereafter, ISO-NE identified Mystic 8 and 9 as being needed to ensure fuel security for the region and entered into a cost of service agreement with these two units for the period between June 1, 2022 - May 31, 2024. The agreement was approved by FERC in December 2018. On June 10, 2020, Generation filed a complaint with FERC against ISO-NE stating that ISO-NE failed to follow its tariff with respect to its evaluation of Mystic 8 and 9 for transmission security for the 2024 to 2025 Capacity Commitment Period and that the modifications that ISO-NE made to its unfiled planning procedures to avoid retaining Mystic 8 and 9 should have been filed with FERC for approval. On August 17, 2020, FERC issued an order denying the complaint. As a result, on August 20, 2020, Exelon determined that Generation will permanently cease generation operations at Mystic 8 and 9 at the expiration of the cost of service commitment in May 2024. See Note 3 — Regulatory Matters for additional discussion of Mystic’s cost of service agreement. As a result of the decision to early retire Mystic 8 and 9, Exelon and Generation recognized $43 million in the third quarter of 2020 of one-time charges related to an expected long-term contract termination and materials and supplies reserve adjustments, among other items. In addition, there are financial impacts stemming from shortening the expected economic useful life of Mystic 8 and 9 primarily related to accelerated depreciation of plant assets. Exelon and Generation recorded an immaterial amount of incremental Depreciation and amortization expense for the three months ended September 30, 2021 and $41 million for the nine months ended September 30, 2021. Exelon and Generation recorded incremental Depreciation and amortization expense of $6 million for the three and nine months ended September 30, 2020.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	9 Months Ended
Nuclear Decommissioning (Exelon and Generation)	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Nuclear Decommissioning (Exelon and Generation)	Nuclear Decommissioning (Exelon and Generation) Nuclear Decommissioning Asset Retirement Obligations Generation has a legal obligation to decommission its nuclear power plants following the expiration of their operating licenses. To estimate its decommissioning obligation related to its nuclear generating stations for financial accounting and reporting purposes, Generation uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimates and assumptions, and are based on decommissioning cost studies, cost escalation rates, probabilistic cash flow models, and discount rates. Generation updates its ARO annually, unless circumstances warrant more frequent updates, based on its review of updated cost studies and its annual evaluation of cost escalation factors and probabilities assigned to various scenarios. The financial statement impact for changes in the ARO, on an individual unit basis, due to the changes in and timing of estimated cash flows generally result in a corresponding change in the unit’s ARC in Property, plant, and equipment in Exelon’s and Generation’s Consolidated Balance Sheets. If the ARO decreases for a Non-Regulatory Agreement unit without any remaining ARC, the corresponding change is recorded as decrease in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The following table provides a rollforward of the nuclear decommissioning ARO reflected in Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2020 to September 30, 2021: Nuclear decommissioning ARO at December 31, 2020 (a) $ 11,922 Accretion expense 375 Net increase due to changes in, and timing of, estimated future cash flows 256 Costs incurred related to decommissioning plants (57) Nuclear decommissioning ARO at September 30, 2021 (a) $ 12,496 _________ (a) Includes $74 million and $80 million as the current portion of the ARO at September 30, 2021 and December 31, 2020, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. During the nine months ended September 30, 2021, the net $256 million increase in the ARO for the changes in the amounts and timing of estimated decommissioning cash flows was driven by multiple adjustments. These adjustments primarily include: • An increase of approximately $510 million for updated cost escalation rates, primarily for labor and energy, and a decrease in discount rates. • A net decrease of approximately $170 million was driven by updates to Byron and Dresden reflecting changes in assumed retirement dates and assumed methods of decommissioning as a result of the reversal of the decision to early retire the plants. See Note 7 — Early Plant Retirements for additional information. • A net decrease of approximately $110 million due to lower estimated costs to decommission Byron, Braidwood, Dresden, LaSalle, and Zion nuclear units resulting from the completion of updated cost studies. The 2021 ARO updates resulted in a decrease of $51 million in Operating and maintenance expense for the three and nine months ended September 30, 2021 in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. NDT Funds Exelon and Generation had NDT funds totaling $15,602 million and $14,599 million at September 30, 2021 and December 31, 2020, respectively. The NDT funds also include $198 million and $134 million for the current portion of the NDT funds at September 30, 2021 and December 31, 2020, respectively, which are included in Other current assets in Exelon's and Generation's Consolidated Balance Sheets. See Note 18 — Supplemental Financial Information for additional information on activities of the NDT funds. Accounting Implications of the Regulatory Agreements with ComEd and PECO Based on the regulatory agreements with the ICC and PAPUC that dictate Generation’s obligations related to the shortfall or excess of NDT funds necessary for decommissioning the former ComEd units on a unit-by-unit basis and the former PECO units in total, decommissioning-related activities net of applicable taxes, including realized and unrealized gains and losses on the NDT funds, depreciation of the ARC, and accretion of the decommissioning obligation, are generally offset in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income and are recorded by Generation and the corresponding regulated utility as a component of the intercompany and regulatory balances in the balance sheet. For the purposes of making this determination, the decommissioning obligation referred to is different from the calculation used in the NRC minimum funding obligation filings based on NRC guidelines. For the former ComEd units, given no further recovery from ComEd customers is permitted and Generation retains an obligation to ultimately return any unused NDTs to ComEd customers (on a unit-by-unit basis), to the extent the related NDT investment balances are expected to exceed the total estimated decommissioning obligation for each unit, decommissioning-related activities are offset in the Consolidated Statements of Operations and Comprehensive Income which results with Generation recognizing an intercompany payable to ComEd while ComEd records an intercompany receivable from Generation with a corresponding regulatory liability. However, given the asymmetric settlement provision that does not allow for continued recovery from ComEd customers in the event of a shortfall, recognition of a regulatory asset at ComEd is not permissible and accounting for decommissioning-related activities at Generation for that unit would not be offset, and the impact to Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income could be material during such periods. During the second and third quarter of 2021, a pre-tax charge of $53 million and $140 million , respectively, was recorded in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income for decommissioning-related activities that were not offset for the Byron units due to contractual offset being temporarily suspended. With Generation’s September 15, 2021 reversal of the previous decision to retire Byron and the corresponding adjustment to the ARO for Byron discussed previously, Generation resumed contractual offset for Byron as of that date. As of September 30, 2021, decommissioning-related activities for all of the former ComEd units, except for Zion, are currently offset in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The decommissioning-related activities related to the Non-Regulatory Agreement Units are reflected in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information. NRC Minimum Funding Requirements NRC regulations require that licensees of nuclear generating facilities demonstrate reasonable assurance that funds will be available in specified minimum amounts to decommission the facility at the end of its life. Generation filed its biennial decommissioning funding status report with the NRC on February 24, 2021 for all units, including its shutdown units, except for Zion Station which is included in a separate report to the NRC submitted by ZionSolutions, LLC. The status report demonstrated adequate decommissioning funding assurance as of December 31, 2020 for all units except for Byron Units 1 and 2. Generation filed an updated decommissioning funding status report for Byron Units 1 and 2 and Dresden Units 2 and 3 on September 28, 2021 based on their current license expiration dates consistent with Generation’s announcements regarding the continued operations of these units. This report demonstrated adequate decommissioning funding assurance as of December 31, 2020 for Byron Units 1 and 2 and Dresden Units 2 and 3. Generation will file its next decommissioning funding status report with the NRC by March 31, 2022. This report will reflect the status of decommissioning funding assurance as of December 31, 2021 for shutdown units.

Asset Impairments (Exelon and G

Asset Impairments (Exelon and Generation)	9 Months Ended
Asset Impairments (Exelon and Generation)	Sep. 30, 2021
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Asset Impairments (Exelon and Generation)	Asset Impairments (Exelon and Generation)The Registrants evaluate the carrying value of long-lived assets or asset groups for recoverability whenever events or changes in circumstances indicate that the carrying value of those assets may not be recoverable. Indicators of impairment may include a deteriorating business climate, including, but not limited to, declines in energy prices, condition of the asset, specific regulatory disallowance, or plans to dispose of a long-lived asset significantly before the end of its useful life. The Registrants determine if long-lived assets or asset groups are impaired by comparing the undiscounted expected future cash flows to the carrying value. When the undiscounted cash flow analysis indicates a long-lived asset or asset group is not recoverable, the amount of the impairment loss is determined by measuring the excess of the carrying amount of the long-lived asset or asset group over its fair value. The fair value analysis is primarily based on the income approach using significant unobservable inputs (Level 3) including revenue and generation forecasts, projected capital and maintenance expenditures, and discount rates. A variation in the assumptions used could lead to a different conclusion regarding the recoverability of an asset or asset group and, thus, could potentially result in material future impairments of the Registrant's long-lived assets. New England Asset Group In the third quarter of 2020, in conjunction with the retirement announcement of Mystic Units 8 and 9, Generation completed a comprehensive review of the estimated undiscounted future cash flows of the New England asset group and concluded that the estimated undiscounted future cash flows and fair value of the New England asset group were less than their carrying values. As a result, a pre-tax impairment charge of $500 million was recorded in the third quarter of 2020 in Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. See Note 7 — Early Plant Retirements for additional information. In the second quarter of 2021, an overall decline in the asset group's portfolio value suggested that the carrying value of the New England asset group may be impaired. Generation completed a comprehensive review of the estimated undiscounted future cash flows of the New England asset group and concluded that the carrying value was not recoverable and that its fair value was less than its carrying value. As a result, a pre-tax impairment charge of $350 million was recorded in the second quarter of 2021 in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Contracted Wind Project In the third quarter of 2021, significant long-term operational issues anticipated for a specific wind turbine technology suggested that the carrying value of a contracted wind asset, located in Maryland and part of the EGRP joint venture, may be impaired. Generation completed a comprehensive review of the estimated undiscounted future cash flows and concluded that the carrying value of this contracted wind project was not recoverable and that its fair value was less than its carrying value. As a result, in the third quarter of 2021, a pre-tax impairment charge of $45 million was recorded in Operating and maintenance expense, $21 million of which was offset in Net income attributable to noncontrolling interests in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	9 Months Ended
Income Taxes (All Registrants)	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes (All Registrants)	Income Taxes (All Registrants) Rate Reconciliation The effective income tax rate from continuing operations varies from the U.S. federal statutory rate principally due to the following: Three Months Ended September 30, 2021 Exelon (a) Generation (a) ComEd (a) PECO (a)(b) BGE (a) (b) PHI (a) Pepco (a) DPL (a) ACE (a)(b) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.0 4.4 8.0 (4.1) (13.0) 5.0 3.4 6.4 7.0 Qualified NDT fund income 0.5 0.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.4) (0.7) (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (1.7) — (0.8) (16.2) (1.4) (1.3) (2.0) (0.6) (0.6) Production tax credits and other credits (1.0) (1.4) (0.5) — (0.9) (0.5) (0.5) (0.4) (0.5) Noncontrolling interests (0.4) (0.6) — — — — — — — Excess deferred tax amortization (6.8) — (7.6) (3.4) (17.3) (24.9) (17.6) (19.9) (41.4) Other (c) (4.8) (1.9) 0.3 (0.1) (0.8) — 0.1 (0.6) 0.8 Effective income tax rate 12.4% 21.7% 20.3% (2.8)% (12.5)% (0.8)% 4.4% 5.7% (13.9)% Three Months Ended September 30, 2020 Exelon (a) Generation (a) ComEd (a) PECO (a)(d) BGE (a)(d) PHI (a)(d) Pepco (a)(d) DPL (a)(d) ACE (a)(d) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 12.3 (10.3) 8.1 (6.2) 5.1 5.5 4.6 6.6 6.9 Qualified NDT fund income 13.2 47.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.4) (4.5) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (4.3) — (0.6) (23.3) (1.2) (1.5) (2.1) (0.4) (1.3) Production tax credits and other credits (3.0) (9.2) (0.4) — (0.8) (0.5) (0.5) (0.5) (0.4) Noncontrolling interests 0.8 2.9 — — — — — — — Excess deferred tax amortization (10.1) — (5.6) (3.8) (10.6) (24.9) (20.0) (23.6) (36.8) Tax Settlements (0.2) (0.7) — — — — — — — Other (0.8) (0.9) 1.1 (0.8) (0.3) 0.1 (0.4) 0.7 0.6 Effective income tax rate 27.5% 45.7% 23.4% (13.1)% 13.1% (0.5)% 2.5% 3.6% (10.3)% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) For PECO, the income tax benefit is primarily due to plant basis differences attributable to tax repair deductions. For BGE, the income tax benefit is primarily due to the Maryland multi-year plan which resulted in the acceleration of certain income tax benefits. For ACE, the income tax benefit is primarily due to a distribution rate case settlement which allows ACE to retain certain tax benefits. (c) For Exelon, "Other" is primarily driven by the reversal of the consolidating income tax adjustment recorded at Exelon Corporate in the first quarter of 2021 that was required pursuant to GAAP interim reporting guidance. (d) At PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to storm tax repair deductions. At BGE, PHI, Pepco, DPL and ACE, the lower effective tax rate is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. Nine Months Ended September 30, 2021 Exelon (a) Generation (b) ComEd (a) PECO (a)(c) BGE (a)(c) PHI (a) Pepco (a) DPL (a) ACE (a)(c) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.0 90.2 7.6 (2.6) (10.8) 4.6 2.5 6.5 7.3 Qualified NDT fund income 9.4 (1,932.6) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.8) 130.6 (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (3.9) — (0.7) (12.6) (1.5) (1.3) (1.9) (0.7) (0.6) Production tax credits and other credits (2.6) 425.1 (0.5) — (0.9) (0.5) (0.5) (0.4) (0.5) Noncontrolling interests (0.7) 145.2 — — — — — — — Excess deferred tax amortization (13.9) — (7.2) (3.3) (16.0) (22.8) (17.4) (19.7) (36.3) Other (d) 2.2 (229.5) (1.3) (0.2) (0.7) (0.3) (0.4) (0.2) — Effective income tax rate 13.7% (1,350.0)% 18.8% 2.3% (9.0)% 0.6% 3.3% 6.3% (9.3)% Nine Months Ended September 30, 2020 Exelon (a) Generation (a) ComEd (a)(e) PECO (a)(e) BGE (a)(e) PHI (a)(e) Pepco (a)(e) DPL (a)(e) ACE (a)(e) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 9.3 — 12.7 (3.4) 5.5 5.0 4.2 6.5 6.8 Qualified NDT fund income 3.2 10.0 — — — — — — — Deferred Prosecution Agreement payments 2.5 — 9.4 — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2) (3.2) (0.3) — (0.1) (0.2) (0.1) (0.3) (0.5) Plant basis differences (4.0) — (0.9) (15.9) (1.8) (2.2) (2.4) (0.5) (3.7) Production tax credits and other credits (2.6) (7.0) (0.4) — (0.4) (0.3) (0.3) (0.2) (0.4) Noncontrolling interests 1.0 3.1 — — — — — — — Excess deferred tax amortization (15.8) — (11.8) (3.5) (15.0) (45.3) (29.2) (53.6) (81.4) Tax Settlements (f) (5.0) (15.7) — — — — — — — Other 0.1 (0.5) 2.1 (0.5) (0.5) (0.6) (0.8) (1.1) — Effective income tax rate 8.5% 7.7% 31.8% (2.3)% 8.7% (22.6)% (7.6)% (28.2)% (58.2)% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) Generation recognized a loss before income taxes for the nine months ended September 30, 2021. As a result, a negative percentage represents an income tax expense for the period presented. (c) For PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to tax repair deductions. For BGE, the income tax benefit is primarily due to the Maryland multi-year plan which resulted in the acceleration of certain income tax benefits. For ACE, the income tax benefit is primarily due to a distribution rate case settlement which allows ACE to retain certain tax benefits. (d) For Exelon, "Other" is primarily driven by the consolidating income tax adjustment recorded at Exelon Corporate in the first quarter of 2021 that was required pursuant to GAAP interim reporting guidance. This incremental expense will reverse by year-end and will not have an impact on annual results. (e) For ComEd, the higher effective tax rate is primarily related to the nondeductible Deferred Prosecution Agreement payments. For PECO, the income tax benefit is primarily related to an increase in plant basis differences attributable to storm tax repairs deductions. For BGE, PHI, Pepco, DPL, and ACE, the income tax benefit is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. (f) Exelon's and Generation’s unrecognized federal and state tax benefits decreased in the first quarter of 2020 by approximately $411 million due to the settlement of a federal refund claim with IRS Appeals. The recognition of these tax benefits resulted in an increase to Exelon's and Generation’s net income of $76 million and $73 million, respectively, in the first quarter of 2020, reflecting a decrease to Exelon's and Generation's income tax expense of $67 million. Unrecognized Tax Benefits PHI and ACE have the following unrecognized tax benefits as of September 30, 2021 and December 31, 2020. Exelon's, Generation's, ComEd's, PECO's, BGE's, Pepco's, and DPL's amounts are not material. PHI ACE September 30, 2021 $ 56 $ 16 December 31, 2020 52 15 Reasonably possible the total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date As of September 30, 2021, ACE has approximately $14 million of unrecognized state tax benefits that could significantly decrease within the 12 months after the reporting date based on the outcome of pending court cases involving other taxpayers. The unrecognized tax benefit, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Other Income Tax Matters CENG Put Option (Exelon and Generation) On August 6, 2021, Generation and EDF entered into a settlement agreement pursuant to which Generation purchased EDF’s equity interest in CENG. Exelon and Generation recorded deferred tax liabilities of $290 million and $288 million, respectively, against Common Stock in Exelon’s Consolidated Balance Sheet and Membership Interest in Generation’s Consolidated Balance Sheet. The deferred tax liabilities represent the tax effect on the difference between the net purchase price and EDF’s noncontrolling interest as of August 6, 2021. The deferred tax liabilities will reverse during the remaining operating lives and during decommissioning of the CENG nuclear plants. See Note 2 – Mergers, Acquisitions, and Dispositions for additional information. Long-Term Marginal State Income Tax Rate (All Registrants) In the third quarter of 2021 and 2020, Exelon updated its marginal state income tax rates for changes in state apportionment. The changes in marginal rates in the third quarter of 2021 resulted in an increase of $27 million to the deferred income tax liability at Exelon, and a corresponding adjustment to income tax expense, net of federal taxes. The changes in marginal rates in the third quarter of 2020 resulted in an increase of $66 million and a decrease of $26 million to the deferred income tax liability at Exelon and Generation, respectively. Exelon and Generation recorded a corresponding adjustment to income tax expense, net of federal taxes. Allocation of Tax Benefits (All Registrants) Generation and the Utility Registrants are all party to an agreement with Exelon and other subsidiaries of Exelon that provides for the allocation of consolidated tax liabilities and benefits (Tax Sharing Agreement). The Tax Sharing Agreement provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. In addition, any net benefit attributable to Exelon is reallocated to the other Registrants. That allocation is treated as a contribution to the capital of the party receiving the benefit. The following table presents the allocation of federal tax benefits from Exelon under the Tax Sharing Agreement. Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 $ 64 $ 1 $ 19 $ — $ 17 $ 16 $ — $ — September 30, 2020 64 14 17 — 17 8 6 1

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	9 Months Ended
Retirement Benefits (All Registrants)	Sep. 30, 2021
Retirement Benefits [Abstract]
Retirement Benefits (All Registrants)	Retirement Benefits (All Registrants) Defined Benefit Pension and OPEB During the first quarter of 2021, Exelon received an updated valuation of its pension and OPEB to reflect actual census data as of January 1, 2021. This valuation resulted in an increase to the pension obligations of $33 million and a decrease to the OPEB obligations of $9 million. Additionally, accumulated other comprehensive loss increased by $1 million (after-tax) and regulatory assets and liabilities increased by $21 million and $1 million, respectively. The majority of the 2021 pension benefit cost for the Exelon-sponsored plans is calculated using an expected long-term rate of return on plan assets of 7.00% and a discount rate of 2.58%. The majority of the 2021 OPEB cost is calculated using an expected long-term rate of return on plan assets of 6.46% for funded plans and a discount rate of 2.51%. A portion of the net periodic benefit cost for all plans is capitalized in the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three and nine months ended September 30, 2021 and 2020. Pension Benefits OPEB Three Months Ended September 30, Three Months Ended September 30, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 110 $ 97 $ 20 $ 22 Interest cost 161 190 29 37 Expected return on assets (335) (317) (40) (41) Amortization of: Prior service cost (credit) 1 1 (8) (30) Actuarial loss 150 128 9 12 Settlement charges 12 8 — — Net periodic benefit cost $ 99 $ 107 $ 10 $ — Pension Benefits OPEB Nine Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 330 $ 290 $ 60 $ 67 Interest cost 481 569 86 114 Expected return on assets (1,003) (953) (119) (122) Amortization of: Prior service cost (credit) 3 3 (25) (92) Actuarial loss 449 384 27 36 Curtailment benefits — — (1) — Settlement charges 16 14 — — Net periodic benefit cost $ 276 $ 307 $ 28 $ 3 The amounts below represent the Registrants' allocated pension and OPEB costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant, and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant, and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2021 2020 2021 2020 Exelon $ 109 $ 107 $ 304 $ 310 Generation 36 30 92 89 ComEd 32 29 97 85 PECO 2 1 5 4 BGE 16 16 47 47 PHI 12 17 36 52 Pepco 2 4 5 11 DPL 1 2 2 6 ACE 3 3 8 10 Defined Contribution Savings Plans The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans for the three and nine months ended September 30, 2021 and 2020, respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plans Matching Contributions 2021 2020 2021 2020 Exelon $ 38 $ 37 $ 107 $ 104 Generation 14 14 40 41 ComEd 9 9 27 25 PECO 2 3 8 8 BGE 4 4 8 8 PHI 5 3 12 9 Pepco 1 1 3 3 DPL 1 1 3 2 ACE 1 — 2 1

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	9 Months Ended
Derivative Financial Instruments (All Registrants)	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments (All Registrants)	Derivative Financial Instruments (All Registrants) The Registrants use derivative instruments to manage commodity price risk, interest rate risk, and foreign exchange risk related to ongoing business operations. Authoritative guidance requires that derivative instruments be recognized as either assets or liabilities at fair value, with changes in fair value of the derivative recognized in earnings immediately. Other accounting treatments are available through special election and designation, provided they meet specific, restrictive criteria both at the time of designation and on an ongoing basis. These alternative permissible accounting treatments include NPNS, cash flow hedges, and fair value hedges. All derivative economic hedges related to commodities, referred to as economic hedges, are recorded at fair value through earnings at Generation and are offset by a corresponding regulatory asset or liability at ComEd. For all NPNS derivative instruments, accounts receivable or accounts payable are recorded when derivatives settle and revenue or expense is recognized in earnings as the underlying physical commodity is sold or consumed. Authoritative guidance about offsetting assets and liabilities requires the fair value of derivative instruments to be shown in the Combined Notes to Consolidated Financial Statements on a gross basis, even when the derivative instruments are subject to legally enforceable master netting agreements and qualify for net presentation in the Consolidated Balance Sheets. A master netting agreement is an agreement between two counterparties that may have derivative and non-derivative contracts with each other providing for the net settlement of all referenced contracts via one payment stream, which takes place as the contracts deliver, when collateral is requested or in the event of default. In the tables below, which present fair value balances, Generation’s energy-related economic hedges and proprietary trading derivatives are shown gross. The impact of the netting of fair value balances with the same counterparty that are subject to legally enforceable master netting agreements, as well as netting of cash collateral, including margin on exchange positions, is aggregated in the collateral and netting columns. Generation’s and ComEd’s use of cash collateral is generally unrestricted unless Generation or ComEd are downgraded below investment grade. Cash collateral held by PECO, BGE, Pepco, DPL, and ACE must be deposited in an unaffiliated major U.S. commercial bank or foreign bank with a U.S. branch office that meet certain qualifications. Commodity Price Risk (All Registrants) Each of the Registrants employ established policies and procedures to manage their risks associated with market fluctuations in commodity prices by entering into physical and financial derivative contracts, including swaps, futures, forwards, options, and short-term and long-term commitments to purchase and sell energy and commodity products. The Registrants believe these instruments, which are either determined to be non-derivative or classified as economic hedges, mitigate exposure to fluctuations in commodity prices. Generation. To the extent the amount of energy Generation produces differs from the amount of energy it has contracted to sell, Exelon and Generation are exposed to market fluctuations in the prices of electricity, fossil fuels, and other commodities. Within Exelon, Generation has the most exposure to commodity price risk. As such, Generation uses a variety of derivative and non-derivative instruments to manage the commodity price risk of its electric generation facilities, including power and gas sales, fuel and power purchases, natural gas transportation and pipeline capacity agreements, and other energy-related products marketed and purchased. To manage these risks, Generation may enter into fixed-price derivative or non-derivative contracts to hedge the variability in future cash flows from expected sales of power and gas and purchases of power and fuel. The objectives for executing such hedges include fixing the price for a portion of anticipated future electricity sales at a level that provides an acceptable return. Generation is also exposed to differences between the locational settlement prices of certain economic hedges and the hedged generating units. This price difference is actively managed through other instruments which include derivative congestion products, whose changes in fair value are recognized in earnings each period, and auction revenue rights, which are accounted for on an accrual basis. Additionally, Generation is exposed to certain market risks through its proprietary trading activities. The proprietary trading activities are a complement to Generation’s energy marketing portfolio but represent a small portion of Generation’s overall energy marketing activities and are subject to limits established by Exelon’s RMC. Utility Registrants . The Utility Registrants procure electric and natural gas supply through a competitive procurement process approved by each of the respective state utility commissions. The Utility Registrants’ hedging programs are intended to reduce exposure to energy and natural gas price volatility and have no direct earnings impact as the costs are fully recovered from customers through regulatory-approved recovery mechanisms. The following table provides a summary of the Utility Registrants’ primary derivative hedging instruments, listed by commodity and accounting treatment. Registrant Commodity Accounting Treatment Hedging Instrument ComEd Electricity NPNS Fixed price contracts based on all requirements in the IPA procurement plans. Electricity Changes in fair value of economic hedge recorded to an offsetting regulatory asset or liability (a) 20-year floating-to-fixed energy swap contracts beginning June 2012 based on the renewable energy resource procurement requirements in the Illinois Settlement Legislation of approximately 1.3 million MWhs per year. PECO Electricity NPNS Fixed price contracts for default supply requirements through full requirements contracts. Gas NPNS Fixed price contracts to cover about 10% of planned natural gas purchases in support of projected firm sales. BGE Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. Gas NPNS Fixed price contracts for between 10-20% of forecasted system supply requirements for flowing (i.e., non-storage) gas for the November through March period. Pepco Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. DPL Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. Gas NPNS Fixed and Index priced contracts through full requirements contracts. Changes in fair value of economic hedge recorded to an offsetting regulatory asset or liability (b) Exchange traded future contracts for up to 50% of estimated monthly purchase requirements each month, including purchases for storage injections. ACE Electricity NPNS Fixed price contracts for all BGS requirements through full requirements contracts. __________ (a) See Note 3 — Regulatory Matters of the 2020 Form 10-K for additional information. (b) The fair value of the DPL economic hedge is not material as of September 30, 2021 and December 31, 2020 and is not presented in the fair value tables below. The following tables provide a summary of the derivative fair value balances recorded by Exelon, Generation, and ComEd as of September 30, 2021 and December 31, 2020: Exelon Generation ComEd September 30, 2021 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 1,505 $ 19,631 $ 63 $ (790) $ (17,399) $ 1,505 $ — Mark-to-market derivative assets 661 3,612 5 (201) (2,755) 661 — Total mark-to-market derivative assets 2,166 23,243 68 (991) (20,154) 2,166 — Mark-to-market derivative liabilities (1,710) (18,490) (55) (559) 17,399 (1,705) (5) Mark-to-market derivative liabilities (720) (3,168) (3) (95) 2,755 (511) (209) Total mark-to-market derivative liabilities (2,430) (21,658) (58) (654) 20,154 (2,216) (214) Total mark-to-market derivative net (liabilities) assets $ (264) $ 1,585 $ 10 $ (1,645) $ — $ (50) $ (214) Exelon Generation ComEd December 31, 2020 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 639 $ 2,757 $ 40 $ 103 $ (2,261) $ 639 $ — Mark-to-market derivative assets 554 1,501 4 64 (1,015) 554 — Total mark-to-market derivative assets 1,193 4,258 44 167 (3,276) 1,193 — Mark-to-market derivative liabilities (293) (2,629) (23) 131 2,261 (260) (33) Mark-to-market derivative liabilities (472) (1,335) (2) 118 1,015 (204) (268) Total mark-to-market derivative liabilities (765) (3,964) (25) 249 3,276 (464) (301) Total mark-to-market derivative net assets (liabilities) $ 428 $ 294 $ 19 $ 416 $ — $ 729 $ (301) _________ (a) Exelon and Generation net all available amounts allowed under the derivative authoritative guidance in the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit, and other forms of non-cash collateral. As of September 30, 2021, $1 million of cash collateral posted with external counterparties and an additional $71 million of cash collateral posted with affiliates, including $50 million with ComEd, and as of December 31, 2020, $15 million of cash collateral held with external counterparties, was not offset against derivative positions because such collateral was not associated with any energy-related derivatives, was associated with accrual positions, or had no positions to offset as of the balance sheet date. (b) Includes $2,084 million held and $209 million posted of variation margin with the exchanges as of September 30, 2021 and December 31, 2020 respectively. Economic Hedges (Commodity Price Risk) Generation. For the three and nine months ended September 30, 2021 and 2020, Exelon and Generation recognized the following net pre-tax commodity mark-to-market gains (losses) which are also located in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. Three Months Ended Nine Months Ended 2021 2020 2021 2020 Income Statement Location (Loss) Gain (Loss) Gain Operating revenues $ (637) $ 39 $ (961) $ 238 Purchased power and fuel 1,392 209 2,209 224 Total Exelon and Generation $ 755 $ 248 $ 1,248 $ 462 In general, increases and decreases in forward market prices have a positive and negative impact, respectively, on Generation’s owned and contracted generation positions that have not been hedged. Generation hedges commodity price risk on a ratable basis over three-year periods. As of September 30, 2021, the percentage of expected generation hedged for the Mid-Atlantic, Midwest, New York, and ERCOT reportable segments is 96%-99% for the remainder of 2021. Proprietary Trading (Commodity Price Risk) Generation also executes commodity derivatives for proprietary trading purposes. Proprietary trading includes all contracts executed with the intent of benefiting from shifts or changes in market prices as opposed to those executed with the intent of hedging or managing risk. Gains and losses associated with proprietary trading are reported as Operating revenues in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income and are included in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. For the three and nine months ended September 30, 2021 and 2020, net pre-tax commodity mark-to-market gains and losses for Exelon and Generation were not material. The Utility Registrants do not execute derivatives for proprietary trading purposes. Interest Rate and Foreign Exchange Risk (Exelon and Generation) Generation utilizes interest rate swaps to manage its interest rate exposure and foreign currency derivatives to manage foreign exchange rate exposure associated with international commodity purchases in currencies other than U.S. dollars, both of which are treated as economic hedges. The notional amounts were $567 million and $665 million for Exelon and Generation as of September 30, 2021 and December 31, 2020, respectively. The mark-to-market derivative assets and liabilities as of September 30, 2021 and December 31, 2020 and the mark-to-market gains and losses for the three and nine months ended September 30, 2021 and 2020 were not material for Exelon and Generation. Credit Risk (All Registrants) The Registrants would be exposed to credit-related losses in the event of non-performance by counterparties on executed derivative instruments. The credit exposure of derivative contracts, before collateral, is represented by the fair value of contracts at the reporting date. Generation. For commodity derivatives, Generation enters into enabling agreements that allow for payment netting with its counterparties, which reduces Generation’s exposure to counterparty risk by providing for the offset of amounts payable to the counterparty against amounts receivable from the counterparty. Typically, each enabling agreement is for a specific commodity and so, with respect to each individual counterparty, netting is limited to transactions involving that specific commodity product, except where master netting agreements exist with a counterparty that allow for cross product netting. In addition to payment netting language in the enabling agreement, Generation’s credit department establishes credit limits, margining thresholds, and collateral requirements for each counterparty, which are defined in the derivative contracts. Counterparty credit limits are based on an internal credit review process that considers a variety of factors, including the results of a scoring model, leverage, liquidity, profitability, credit ratings by credit rating agencies, and risk management capabilities. To the extent that a counterparty’s margining thresholds are exceeded, the counterparty is required to post collateral with Generation as specified in each enabling agreement. Generation’s credit department monitors current and forward credit exposure to counterparties and their affiliates, both on an individual and an aggregate basis. The following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS, and payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of September 30, 2021. The tables further delineate that exposure by credit rating of the counterparties and provide guidance on the concentration of credit risk to individual counterparties. The amounts in the tables below exclude credit risk exposure from individual retail counterparties, nuclear fuel procurement contracts, and exposure through RTOs, ISOs, NYMEX, ICE, NASDAQ, NGX, and Nodal commodity exchanges. Rating as of September 30, 2021 Total Exposure Before Credit Collateral Credit Collateral (a) Net Exposure Number of Counterparties Greater than 10% of Net Exposure Net Exposure of Counterparties Greater than 10% of Net Exposure Investment grade $ 701 $ 254 $ 447 — $ — Non-investment grade 23 2 21 — — No external ratings Internally rated — investment grade 110 1 109 — — Internally rated — non-investment grade 309 48 261 — — Total $ 1,143 $ 305 $ 838 — $ — Net Credit Exposure by Type of Counterparty As of September 30, 2021 Financial institutions $ 53 Investor-owned utilities, marketers, power producers 652 Energy cooperatives and municipalities 62 Other 71 Total $ 838 _________ (a) As of September 30, 2021, credit collateral held from counterparties where Generation had credit exposure included $188 million of cash and $117 million of letters of credit. The credit collateral does not include non-liquid collateral. Utility Registrants. The Utility Registrants have contracts to procure electric and natural gas supply that provide suppliers with a certain amount of unsecured credit. If the exposure on the supply contract exceeds the amount of unsecured credit, the suppliers may be required to post collateral. The net credit exposure is mitigated primarily by the ability to recover procurement costs through customer rates. As of September 30, 2021, the amount of cash collateral held with external counterparties by ComEd, BGE, and DPL was $56 million, $21 million, and $25 million, respectively, which is recorded in Other Current Liabilities in ComEd’s, BGE’s, and DPL’s Consolidated Balance Sheets. The amounts for PECO, Pepco, and ACE as of September 30, 2021 and for the Utility Registrants as of December 31, 2020 are not material. The amount for ComEd as of September 30, 2021 does not include cash collateral held from Generation, which is disclosed in the notes to the derivative fair value balances tables above. Credit-Risk-Related Contingent Features (All Registrants) Generation. As part of the normal course of business, Generation routinely enters into physically or financially settled contracts for the purchase and sale of electric capacity, electricity, fuels, emissions allowances, and other energy-related products. Certain of Generation’s derivative instruments contain provisions that require Generation to post collateral. Generation also enters into commodity transactions on exchanges where the exchanges act as the counterparty to each trade. Transactions on the exchanges must adhere to comprehensive collateral and margining requirements. This collateral may be posted in the form of cash or credit support with thresholds contingent upon Generation’s credit rating from each of the major credit rating agencies. The collateral and credit support requirements vary by contract and by counterparty. These credit-risk-related contingent features stipulate that if Generation were to be downgraded or lose its investment grade credit rating (based on its senior unsecured debt rating), it would be required to provide additional collateral. This incremental collateral requirement allows for the offsetting of derivative instruments that are assets with the same counterparty, where the contractual right of offset exists under applicable master netting agreements. In the absence of expressly agreed-to provisions that specify the collateral that must be provided, collateral requested will be a function of the facts and circumstances of the situation at the time of the demand. In this case, Generation believes an amount of several months of future payments (i.e., capacity payments) rather than a calculation of fair value is the best estimate for the contingent collateral obligation, which has been factored into the disclosure below. The aggregate fair value of all derivative instruments with credit-risk related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Features September 30, 2021 December 31, 2020 Gross fair value of derivative contracts containing this feature (a) $ (5,289) $ (834) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 2,735 537 Net fair value of derivative contracts containing this feature (c) $ (2,554) $ (297) _________ (a) Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk related contingent features ignoring the effects of master netting agreements. (b) Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which Generation could potentially be required to post collateral. (c) Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based. As of September 30, 2021 and December 31, 2020, Exelon and Generation posted or held the following amounts of cash collateral and letters of credit on derivative contracts with external counterparties, after giving consideration to offsetting derivative and non-derivative positions under master netting agreements. September 30, 2021 December 31, 2020 Cash collateral posted $ 299 $ 511 Letters of credit posted 477 226 Cash collateral held 1,872 110 Letters of credit held 130 40 Additional collateral required in the event of a credit downgrade below investment grade 3,001 1,432 Generation entered into supply forward contracts with certain utilities, including PECO and BGE, with one-sided collateral postings only from Generation. If market prices fall below the benchmark price levels in these contracts, the utilities are not required to post collateral. However, when market prices rise above the benchmark price levels, counterparty suppliers, including Generation, are required to post collateral once certain unsecured credit limits are exceeded. Utility Registrants The Utility Registrants’ electric supply procurement contracts do not contain provisions that would require them to post collateral.

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	9 Months Ended
Debt and Credit Agreements (All Registrants)	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	Debt and Credit Agreements (All Registrants) Short-Term Borrowings Exelon Corporate, ComEd, and BGE meet their short-term liquidity requirements primarily through the issuance of commercial paper. Generation and PECO meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the Exelon intercompany money pool. Pepco, DPL, and ACE meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the PHI intercompany money pool. PHI Corporate meets its short-term liquidity requirements primarily through the issuance of short-term notes and the Exelon intercompany money pool. The Registrants may use their respective credit facilities for general corporate purposes, including meeting short-term funding requirements and the issuance of letters of credit. Commercial Paper The following table reflects the Registrants' commercial paper programs as of September 30, 2021 and December 31, 2020. PECO and BGE had no commercial paper borrowings as of September 30, 2021 and December 31, 2020. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2021 December 31, 2020 September 30, 2021 December 31, 2020 Exelon (a) $ 287 $ 1,031 0.19 % 0.25 % Generation — 340 — % 0.27 % ComEd — 323 — % 0.23 % PHI (b) 287 368 0.19 % 0.24 % Pepco 40 35 0.15 % 0.22 % DPL 22 146 0.15 % 0.24 % ACE 225 187 0.20 % 0.25 % __________ (a) Exelon Corporate had no outstanding commercial paper borrowings as of September 30, 2021 and December 31, 2020. (b) Represents the consolidated amounts of Pepco, DPL, and ACE. See Note 17 — Debt and Credit Agreements of the Exelon 2020 Form 10-K for additional information on the Registrants' credit facilities. Short-Term Loan Agreements On March 23, 2017, Exelon Corporate entered into a term loan agreement for $500 million. The loan agreement was renewed on March 17, 2021 and will expire on March 16, 2022. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.65% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's Consolidated Balance Sheets within Short-term borrowings. On March 24, 2021, Exelon Corporate entered into a 9-month term loan agreement for $200 million. The loan agreement has an expiration of December 24, 2021. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.65% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's Consolidated Balance Sheets within Short-term borrowings. On March 31, 2021, Exelon Corporate entered into a 9-month and 364-day term loan agreement for $150 million each with variable interest rates of LIBOR plus 0.65% and expiration dates of December 31, 2021 and March 30, 2022, respectively. The loan agreements are reflected in Exelon's Consolidated Balance Sheets within Short-term borrowings. On March 19, 2020, Generation entered into a term loan agreement for $200 million. The loan agreement was renewed on March 17, 2021 and will expire on March 16, 2022. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.875% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's and Generation's Consolidated Balance Sheets within Short-term borrowings. On March 31, 2020, Generation entered into a term loan agreement for $300 million. The loan agreement was renewed on March 30, 2021 and will expire on March 29, 2022. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.70% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's and Generation's Consolidated Balance Sheets within Short-term borrowings. On August 6, 2021, Generation entered into a 364-day term loan agreement for $880 million with a variable interest rate of LIBOR plus 0.875% until March 31, 2022 and a rate of LIBOR plus 1% thereafter and all indebtedness thereunder is unsecured. The loan agreement has an expiration date of August 5, 2022 and is reflected in Short-term borrowings in Exelon's and Generation's Consolidated Balance Sheets. On January 25, 2021, ComEd entered into two 90-day term loan agreements for $125 million each with variable interest rates of LIBOR plus 0.50% and LIBOR plus 0.75%, respectively. ComEd repaid the term loans on March 9, 2021. Bilateral Credit Agreements On January 11, 2013, Generation entered into a bilateral credit agreement for $100 million. The agreement was renewed on March 1, 2021 with a maturity date of March 1, 2023. On February 21, 2019, Generation entered into a bilateral credit agreement for $100 million. The agreement was renewed on March 31, 2021 with a maturity date of March 31, 2022. On January 5, 2016, Generation entered into a bilateral credit agreement for $150 million. The agreement was renewed on April 2, 2021 with a maturity date of April 5, 2023. On October 26, 2012, Generation entered into a bilateral credit agreement for $200 million. The agreement had a maturity date of October 22, 2021, however, was terminated on August 27, 2021. See Note 17 — Debt and Credit Agreements of the Exelon 2020 Form 10-K for additional information on Generation's bilateral credit agreements. Credit Agreements On July 15, 2021, each of the Registrants' respective syndicated revolving credit facilities had their maturity dates extended to May 26, 2024. Long-Term Debt Issuance of Long-Term Debt During the nine months ended September 30, 2021, the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Long-Term Software License Agreements 3.62 % December 1, 2025 $ 4 Procurement of software licenses. Generation West Medway II LIBOR + 3% (a) March 31, 2026 150 Funding for general corporate purposes. Generation Energy Efficiency Project Financing (b) 2.53 % November 30, 2021 1 Funding to install energy conservation measures for the Fort AP Hill project. Generation Energy Efficiency Project Financing (b) 4.24 % November 30, 2021 1 Funding to install energy conservation measures for the Marine Corps. Logistics Project. ComEd First Mortgage Bonds, Series 130 3.13 % March 15, 2051 700 Repay a portion of outstanding commercial paper obligations and two outstanding term loans, and to fund other general corporate purposes. ComEd First Mortgage Bonds, Series 131 2.75 % September 1, 2051 450 Refinance existing indebtedness and for general corporate purposes. PECO First and Refunding Mortgage Bonds 3.05 % March 15, 2051 375 Funding for general corporate purposes. PECO First and Refunding Mortgage Bonds 2.85 % September 15, 2051 375 Refinance existing indebtedness and for general corporate purposes. BGE Senior Notes 2.25 % June 15, 2031 600 Repay a portion of outstanding commercial paper obligations, repay existing indebtedness, and to fund other general corporate purposes. Pepco First Mortgage Bonds 2.32 % March 30, 2031 150 Repay existing indebtedness and for general corporate purposes. Pepco First Mortgage Bonds 3.29 % September 28, 2051 125 Repay existing indebtedness and for general corporate purposes. DPL First Mortgage Bonds 3.24 % March 30, 2051 125 Repay existing indebtedness and for general corporate purposes. ACE First Mortgage Bonds 2.30 % March 15, 2031 350 Refinance existing indebtedness, repay outstanding commercial paper obligations, and for general corporate purposes. __________ (a) The nonrecourse debt has an average blended interest rate. (b) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt. Debt Covenants As of September 30, 2021, the Registrants are in compliance with debt covenants. Nonrecourse Debt Exelon and Generation have issued nonrecourse debt financing. Borrowings under these agreements are secured by the assets and equity of each respective project. The lenders do not have recourse against Exelon or Generation in the event of a default. West Medway II, LLC. On May 13, 2021, West Medway II, LLC (West Medway II), an indirect subsidiary of Generation, entered into a financing agreement for a $150 million nonrecourse senior secured term loan credit facility with a maturity date of March 31, 2026. The term loan bears interest at an average blended interest rate of LIBOR plus 3%, paid quarterly. In addition to the financing, West Medway II, entered into interest rate swaps with an initial notional amount of $113 million at an interest rate of 0.61%, paid quarterly, to manage a portion of the interest rate exposure in connection with the financing. The net proceeds were distributed to Generation for general corporate purposes. Generation’s interests in West Medway II, were pledged as collateral for this financing. As of September 30, 2021, approximately $145 million was outstanding. See Note 17 — Debt and Credit Agreements of the Exelon 2020 Form 10-K for additional information on nonrecourse debt and Note 12 — Derivative Financial Instruments for additional information on interest rate swaps.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	Fair Value of Financial Assets and Liabilities (All Registrants) Exelon measures and classifies fair value measurements in accordance with the hierarchy as defined by GAAP. The hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that the Registrants have the ability to liquidate as of the reporting date. • Level 2 - inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3 - unobservable inputs, such as internally developed pricing models or third-party valuations for the asset or liability due to little or no market activity for the asset or liability. Fair Value of Financial Liabilities Recorded at Amortized Cost The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2021 and December 31, 2020. The Registrants have no financial liabilities classified as Level 1. The carrying amounts of the Registrants’ short-term liabilities as presented in their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. September 30, 2021 December 31, 2020 Carrying Amount Fair Value Carrying Amount Fair Value Level 2 Level 3 Total Level 2 Level 3 Total Long-Term Debt, including amounts due within one year (a) Exelon $ 38,644 $ 40,570 $ 3,289 $ 43,859 $ 36,912 $ 40,688 $ 3,064 $ 43,752 Generation 6,130 5,835 1,111 6,946 6,087 5,648 1,208 6,856 ComEd 9,772 11,344 — 11,344 8,983 11,117 — 11,117 PECO 4,196 4,738 50 4,788 3,753 4,553 50 4,603 BGE 3,960 4,416 — 4,416 3,664 4,366 — 4,366 PHI 7,482 6,030 2,128 8,158 7,006 6,099 1,806 7,905 Pepco 3,441 3,226 990 4,216 3,165 3,336 748 4,084 DPL 1,808 1,433 559 1,992 1,677 1,484 455 1,939 ACE 1,510 1,107 579 1,686 1,413 1,018 602 1,620 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 479 $ 479 $ 390 $ — $ 467 $ 467 ComEd 205 — 255 255 205 — 246 246 PECO 184 — 224 224 184 — 221 221 SNF Obligation Exelon $ 1,209 $ 1,021 $ — $ 1,021 $ 1,208 $ 909 $ — $ 909 Generation 1,209 1,021 — 1,021 1,208 909 — 909 __________ (a) Includes unamortized debt issuance costs which are not fair valued. Recurring Fair Value Measurements The following tables present assets and liabilities measured and recorded at fair value in the Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2021 and December 31, 2020: Exelon and Generation Exelon Generation As of September 30, 2021 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 2,573 $ — $ — $ — $ 2,573 $ 1,673 $ — $ — $ — $ 1,673 NDT fund investments Cash equivalents (b) 647 135 — — 782 647 135 — — 782 Equities 4,373 1,717 1 1,559 7,650 4,373 1,717 1 1,559 7,650 Fixed income Corporate debt (c) — 1,155 287 — 1,442 — 1,155 287 — 1,442 U.S. Treasury and agencies 2,192 29 — — 2,221 2,192 29 — — 2,221 Foreign governments — 54 — — 54 — 54 — — 54 State and municipal debt — 29 — — 29 — 29 — — 29 Other 31 29 — 1,259 1,319 31 29 — 1,259 1,319 Fixed income subtotal 2,223 1,296 287 1,259 5,065 2,223 1,296 287 1,259 5,065 Private credit — — 187 592 779 — — 187 592 779 Private equity — — — 654 654 — — — 654 654 Real estate — — — 802 802 — — — 802 802 NDT fund investments subtotal (d)(e) 7,243 3,148 475 4,866 15,732 7,243 3,148 475 4,866 15,732 Rabbi trust investments Cash equivalents 65 — — — 65 4 — — — 4 Mutual funds 104 — — — 104 35 — — — 35 Fixed income — 10 — — 10 — — — — — Life insurance contracts — 99 34 — 133 — 33 — — 33 Rabbi trust investments subtotal 169 109 34 — 312 39 33 — — 72 Investments in equities (f) 137 — — — 137 137 — — — 137 Commodity derivative assets Economic hedges 5,527 10,633 7,083 — 23,243 5,527 10,633 7,083 — 23,243 Proprietary trading — 56 12 — 68 — 56 12 — 68 Effect of netting and allocation of collateral (g)(h) (4,468) (9,869) (6,808) — (21,145) (4,468) (9,869) (6,808) — (21,145) Commodity derivative assets subtotal 1,059 820 287 — 2,166 1,059 820 287 — 2,166 DPP consideration — 501 — — 501 — 501 — — 501 Exelon Generation As of September 30, 2021 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Total assets 11,181 4,578 796 4,866 21,421 10,151 4,502 762 4,866 20,281 Liabilities Commodity derivative liabilities Economic hedges (4,126) (9,192) (8,554) — (21,872) (4,126) (9,192) (8,340) — (21,658) Proprietary trading — (32) (26) — (58) — (32) (26) — (58) Effect of netting and allocation of collateral (g)(h) 4,123 9,159 6,218 — 19,500 4,123 9,159 6,218 — 19,500 Commodity derivative liabilities subtotal (3) (65) (2,362) — (2,430) (3) (65) (2,148) — (2,216) Deferred compensation obligation — (149) — — (149) — (44) — — (44) Total liabilities (3) (214) (2,362) — (2,579) (3) (109) (2,148) — (2,260) Total net assets (liabilities) $ 11,178 $ 4,364 $ (1,566) $ 4,866 $ 18,842 $ 10,148 $ 4,393 $ (1,386) $ 4,866 $ 18,021 Exelon Generation As of December 31, 2020 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 686 $ — $ — $ — $ 686 $ 124 $ — $ — $ — $ 124 NDT fund investments Cash equivalents (b) 210 95 — — 305 210 95 — — 305 Equities 3,886 2,077 — 1,562 7,525 3,886 2,077 — 1,562 7,525 Fixed income Corporate debt (c) — 1,485 285 — 1,770 — 1,485 285 — 1,770 U.S. Treasury and agencies 1,871 126 — — 1,997 1,871 126 — — 1,997 Foreign governments — 56 — — 56 — 56 — — 56 State and municipal debt — 101 — — 101 — 101 — — 101 Other — 41 — 961 1,002 — 41 — 961 1,002 Fixed income subtotal 1,871 1,809 285 961 4,926 1,871 1,809 285 961 4,926 Private credit — — 212 629 841 — — 212 629 841 Private equity — — — 504 504 — — — 504 504 Real estate — — — 679 679 — — — 679 679 NDT fund investments subtotal (d)(e) 5,967 3,981 497 4,335 14,780 5,967 3,981 497 4,335 14,780 Rabbi trust investments Cash equivalents 60 — — — 60 4 — — — 4 Mutual funds 91 — — — 91 29 — — — 29 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 87 34 — 121 — 28 — — 28 Rabbi trust investments subtotal 151 98 34 — 283 33 28 — — 61 Investments in equities (f) 195 — — — 195 195 — — — 195 Commodity derivative assets Economic hedges 745 1,914 1,599 — 4,258 745 1,914 1,599 — 4,258 Proprietary trading — 17 27 — 44 — 17 27 — 44 Exelon Generation As of December 31, 2020 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Effect of netting and allocation of collateral (g)(h) (607) (1,597) (905) — (3,109) (607) (1,597) (905) — (3,109) Commodity derivative assets subtotal 138 334 721 — 1,193 138 334 721 — 1,193 DPP consideration — 639 — — 639 — 639 — — 639 Total assets 7,137 5,052 1,252 4,335 17,776 6,457 4,982 1,218 4,335 16,992 Liabilities Commodity derivative liabilities Economic hedges (682) (1,928) (1,655) — (4,265) (682) (1,928) (1,354) — (3,964) Proprietary trading — (21) (4) — (25) — (21) (4) — (25) Effect of netting and allocation of collateral (g)(h) 540 1,918 1,067 — 3,525 540 1,918 1,067 — 3,525 Commodity derivative liabilities subtotal (142) (31) (592) — (765) (142) (31) (291) — (464) Deferred compensation obligation — (145) — — (145) — (42) — — (42) Total liabilities (142) (176) (592) — (910) (142) (73) (291) — (506) Total net assets $ 6,995 $ 4,876 $ 660 $ 4,335 $ 16,866 $ 6,315 $ 4,909 $ 927 $ 4,335 $ 16,486 __________ (a) Exelon excludes cash of $689 million and $409 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $222 million and $59 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $54 million and $53 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $292 million and $171 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $54 million and $20 million at September 30, 2021 and December 31, 2020, respectively. (b) Includes $109 million and $116 million of cash received from outstanding repurchase agreements at September 30, 2021 and December 31, 2020, respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (e) below. (c) Includes investments in equities sold short of $(50) million and $(62) million as of September 30, 2021 and December 31, 2020, respectively, held in an investment vehicle primarily to hedge the equity option component of its convertible debt. (d) Includes net derivative liabilities of less than $1 million and net derivative assets of $2 million, which have total notional amounts of $728 million and $1,043 million at September 30, 2021 and December 31, 2020, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the periods ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (e) Excludes net liabilities of $130 million and $181 million at September 30, 2021 and December 31, 2020, respectively, which include certain derivative assets that have notional amounts of $194 million and $104 million at September 30, 2021 and December 31, 2020, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (f) Includes equity investments held by Generation which were previously designated as equity investments without readily determinable fair value but are now publicly traded and therefore have readily determinable fair values. The first investment became publicly traded in the fourth quarter of 2020. Generation records the fair value of these investments in Other current assets in Exelon's and Generation's Consolidated Balance Sheets based on the quoted market prices of the stocks as of the respective balance sheet date. There were no equity investments without readily determinable fair value that became publicly traded during the third quarter of 2021. For investments that became publicly traded during the first half of 2021, unrealized gains o f $220 million were recorded in Other, net in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. (g) Collateral (received) from counterparties, net of collateral paid to counterparties, totaled $(345) million, $(710) million, and $(590) million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of September 30, 2021. Collateral (received)/posted from counterparties, net of collateral paid to counterparties, totaled $(67) million, $321 million, and $162 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of December 31, 2020. (h) Includes $2,084 million held and $209 million posted of variation margin with the exchanges as of September 30, 2021 and December 31, 2020, respectively. As of September 30, 2021, Exelon and Generation have outstanding commitments to invest in private credit, private equity, and real estate investments of approximately $359 million, $174 million, and $371 million, respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation held investments without readily determinable fair values with carrying amounts of $44 million and $32 million as of September 30, 2021, respectively. Exelon and Generation held investments without readily determinable fair values with carrying amounts of $73 million and $55 million as of December 31, 2020, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three and nine months ended September 30, 2021 and for the year ended December 31, 2020. ComEd, PECO, and BGE ComEd PECO BGE As of September 30, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 309 $ — $ — $ 309 $ 247 $ — $ — $ 247 $ 169 $ — $ — $ 169 Rabbi trust investments Mutual funds — — — — 10 — — 10 14 — — 14 Life insurance contracts — — — — — 15 — 15 — — — — Rabbi trust investments subtotal — — — — 10 15 — 25 14 — — 14 Total assets 309 — — 309 257 15 — 272 183 — — 183 Liabilities Deferred compensation obligation — (9) — (9) — (8) — (8) — (6) — (6) Mark-to-market derivative liabilities (b) — — (214) (214) — — — — — — — — Total liabilities — (9) (214) (223) — (8) — (8) — (6) — (6) Total net assets (liabilities) $ 309 $ (9) $ (214) $ 86 $ 257 $ 7 $ — $ 264 $ 183 $ (6) $ — $ 177 ComEd PECO BGE As of December 31, 2020 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 285 $ — $ — $ 285 $ 8 $ — $ — $ 8 $ 120 $ — $ — $ 120 Rabbi trust investments Mutual funds — — — — 9 — — 9 10 — — 10 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 10 — — 10 Total assets 285 — — 285 17 13 — 30 130 — — 130 Liabilities Deferred compensation obligation — (8) — (8) — (9) — (9) — (5) — (5) Mark-to-market derivative liabilities (b) — — (301) (301) — — — — — — — — Total liabilities — (8) (301) (309) — (9) — (9) — (5) — (5) Total net assets (liabilities) $ 285 $ (8) $ (301) $ (24) $ 17 $ 4 $ — $ 21 $ 130 $ (5) $ — $ 125 __________ (a) ComEd excludes cash of $145 million and $83 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $107 million and $37 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $44 million and $43 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $105 million and $18 million at September 30, 2021 and December 31, 2020, respectively. BGE excludes cash of $56 million and $24 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $27 million and $1 million at September 30, 2021 and December 31, 2020, respectively. (b) The Level 3 balance consists of the current and noncurrent liability of $5 million and $209 million, respectively, at September 30, 2021 and $33 million and $268 million, respectively, at December 31, 2020 related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL, and ACE As of September 30, 2021 As of December 31, 2020 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 100 $ — $ — $ 100 $ 86 $ — $ — $ 86 Rabbi trust investments Cash equivalents 59 — — 59 55 — — 55 Mutual funds 14 — — 14 14 — — 14 Fixed income — 10 — 10 — 11 — 11 Life insurance contracts — 27 34 61 — 26 34 60 Rabbi trust investments subtotal 73 37 34 144 69 37 34 140 Total assets 173 37 34 244 155 37 34 226 Liabilities Deferred compensation obligation — (19) — (19) — (17) — (17) Total liabilities — (19) — (19) — (17) — (17) Total net assets $ 173 $ 18 $ 34 $ 225 $ 155 $ 20 $ 34 $ 209 Pepco DPL ACE As of September 30, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 36 $ — $ — $ 36 $ 26 $ — $ — $ 26 $ 14 $ — $ — $ 14 Rabbi trust investments Cash equivalents 58 — — 58 — — — — — — — — Fixed income — — — — — — — — — — — — Life insurance contracts — 27 34 61 — — — — — — — — Rabbi trust investments subtotal 58 27 34 119 — — — — — — — — Total assets 94 27 34 155 26 — — 26 14 — — 14 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 94 $ 25 $ 34 $ 153 $ 26 $ — $ — $ 26 $ 14 $ — $ — $ 14 Pepco DPL ACE As of December 31, 2020 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 35 $ — $ — $ 35 $ — $ — $ — $ — $ 13 $ — $ — $ 13 Rabbi trust investments Cash equivalents 53 — — 53 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 34 60 — — — — — — — — Rabbi trust investments subtotal 53 28 34 115 — — — — — — — — Total assets 88 28 34 150 — — — — 13 — — 13 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 88 $ 26 $ 34 $ 148 $ — $ — $ — $ — $ 13 $ — $ — $ 13 __________ (a) PHI excludes cash of $57 million and $74 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $19 million and $30 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at September 30, 2021 and December 31, 2020, respectively. DPL excludes cash of $13 million and $15 million at September 30, 2021 and December 31, 2020, respectively. ACE excludes cash of $16 million and $17 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Reconciliation of Level 3 Assets and Liabilities The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2021 and 2020: Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2021 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2021 $ (235) $ 461 $ (465) $ (4) $ (265) $ 34 $ — Total realized / unrealized gains (losses) Included in net income (967) 3 (970) (a) (967) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11) Included in regulatory assets 62 — — — 51 (b) — 11 Change in collateral (413) — (413) (413) — — — Purchases, sales, and settlements Purchases 8 2 6 8 — — — Sales 6 — 6 6 — — — Settlements (2) (2) — (2) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 (27) — (27) (c) (27) — — — Balance at September 30, 2021 $ (1,566) $ 475 $ (1,861) $ (1,386) $ (214) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2021 $ (1,001) $ 3 $ (1,004) $ (1,001) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine months ended September 30, 2021 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2020 $ 660 $ 497 $ 430 $ 927 $ (301) $ 34 $ — Total realized / unrealized gains (losses) Included in net income (1,600) 4 (1,606) (a) (1,602) — 2 — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets 105 — — — 87 (b) — 18 Change in collateral (751) — (751) (751) — — — Purchases, sales, and settlements Purchases 123 3 120 123 — — — Sales 7 — 7 7 — — — Settlements (50) (48) — (48) — (2) — Transfers into Level 3 4 1 3 (c) 4 — — — Transfers out of Level 3 (64) — (64) (c) (64) — — — Balance as of September 30, 2021 $ (1,566) $ 475 $ (1,861) $ (1,386) $ (214) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2021 $ (1,521) $ 4 $ (1,527) $ (1,523) $ — $ 2 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2020 $ 883 $ 499 $ 659 $ 1,158 $ (318) $ 43 $ — Total realized / unrealized gains (losses) Included in net income (327) 3 (318) (a) (315) — (12) — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets/liabilities 32 — — — 14 (b) — 18 Change in collateral (79) — (79) (79) — — — Purchases, sales, and settlements Purchases 66 1 65 66 — — — Sales (3) — (3) (3) — — — Settlements — (3) — (3) — 3 — Transfers out of Level 3 9 — 9 (c) 9 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (222) $ 3 $ (213) $ (210) $ — $ (12) $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2019 $ 1,068 $ 511 $ 817 $ 1,328 $ (301) $ 41 $ — Total realized / unrealized gains (losses) Included in net income (483) 1 (474) (a) (473) — (10) — Included in noncurrent payables to affiliates — 17 — 17 — — (17) Included in regulatory assets 14 — — — (3) (b) — 17 Change in collateral (120) — (120) (120) — — — Purchases, sales, and settlements Purchases 136 6 130 136 — — — Sales (27) — (27) (27) — — — Settlements (15) (18) — (18) — 3 — Transfers into Level 3 (5) 1 (6) (c) (5) — — — Transfers out of Level 3 13 — 13 (c) 13 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized (losses) gains related to assets and liabilities as of September 30, 2020 $ (107) $ 1 $ (98) $ (97) $ — $ (10) $ — __________ (a) Includes an addition of $34 million for realized losses and a reduction of $80 million for realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2021. Includes a reduction of $105 million and $376 million for realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2020. (b) Includes $49 million of increases in fair value and an increase for realized losses due to settlements of $2 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2021. Includes $72 million of increases in fair value and an increase for realized losses due to settlements of $15 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2021. Includes $9 million of increases in fair value and an increase for realized losses due to settlements of $5 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2020. Includes $26 million of decrease in fair value and an increase for realized losses due to settlements of $23 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2020. (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts. The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2021 and 2020: Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total (losses) gains included in net income for the three months ended September 30, 2021 $ (1,274) $ 304 $ — $ 3 $ (1,274) $ 304 $ 3 $ — Total (losses) gains included in net income for the nine months ended September 30, 2021 (1,944) 338 2 4 (1,944) 338 4 2 Total unrealized (losses) gains for the three months ended September 30, 2021 (1,361) 357 — 3 (1,361) 357 3 — Total unrealized (losses) gains for the nine months ended September 30, 2021 (1,969) 443 2 4 (1,969) 443 4 2 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total losses included in net income for the three months ended September 30, 2020 $ (305) $ (13) $ (12) $ — $ (305) $ (13) $ — $ (12) Total losses included in net income for the nine months ended September 30, 2020 (370) (104) (10) — (370) (104) — (10) Total unrealized (losses) gains for the three months ended September 30, 2020 (216) 3 (12) 3 (216) 3 3 (12) Total unrealized gains (losses) for the nine months ended September 30, 2020 (50) (48) (10) 1 (50) (48) 1 (10) Valuation Techniques Used to Determine Fair Value Exelon’s valuation techniques used to measure the fair value of the assets and liabilities shown in the tables below are in accordance with the policies discussed in Note 18 — Fair Value of Financial Assets and Liabilities of the Exelon 2020 Form 10-K. Valuation Techniques Used to Determine Net asset Value (Exelon and Generation) Certain NDT Fund Investments are not classified within the fair value hierarchy and are included under the heading “Not subject to leveling” in the table above. These investments are measured at fair value using NAV per share as a practical expedient and include commingled funds, mutual funds which are not publicly quoted, managed private credit funds, private equity and real estate funds. For commingled funds and mutual funds, which are not publicly quoted, the fair value is primarily derived from the quoted prices in active markets on the underlying securities and can typically be redeemed monthly with 30 or less days of notice and without further restrictions. For managed private credit funds, the fair value is determined using a combination of valuation models including cost models, market models, and income models and typically cannot be redeemed until maturity of the term loan. Private equity and real estate investments include those in limited partnerships that invest in operating companies and real estate holding companies that are not publicly traded on a stock exchange, such as, leveraged buyouts, growth capital, venture capital, distressed investments, investments in natural resources, and direct investments in pools of real estate properties. These investments typically cannot be redeemed and are generally liquidated over a period of 8 to 10 years from the initial investment date, which is based on Exelon’s understanding of the investment funds. Private equity and real estate valuations are reported by the fund manager and are based on the valuation of the underlying investments, which include inputs such as cost, operating results, discounted future cash flows, market based comparable data, and independent appraisals from sources with professional qualifications. These valuation inputs are unobservable. Mark-to-Market Derivatives (Exelon, Generation, and ComEd) The table below discloses the significant inputs to the forward curve used to value mark-to-market derivatives. Type of trade Fair Value at September 30, 2021 Fair Value at December 31, 2020 Valuation Unobservable 2021 Range & Arithmetic Average 2020 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ (1,257) $ 245 Discounted Forward power $9.77 - $301 $55 $2.25 - $163 $30 Forward gas $1.76 - $23.00 $4.16 $1.57 - $7.88 $2.59 Option Volatility 35% - 197% 49% 11% - 237% 32% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ (14) $ 23 Discounted Forward power $16 - $156 $53 $10 - $106 $27 Mark-to-market derivatives (Exelon and ComEd) $ (214) $ (301) Discounted Forward heat (c) 9x - 10x 9.13x 8x - 9x 8.85x Marketability 3% - 7% 4.77% 3% - 8% 4.93% Renewable 95% - 122% 100% 91% - 123% 99% __________ (a) The valuation techniques, unobservable inputs, ranges and arithmetic averages are the same for the asset and liability positions. (b) The fair values do not include cash collateral (received)/posted on level three positions of $(590) million and $162 million as of September 30, 2021 and December 31, 2020, respectively. (c) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery. The inputs listed above, which are as of the balance sheet date, would have a direct impact on the fair values of the above instruments if they were adjusted. The significant unobservable inputs used in the fair value measurement of Generation’s commodity derivatives are forward commodity prices and for options is price volatility. Increases (decreases) in the forward commodity price in isolation would result in significantly higher (lower) fair values for long positions (contracts that give Generation the obligation or option to purchase a commodity), with offsetting impacts to short positions (contracts that give Generation the obligation or right to sell a commodity). Increases (decreases) in volatility would increase (decrease) the value for the holder of the option (writer of the option). Generally, a change in the estimate of forward commodity prices is unrelated to a change in the estimate of volatility of prices. An increase to the reserves listed above would decrease the fair value of the positions. An increase to the heat rate or renewable factors would increase the fair value accordingly. Generally, interrelationships exist between market prices of natural gas and power. As such, an increase in natural gas pricing would potentially have a similar impact on forward power markets.

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	9 Months Ended
Commitments and Contingencies (All Registrants)	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (All Registrants)	Commitments and Contingencies (All Registrants) The following is an update to the current status of commitments and contingencies set forth in Note 19 — Commitments and Contingencies of the Exelon 2020 Form 10-K. Commitments PHI Merger Commitments (Exelon, PHI, Pepco, DPL, and ACE). Approval of the PHI Merger in Delaware, New Jersey, Maryland, and the District of Columbia was conditioned upon Exelon and PHI agreeing to certain commitments. The following amounts represent total commitment costs that have been recorded since the acquisition date and the total remaining obligations for Exelon, PHI, Pepco, DPL, and ACE as of September 30, 2021: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 74 62 51 7 4 __________ (a) Remaining commitments extend through 2026 and include rate credits, energy efficiency programs and delivery system modernization. In addition, Exelon is committed to develop or to assist in the commercial development of approximately 37 MWs of new solar generation in Maryland, District of Columbia, and Delaware at an estimated cost of approximately $135 million, which will generate future earnings at Exelon and Generation. Investment costs, which are expected to be primarily capital in nature, are recognized as incurred and recorded in Exelon's and Generation's financial statements. As of September 30, 2021, approximately 33 MWs of new generation were developed and Exelon and Generation have incurred costs of $121 million. Approximately 30 MWs of the new generation developed was part of Generation's first quarter 2021 sale of a significant portion of its solar business. Refer to Note 2 — Mergers, Acquisitions, and Dispositions for additional information on the solar business. Exelon has also committed to purchase 100 MWs of wind energy in PJM. DPL has committed to conducting three RFPs to procure up to a total of 120 MWs of wind RECs for the purpose of meeting Delaware's renewable portfolio standards. DPL has conducted two of the three wind REC RFPs. The first 40 MW wind REC tranche was conducted in 2017 and did not result in a purchase agreement. The second 40 MW wind REC tranche was conducted in 2018 and resulted in a proposed REC purchase agreement that was approved by the DPSC in 2019. The third and final 40 MW wind REC tranche will be conducted in 2022. Commercial Commitments (All Registrants). The Registrants’ commercial commitments as of September 30, 2021, representing commitments potentially triggered by future events were as follow s: Expiration within Total 2021 2022 2023 2024 2025 2026 and beyond Exelon Letters of credit $ 2,241 $ 268 $ 1,860 $ 113 $ — $ — $ — Surety bonds (a) 971 403 566 — 2 — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 31 — 3 3 6 6 13 Total commercial commitments $ 3,621 $ 671 $ 2,429 $ 116 $ 8 $ 6 $ 391 Generation Letters of credit $ 2,223 $ 264 $ 1,846 $ 113 $ — $ — $ — Surety bonds (a) 826 352 474 — — — — Total commercial commitments $ 3,049 $ 616 $ 2,320 $ 113 $ — $ — $ — ComEd Letters of credit $ 7 $ 2 $ 5 $ — $ — $ — $ — Surety bonds (a) 17 5 10 — 2 — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 224 $ 7 $ 15 $ — $ 2 $ — $ 200 PECO Letters of credit $ 1 $ — $ 1 $ — $ — $ — $ — Surety bonds (a) 2 — 2 — — — — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 181 $ — $ 3 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ — $ 2 $ — $ — $ — $ — Surety bonds (a) 3 2 1 — — — — Total commercial commitments $ 5 $ 2 $ 3 $ — $ — $ — $ — PHI Surety bonds (a) $ 23 $ 3 $ 20 $ — $ — $ — $ — Guaranteed lease residual values (b) 31 — 3 3 6 6 13 Total commercial commitments $ 54 $ 3 $ 23 $ 3 $ 6 $ 6 $ 13 Pepco Surety bonds (a) $ 14 $ — $ 14 $ — $ — $ — $ — Guaranteed lease residual values (b) 10 — 1 1 2 2 4 Total commercial commitments $ 24 $ — $ 15 $ 1 $ 2 $ 2 $ 4 DPL Surety bonds (a) $ 5 $ 2 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 13 — 1 1 3 3 5 Total commercial commitments $ 18 $ 2 $ 4 $ 1 $ 3 $ 3 $ 5 ACE Surety bonds (a) $ 4 $ 1 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 8 — 1 1 1 1 4 Total commercial commitments $ 12 $ 1 $ 4 $ 1 $ 1 $ 1 $ 4 __________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $75 million guaranteed by Exelon and PHI, of which $25 million, $32 million, and $18 million is guaranteed by Pepco, DPL, and ACE, respectively. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. Environmental Remediation Matters General (All Registrants). The Registrants’ operations have in the past, and may in the future, require substantial expenditures to comply with environmental laws. Additionally, under Federal and state environmental laws, the Registrants are generally liable for the costs of remediating environmental contamination of property now or formerly owned by them and of property contaminated by hazardous substances generated by them. The Registrants own or lease a number of real estate parcels, including parcels on which their operations or the operations of others may have resulted in contamination by substances that are considered hazardous under environmental laws. In addition, the Registrants are currently involved in a number of proceedings relating to sites where hazardous substances have been deposited and may be subject to additional proceedings in the future. Unless otherwise disclosed, the Registrants cannot reasonably estimate whether they will incur significant liabilities for additional investigation and remediation costs at these or additional sites identified by the Registrants, environmental agencies or others, or whether such costs will be recoverable from third parties, including customers. Additional costs could have a material, unfavorable impact on the Registrants' financial statements. MGP Sites (Exelon and the Utility Registrants). ComEd, PECO, BGE, and DPL have identified sites where former MGP or gas purification activities have or may have resulted in actual site contamination. For almost all of these sites, there are additional PRPs that may share responsibility for the ultimate remediation of each location. • ComEd has 21 sites that are currently under some degree of active study and/or remediation. ComEd expects the majority of the remediation at these sites to continue through at least 2027. • PECO has 6 sites that are currently under some degree of active study and/or remediation. PECO expects the majority of the remediation at these sites to continue through at least 2023. • BGE has 4 sites that currently require some level of remediation and/or ongoing activity. BGE expects the majority of the remediation at these sites to continue through at least 2023. • DPL has 1 site that is currently under study and the required cost at the site is not expected to be material. The historical nature of the MGP and gas purification sites and the fact that many of the sites have been buried and built over, impacts the ability to determine a precise estimate of the ultimate costs prior to initial sampling and determination of the exact scope and method of remedial activity. Management determines its best estimate of remediation costs using all available information at the time of each study, including probabilistic and deterministic modeling for ComEd and PECO, and the remediation standards currently required by the applicable state environmental agency. Prior to completion of any significant clean up, each site remediation plan is approved by the appropriate state environmental agency. ComEd, pursuant to an ICC order, and PECO, pursuant to settlements of natural gas distribution rate cases with the PAPUC, are currently recovering environmental remediation costs of former MGP facility sites through customer rates. While BGE and DPL do not have riders for MGP clean-up costs, they have historically received recovery of actual clean-up costs in distribution rates. As of September 30, 2021 and December 31, 2020, the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities in their respective Consolidated Balance Sheets: September 30, 2021 December 31, 2020 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 474 $ 310 $ 483 $ 314 Generation 119 — 121 — ComEd 284 284 293 293 PECO 23 21 23 21 BGE 6 5 2 — PHI 42 — 44 — Pepco 40 — 42 — DPL 1 — 1 — ACE 1 — 1 — Cotter Corporation (Exelon and Generation). The EPA has advised Cotter Corporation (Cotter), a former ComEd subsidiary, that it is potentially liable in connection with radiological contamination at a site known as the West Lake Landfill in Missouri. In 2000, ComEd sold Cotter to an unaffiliated third-party. As part of the sale, ComEd agreed to indemnify Cotter for any liability arising in connection with the West Lake Landfill. In connection with Exelon’s 2001 corporate restructuring, this responsibility to indemnify Cotter was transferred to Generation. Including Cotter, there are three PRPs participating in the West Lake Landfill remediation proceeding. Investigation by Generation has identified a number of other parties who also may be PRPs and could be liable to contribute to the final remedy. Further investigation is ongoing. In September 2018, the EPA issued its Record of Decision Amendment (RODA) for the selection of a final remedy. The RODA modified the remedy previously selected by EPA in its 2008 Record of Decision (ROD). While the ROD required only that the radiological materials and other wastes at the site be capped, the 2018 RODA requires partial excavation of the radiological materials in addition to the previously selected capping remedy. The RODA also allows for variation in depths of excavation depending on radiological concentrations. The EPA and the PRPs have entered into a Consent Agreement to perform the Remedial Design, which is expected to be completed in late 2024. In March 2019 the PRPs received Special Notice Letters from the EPA to perform the Remedial Action work. On October 8, 2019, Cotter (Generation’s indemnitee) provided a non-binding good faith offer to conduct, or finance, a portion of the remedy, subject to certain conditions. The total estimated cost of the remedy, taking into account the current EPA technical requirements and the total costs expected to be incurred collectively by the PRPs in fully executing the remedy, is approximately $290 million, including cost escalation on an undiscounted basis, which would be allocated among the final group of PRPs. Generation has determined that a loss associated with the EPA’s partial excavation and enhanced landfill cover remedy is probable and has recorded a liability included in the table above, that reflects management’s best estimate of Cotter’s allocable share of the ultimate cost. Given the joint and several nature of this liability, the magnitude of Generation’s ultimate liability will depend on the actual costs incurred to implement the required remedy as well as on the nature and terms of any cost-sharing arrangements with the final group of PRPs. Therefore, it is reasonably possible that the ultimate cost and Cotter's associated allocable share could differ significantly once these uncertainties are resolved, which could have a material impact in Exelon's and Generation's future financial statements. One of the other PRPs has indicated it will be making a contribution claim against Cotter for costs that it has incurred to prevent a subsurface fire from spreading to those areas of the West Lake Landfill where radiological materials are believed to have been disposed. At this time, Exelon and Generation do not possess sufficient information to assess this claim and therefore are unable to estimate a range of loss, if any. As such, no liability has been recorded for the potential contribution claim. It is reasonably possible, however, that resolution of this matter could have a material, unfavorable impact in Exelon’s and Generation's financial statements. In January 2018, the PRPs were advised by the EPA that it will begin an additional investigation and evaluation of groundwater conditions at the West Lake Landfill. In September 2018, the PRPs agreed to an Administrative Settlement Agreement and Order on Consent for the performance by the PRPs of the groundwater Remedial Investigation and Feasibility Study (RI/FS). The purpose of this RI/FS is to define the nature and extent of any groundwater contamination from the West Lake Landfill site and evaluate remedial alternatives. Generation estimates the undiscounted cost for the groundwater RI/FS to be approximately $40 million. Generation determined a loss associated with the RI/FS is probable and has recorded a liability included in the table above that reflects management’s best estimate of Cotter’s allocable share of the cost among the PRPs. At this time Generation cannot predict the likelihood or the extent to which, if any, remediation activities may be required and therefore cannot estimate a reasonably possible range of loss for response costs beyond those associated with the RI/FS component. It is reasonably possible, however, that resolution of this matter could have a material, unfavorable impact in Exelon’s and Generation’s future financial statements. In August 2011, Cotter was notified by the DOJ that Cotter is considered a PRP with respect to the government’s clean-up costs for contamination attributable to low level radioactive residues at a former storage and reprocessing facility named Latty Avenue near St. Louis, Missouri. The Latty Avenue site is included in ComEd’s (now Generation's) indemnification responsibilities discussed above as part of the sale of Cotter. The radioactive residues had been generated initially in connection with the processing of uranium ores as part of the U.S. Government’s Manhattan Project. Cotter purchased the residues in 1969 for initial processing at the Latty Avenue facility for the subsequent extraction of uranium and metals. In 1976, the NRC found that the Latty Avenue site had radiation levels exceeding NRC criteria for decontamination of land areas. Latty Avenue was investigated and remediated by the United States Army Corps of Engineers pursuant to funding under FUSRAP. Pursuant to a series of annual agreements since 2011, the DOJ and the PRPs have tolled the statute of limitations until February 28, 2022 so that settlement discussions can proceed. On August 3, 2020, the DOJ advised Cotter and the other PRPs that it is seeking approximately $90 million from all the PRPs and has directed that the PRPs must submit a good faith joint proposed settlement offer. At this time, the DOJ has stayed their request for a good faith offer while the parties review cost documentation associated with the cost claim. Generation has determined that a loss associated with this matter is probable under its indemnification agreement with Cotter and has recorded an estimated liability, which is included in the table above. Benning Road Site (Exelon, Generation, PHI, and Pepco) . In September 2010, PHI received a letter from EPA identifying the Benning Road site as one of six land-based sites potentially contributing to contamination of the lower Anacostia River. A portion of the site was formerly the location of a Pepco Energy Services electric generating facility, which was deactivated in June 2012. The remaining portion of the site consists of a Pepco transmission and distribution service center that remains in operation. In December 2011, the U.S. District Court for the District of Columbia approved a Consent Decree entered into by Pepco and Pepco Energy Services with the DOEE, which requires Pepco and Pepco Energy Services to conduct a RI/FS for the Benning Road site and an approximately 10 to 15-acre portion of the adjacent Anacostia River. Since 2013, Pepco and Pepco Energy Services (now Generation, pursuant to Exelon's 2016 acquisition of PHI) have been performing RI work and have submitted multiple draft RI reports to the DOEE. In September 2019, Pepco and Generation issued a draft “final” RI report which DOEE approved on February 3, 2020. Pepco and Generation are developing a FS to evaluate possible remedial alternatives for submission to DOEE. The Court has established a schedule for completion of the FS, and approval by the DOEE, by March 16, 2022. After completion and approval of the FS, DOEE will prepare a Proposed Plan for public comment and then issue a ROD identifying any further response actions determined to be necessary. PHI, Pepco, and Generation have determined that a loss associated with this matter is probable and have accrued an estimated liability, which is included in the table above. Anacostia River Tidal Reach (Exelon, PHI, and Pepco) . Contemporaneous with the Benning Road site RI/FS being performed by Pepco and Generation, DOEE and NPS have been conducting a separate RI/FS focused on the entire tidal reach of the Anacostia River extending from just north of the Maryland-District of Columbia boundary line to the confluence of the Anacostia and Potomac Rivers. The river-wide RI incorporated the results of the river sampling performed by Pepco and Pepco Energy Services as part of the Benning RI/FS, as well as similar sampling efforts conducted by owners of other sites adjacent to this segment of the river and supplemental river sampling conducted by DOEE’s contractor. In April 2018, DOEE released a draft RI report for public review and comment. Pepco submitted written comments to the draft RI and participated in a public hearing. Pepco has determined that it is probable that costs for remediation will be incurred and recorded a liability in the third quarter 2019 for management’s best estimate of its share of those costs. On September 30, 2020, DOEE released its Interim ROD. The Interim ROD reflects an adaptive management approach which will require several identified “hot spots” in the river to be addressed first while continuing to conduct studies and to monitor the river to evaluate improvements and determine potential future remediation plans. The adaptive management process chosen by DOEE is less intrusive, provides more long-term environmental certainty, is less costly, and allows for site specific remediation plans already underway, including the plan for the Benning Road site to proceed to conclusion. Pepco concluded that incremental exposure remains reasonably possible, but management cannot reasonably estimate a range of loss beyond the amounts recorded, which are included in the table above. On July 12, 2021, DOEE and NPS held a virtual meeting with the PRP's in response to a General Notice Letter sent by each agency inviting the PRP's to participate in discussions, which PEPCO attended. In addition to the activities associated with the remedial process outlined above, CERCLA separately requires federal and state (here including Washington, D.C.) Natural Resource Trustees (federal or state agencies designated by the President or the relevant state, respectively, or Indian tribes) to conduct an assessment of any damages to natural resources within their jurisdiction as a result of the contamination that is being remediated. The Trustees can seek compensation from responsible parties for such damages, including restoration costs. During the second quarter of 2018, Pepco became aware that the Trustees are in the beginning stages of a Natural Resources Damages (NRD) assessment, a process that often takes many years beyond the remedial decision to complete. Pepco has concluded that a loss associated with the eventual NRD assessment is reasonably possible. Due to the very early stage of the assessment process, Pepco cannot reasonably estimate the range of loss. Litigation and Regulatory Matters Asbestos Personal Injury Claims (Exelon and Generation). Generation maintains a reserve for claims associated with asbestos-related personal injury actions in certain facilities that are currently owned by Generation or were previously owned by ComEd and PECO. The estimated liabilities are recorded on an undiscounted basis and exclude the estimated legal costs associated with handling these matters, which could be material. At September 30, 2021 and December 31, 2020, Exelon and Generation had recorded estimated liabilities of approximately $82 million and $89 million, respectively, in total for asbestos-related bodily injury claims. As of September 30, 2021, approximately $19 million of this amount related to 211 open claims presented to Generation, while the remaining $63 million is for estimated future asbestos-related bodily injury claims anticipated to arise through 2055, based on actuarial assumptions and analyses, which are updated on an annual basis. On a quarterly basis, Generation monitors actual experience against the number of forecasted claims to be received and expected claim payments and evaluates whether adjustments to the estimated liabilities are necessary. It is reasonably possible that additional exposure to estimated future asbestos-related bodily injury claims in excess of the amount accrued could have a material, unfavorable impact in Exelon’s and Generation’s financial statements. However, management cannot reasonably estimate a range of loss beyond the amounts recorded. Deferred Prosecution Agreement (DPA) and Related Matters (Exelon and ComEd). Exelon and ComEd received a grand jury subpoena in the second quarter of 2019 from the U.S. Attorney’s Office for the Northern District of Illinois (USAO) requiring production of information concerning their lobbying activities in the State of Illinois. On October 4, 2019, Exelon and ComEd received a second grand jury subpoena from the USAO requiring production of records of any communications with certain individuals and entities. On October 22, 2019, the SEC notified Exelon and ComEd that it had also opened an investigation into their lobbying activities. On July 17, 2020, ComEd entered into a DPA with the USAO to resolve the USAO investigation. Under the DPA, the USAO filed a single charge alleging that ComEd improperly gave and offered to give jobs, vendor subcontracts, and payments associated with those jobs and subcontracts for the benefit of the Speaker of the Illinois House of Representatives and the Speaker’s associates, with the intent to influence the Speaker’s action regarding legislation affecting ComEd’s interests. The DPA provides that the USAO will defer any prosecution of such charge and any other criminal or civil case against ComEd in connection with the matters identified therein for a three-year period subject to certain obligations of ComEd, including payment to the U.S. Treasury of $200 million, which was paid in November 2020. Exelon was not made a party to the DPA, and therefore the investigation by the USAO into Exelon’s activities ended with no charges being brought against Exelon. The SEC’s investigation remains ongoing and Exelon and ComEd have cooperated fully and intend to continue to cooperate fully with the SEC. Exelon and ComEd cannot predict the outcome of the SEC investigation. No loss contingency has been reflected in Exelon's and ComEd's consolidated financial statements with respect to the SEC investigation, as this contingency is neither probable nor reasonably estimable at this time. Subsequent to Exelon announcing the receipt of the subpoenas, various lawsuits were filed, and various demand letters were received related to the subject of the subpoenas, the conduct described in the DPA and the SEC's investigation, including: • Four putative class action lawsuits against ComEd and Exelon were filed in federal court in the third quarter of 2020 alleging, among other things, civil violations of federal racketeering laws. In addition, the Citizens Utility Board (CUB) filed a motion to intervene in these cases on October 22, 2020 which was granted on December 23, 2020. On December 2, 2020, the court appointed interim lead plaintiffs in the federal cases which consisted of counsel for three of the four federal cases. These plaintiffs filed a consolidated complaint on January 5, 2021. CUB also filed its own complaint against ComEd only on the same day. The remaining federal case, Potter, et al. v. Exelon et al, differed from the other lawsuits as it named additional individual defendants not named in the consolidated complaint. However, the Potter plaintiffs voluntarily dismissed their complaint without prejudice on April 5, 2021. ComEd and Exelon moved to dismiss the consolidated class action complaint and CUB’s complaint on February 4, 2021 and briefing was completed on March 22, 2021. On March 25, 2021, the parties agreed, along with state court plaintiffs, discussed below, to jointly engage in mediation. The parties participated in a one-day mediation on June 7, 2021 but no settlement was reached. On September 9, 2021, the federal court granted Exelon’s and ComEd’s motion to dismiss and dismissed the plaintiffs’ and CUB’s federal law claim with prejudice. The federal court also dismissed the related state law claims made by the federal plaintiffs and CUB on jurisdictional grounds. Plaintiffs have appealed the ruling to the Seventh Circuit Court of Appeals. Plaintiffs' opening appeal brief is due January 14, 2022, Exelon's and ComEd's response brief is due February 14, 2022, and Plaintiffs' reply brief is due March 7, 2022. Plaintiffs also refiled their state law claims in state court and have moved to consolidate that action with the already pending consumer state court class action, discussed below. CUB also refiled its state law claims in state court. • Three putative class action lawsuits against ComEd and Exelon were filed in Illinois state court in the third quarter of 2020 seeking restitution and compensatory damages on behalf of ComEd customers. The cases were consolidated into a single action in October of 2020. In November 2020, CUB filed a motion to intervene in the cases pursuant to an Illinois statute allowing CUB to intervene as a party or otherwise participate on behalf of utility consumers in any proceeding which affects the interest of utility consumers. On November 23, 2020, the court allowed CUB’s intervention, but denied its request to stay these cases. Plaintiffs subsequently filed a consolidated complaint, and ComEd and Exelon filed a motion to dismiss on jurisdictional and substantive grounds on January 11, 2021. Briefing on that motion was completed on March 2, 2021. The parties agreed, on March 25, 2021, along with the federal court plaintiffs discussed above, to jointly engage in mediation. The parties participated in a one-day mediation on June 7, 2021 but no settlement was reached. Oral argument on the state court pending motion to dismiss was held on August 4, 2021. On September 27, 2021, the court set a tentative ruling date on the motion to dismiss for November 30, 2021. It is unclear at this time what impact the recent filings by the federal court plaintiffs and CUB will have on this action and the pending motion to dismiss. • A putative class action lawsuit against Exelon and certain officers of Exelon and ComEd was filed in federal court in December 2019 alleging misrepresentations and omissions in Exelon’s SEC filings related to ComEd’s lobbying activities and the related investigations. The complaint was amended on September 16, 2020, to dismiss two of the original defendants and add other defendants, including ComEd. Defendants filed a motion to dismiss in November 2020. The court denied the motion in April 2021. On May 26, 2021, defendants moved the court to certify its order denying the motion to dismiss for interlocutory appeal. Briefing on the motion was completed in June 2021 and the motion remains pending. Litigation has proceeded and in May 2021, the parties each filed respective initial discovery disclosures. On June 9, 2021, defendants filed their answer and affirmative defenses to the complaint. The parties are currently engaged in discovery; however, on September 9, 2021, the U.S. government moved to intervene in this lawsuit and stay discovery relating to the U.S. government’s ongoing criminal proceedings until the parties to the litigation agree to an acceptable protective order. The court granted the U.S. government’s motion on September 23, 2021 and discovery remains stayed until further order of the court. • Five shareholders sent letters to the Exelon Board of Directors between 2020 and 2021 demanding, among other things, that the Exelon Board of Directors investigate and address alleged breaches of fiduciary duties and other alleged violations by Exelon and ComEd officers and directors related to the conduct described in the DPA. In the first quarter of 2021, the Exelon Board of Directors appointed a Special Litigation Committee (“SLC”) consisting of disinterested and independent parties to investigate and address these shareholders’ allegations and make recommendations to the Exelon Board of Directors based on the outcome of the SLC’s investigation. In July 2021, one of the demand letter shareholders filed a derivative action against current and former Exelon and ComEd officers and directors, and against Exelon, as nominal defendant, asserting the same claims made in its demand letter. On October 12, 2021, the parties to the derivative action filed an agreed motion to stay that litigation for 120 days in order to allow the SLC to continue its investigation, which the court granted. The parties will confer in advance of the 120-day deadline to determine whether the stay should be extended. • A separate shareholder demand seeking a review of certain Exelon books and records was received in August 2021. Exelon is in the process of responding to this demand. No loss contingencies have been reflec ted in Exelon’s and ComEd’s consolidated financial statements with respect to these matters, as such contingencies are neither probable nor reasonably estimable at this time. On August 12, 2021, the ICC commenced a proceeding, under its general regulatory authority, to investigate whether the conduct described in the DPA resulted in ComEd’s recovery, through rates, of costs that were not properly recoverable under law and, if so, what remedial action should be taken. The Staff Report cited by the ICC in its initiating order expressed “concerns” about whether ComEd improperly recovered DPA-related costs from customers. The Illinois Attorney General and CUB have intervened in the proceeding. Counsel for plaintiffs in the putative consumer class actions pending in Illinois Circuit Court have also sought to “partially” intervene, which request is pending. On October 14, 2021, as required by provisions of the Clean Energy Law, the ICC initiated a separate docket to investigate the rate treatment of costs associated with the DPA, including the fine paid by ComEd, and whether ComEd “collected, spent, allocated, transferred, remitted, or caused in any other way to be expended ratepayer funds that were not lawfully recoverable through rates, and which should accordingly be refunded to ratepayers ….” That proceeding must be completed within 330 days. On October 19, 2021, the ICC moved to consolidate these two proceedings because they address "similar issues and facts." That motion is pending. No schedule has been set for submission of testimony or for an evidentiary hearing in either docket. A status hearing is set in both matters for November 4, 2021. Exelon and ComEd cannot predict the outcome of these proceedings. Impacts of the February 2021 Extreme Cold Weather Event and Texas-based Generating Assets Outages (Exelon and Generation). Beginning on February 15, 2021, Generation’s Texas-based generating assets within the ERCOT market, specifically Colorado Bend II, Wolf Hollow II, and Handley, experienced outages as a result of extreme cold weather conditions. In addition, those weather conditions drove increased demand for service, dramatically increased wholesale power prices, and also increased gas prices in certain regions. See Note 3 — Regulatory Matters for additional inform

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon)	9 Months Ended
Changes in Accumulated Other Comprehensive Income (Exelon)	Sep. 30, 2021
Changes in Accumulated Other Comprehensive Income [Abstract]
Changes in Accumulated Other Comprehensive Income [Text Block]	Changes in Accumulated Other Comprehensive Income (Exelon) The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended September 30, 2021 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (5) $ (3,264) $ (20) $ (3,289) OCI before reclassifications — 14 (3) 11 Amounts reclassified from AOCI — 55 — 55 Net current-period OCI — 69 (3) 66 Ending balance $ (5) $ (3,195) $ (23) $ (3,223) Three Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (3) $ (3,096) $ (33) $ (3,132) OCI before reclassifications (1) (13) 3 (11) Amounts reclassified from AOCI — 39 — 39 Net current-period OCI (1) 26 3 28 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Nine Months Ended September 30, 2021 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (5) $ (3,372) $ (23) $ (3,400) OCI before reclassifications (1) 15 — 14 Amounts reclassified from AOCI — 163 — 163 Net current-period OCI (1) 178 — 177 Ending balance $ (6) $ (3,194) $ (23) $ (3,223) Nine Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (2) $ (3,165) $ (27) $ (3,194) OCI before reclassifications (2) (17) (3) (22) Amounts reclassified from AOCI — 112 — 112 Net current-period OCI (2) 95 (3) 90 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) ______ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 11 — Retirement Benefits for additional information. See Exelon's Statements of Operations and Comprehensive Income for individual components of AOCI. The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 1 $ 4 $ 3 $ 12 Actuarial loss reclassified to periodic benefit cost (19) (16) (57) (50) Pension and non-pension postretirement benefit plans valuation adjustment (7) 3 (8) 6

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, PHI and ACE)	9 Months Ended
	Sep. 30, 2021
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure	Variable Interest Entities (Exelon, Generation, PHI, and ACE) At September 30, 2021 and December 31, 2020, Exelon, Generation, PHI, and ACE collectively consolidated several VIEs or VIE groups for which the applicable Registrant was the primary beneficiary (see Consolidated VIEs below) and had significant interests in several other VIEs for which the applicable Registrant does not have the power to direct the entities’ activities and, accordingly, was not the primary beneficiary (see Unconsolidated VIEs below). Consolidated and unconsolidated VIEs are aggregated to the extent that the entities have similar risk profiles. Consolidated VIEs The table below shows the carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the consolidated financial statements of Exelon, Generation, PHI, and ACE as of September 30, 2021 and December 31, 2020. The assets, except as noted in the footnotes to the table below, can only be used to settle obligations of the VIEs. The liabilities, except as noted in the footnote to the table below, are such that creditors, or beneficiaries, do not have recourse to the general credit of Exelon, Generation, PHI, and ACE. September 30, 2021 December 31, 2020 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 38 $ 38 $ — $ — $ 98 $ 98 $ — $ — Restricted cash and cash equivalents 47 42 5 5 47 44 3 3 Accounts receivable Customer 25 25 — — 148 148 — — Other 7 7 — — 36 36 — — Unamortized energy contract assets 21 21 — — 22 22 — — Inventories, net Materials and supplies 14 14 — — 244 244 — — Assets held for sale (b) — — — — 101 101 — — Other current assets 517 513 4 — 674 669 5 — Total current assets 669 660 9 5 1,370 1,362 8 3 Property, plant, and equipment, net 2,052 2,052 — — 5,803 5,803 — — Nuclear decommissioning trust funds — — — — 3,007 3,007 — — Unamortized energy contract assets 210 210 — — 249 249 — — Other noncurrent assets 22 13 9 9 52 42 10 10 Total noncurrent assets 2,284 2,275 9 9 9,111 9,101 10 10 Total assets (c) $ 2,953 $ 2,935 $ 18 $ 14 $ 10,481 $ 10,463 $ 18 $ 13 Long-term debt due within one year $ 80 $ 70 $ 10 $ 6 $ 94 $ 68 $ 26 $ 21 Accounts payable 11 11 — — 81 81 — — Accrued expenses 14 14 — — 70 70 — — Unamortized energy contract liabilities — — — — 4 4 — — Liabilities held for sale (b) — — — — 16 16 — — Other current liabilities — — — — 5 5 — — Total current liabilities 105 95 10 6 270 244 26 21 Long-term debt 832 832 — — 889 889 — — Asset retirement obligations 149 149 — — 2,318 2,318 — — Other noncurrent liabilities 3 3 — — 129 129 — — Total noncurrent liabilities 984 984 — — 3,336 3,336 — — Total liabilities (d) $ 1,089 $ 1,079 $ 10 $ 6 $ 3,606 $ 3,580 $ 26 $ 21 _________ (a) Includes certain purchase accounting adjustments from the PHI merger not pushed down to ACE. (b) In the fourth quarter of 2020, Generation entered into an agreement for the sale of a significant portion of Generation's solar business, and as a result of this transaction, Exelon and Generation reclassified the consolidated VIEs' solar assets and liabilities as held for sale. Completion of the transaction occurred in the first quarter of 2021. Refer to Note 2 — Mergers, Acquisitions, and Dispositions for additional information on the solar business. (c) Exelon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $21 million and $22 million, non-current unamortized energy contract assets of $210 million and $249 million, assets held for sale of $0 million and $9 million, and other unrestricted assets of $0 million and $1 million as of September 30, 2021 and December 31, 2020, respectively. (d) Exelon’s and Generation’s balances include liabilities with recourse of $1 million and $8 million as of September 30, 2021 and December 31, 2020, respectively. As of September 30, 2021 and December 31, 2020, Exelon's and Generation's consolidated VIEs included the following: Consolidated VIE or VIE groups: Reason entity is a VIE: Reason Generation is primary beneficiary: CENG - A joint venture between Generation and EDF. Generation had a 50.01% equity ownership in CENG as of December 31, 2020 and acquired EDF's 49.99% equity interest on August 6,2021 resulting in CENG no longer being classified as a consolidated VIE beginning in the third quarter of 2021. See additional discussion below. Disproportionate relationship between equity interest and operational control as a result of the NOSA described further below. Generation conducts the operational activities. EGRP - A collection of wind and solar project entities. Generation has a 51% equity ownership in EGRP. See additional discussion below. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. Bluestem Wind Energy Holdings, LLC - A Tax Equity structure which is consolidated by EGRP. Generation has a noncontrolling interest. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. Antelope Valley - A solar generating facility, which is 100% owned by Generation. Antelope Valley sells all of its output to PG&E through a PPA. The PPA contract absorbs variability through a performance guarantee. Generation conducts all activities. Equity investment in distributed energy company - Generation has a 31% equity ownership. This distributed energy company has an interest in an unconsolidated VIE. (See Unconsolidated VIEs disclosure below). Generation fully impaired this investment in 2019. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. NER - A bankruptcy remote, special purpose entity which is 100% owned by Generation, which purchases certain of Generation’s customer accounts receivable arising from the sale of retail electricity. NER’s assets will be available first and foremost to satisfy the claims of the creditors of NER. See Note 6 - Accounts Receivable for additional information on the sale of receivables. Equity capitalization is insufficient to support its operations. Generation conducts all activities. CENG - On April 1, 2014, Generation, CENG, and subsidiaries of CENG executed the NOSA pursuant to which Generation conducts all activities associated with the operations of the CENG fleet and provides corporate and administrative services to CENG and the CENG fleet for the remaining life of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to the CENG member rights of EDF. On November 20, 2019, Generation received notice of EDF's intention to exercise the put option to sell its 49.99% equity interest in CENG to Generation and the put automatically exercised on January 19, 2020. On August 6, 2021, Generation and EDF entered into a settlement agreement pursuant to which Generation purchased EDF's equity interest in CENG and resulted in CENG no longer being classified as a consolidated VIE beginning in the third quarter of 2021. Refer to Note 2 — Mergers, Acquisitions, and Dispositions for additional information. Exelon and Generation, where indicated, provide the following support to CENG: • Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF against third-party claims that may arise from any future nuclear incident (as defined in the Price-Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this Indemnity Agreement. See Note 19 — Commitments and Contingencies of the Exelon 2020 Form 10-K for more details. • Exelon has executed an agreement to provide up to $245 million to support the operations of CENG as well as a $165 million guarantee of CENG’s cash pooling agreement with its subsidiaries. Prior to August 6, 2021, Generation and EDF shared in the $688 million of contingent payment obligations for the payment of contingent retrospective premium adjustments for the nuclear liability insurance. Following the execution of the settlement agreement, EDF no longer shares in the obligation. EGRP - EGRP is a collection of wind and solar project entities and some of these project entities are VIEs that are consolidated by EGRP. Generation owns a number of limited liability companies that build, own, and operate solar and wind power facilities some of which are owned by EGRP. While Generation or EGRP owns 100% of the solar entities and 100% of the majority of the wind entities, it has been determined that certain of the solar and wind entities are VIEs because the entities require additional subordinated financial support in the form of a parental guarantee of debt, loans from the customers in order to obtain the necessary funds for construction of the solar facilities, or the customers absorb price variability from the entities through the fixed price power and/or REC purchase agreements. Generation is the primary beneficiary of these solar and wind entities that qualify as VIEs because Generation controls the design, construction, and operation of the facilities. There is limited recourse to Generation related to certain solar and wind entities. In 2017, Generation’s interests in EGRP were contributed to and are pledged for the ExGen Renewables IV non-recourse debt project financing structure. Refer to Note 17 — Debt and Credit Agreements of the Exelon 2020 Form 10-K for additional information on ExGen Renewables IV. As of September 30, 2021 and December 31, 2020, Exelon's, PHI's, and ACE's consolidated VIE consists of: Consolidated VIEs: Reason entity is a VIE: Reason ACE is the primary beneficiary: ACE Funding - A special purpose entity formed by ACE for the purpose of securitizing authorized portions of ACE’s recoverable stranded costs through the issuance and sale of Transition Bonds. Proceeds from the sale of each series of Transition Bonds by ATF were transferred to ACE in exchange for the transfer by ACE to ATF of the right to collect a non-bypassable Transition Bond Charge from ACE customers pursuant to bondable stranded costs rate orders issued by the NJBPU in an amount sufficient to fund the principal and interest payments on Transition Bonds and related taxes, expenses and fees. ACE’s equity investment is a variable interest as, by design, it absorbs any initial variability of ATF. The bondholders also have a variable interest for the investment made to purchase the Transition Bonds. ACE controls the servicing activities. Unconsolidated VIEs Exelon’s and Generation’s variable interests in unconsolidated VIEs generally include equity investments and energy purchase and sale contracts. For the equity investments, the carrying amount of the investments is reflected in Exelon’s and Generation’s Consolidated Balance Sheets in Investments. For the energy purchase and sale contracts (commercial agreements), the carrying amount of assets and liabilities in Exelon’s and Generation’s Consolidated Balance Sheets that relate to their involvement with the VIEs are predominately related to working capital accounts and generally represent the amounts owed by, or owed to, Exelon and Generation for the deliveries associated with the current billing cycles under the commercial agreements. As of September 30, 2021 and December 31, 2020, Exelon and Generation had significant unconsolidated variable interests in several VIEs for which Exelon or Generation, as applicable, was not the primary beneficiary. These interests include certain equity method investments and certain commercial agreements. The following table presents summary information about Exelon's and Generation’s significant unconsolidated VIE entities: September 30, 2021 December 31, 2020 Commercial Equity Total Commercial Equity Total Total assets (a) $ 781 $ 370 $ 1,151 $ 777 $ 401 $ 1,178 Total liabilities (a) 80 209 289 61 223 284 Exelon's ownership interest in VIE (a) — 143 143 — 157 157 Other ownership interests in VIE (a) 701 18 719 716 21 737 _________ (a) These items represent amounts in the unconsolidated VIE balance sheets, not in Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. Exelon and Generation do not have any exposure to loss as they do not have a carrying amount in the equity investment VIEs as of September 30, 2021 and December 31, 2020. As of September 30, 2021 and December 31, 2020, Exelon's and Generation's unconsolidated VIEs consist of: Unconsolidated VIE groups: Reason entity is a VIE: Reason Generation is not the primary beneficiary: Equity investments in distributed energy companies - 1) Generation has a 90% equity ownership in a distributed energy company. 2) Generation, via a consolidated VIE, has a 90% equity ownership in another distributed energy company (See Consolidated VIEs disclosure above). Generation fully impaired this investment in 2019. Similar structures to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation does not conduct the operational activities. Energy Purchase and Sale agreements - Generation has several energy purchase and sale agreements with generating facilities. PPA contracts that absorb variability through fixed pricing. Generation does not conduct the operational activities.

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	9 Months Ended
Supplemental Financial Information (All Registrants)	Sep. 30, 2021
Supplemental Financial Information [Abstract]
Supplemental Financial Information (All Registrants)	Supplemental Financial Information (All Registrants) Supplemental Statement of Operations Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Operations and Comprehensive Income. Operating revenues Exelon Generation PHI DPL Three Months Ended September 30, 2021 Operating lease income $ 30 $ 29 $ 1 $ 1 Variable lease income 71 71 — — Three Months Ended September 30, 2020 Operating lease income $ 30 $ 28 $ 1 $ 1 Variable lease income 76 76 — — Nine Months Ended September 30, 2021 Operating lease income $ 47 $ 44 $ 3 $ 3 Variable lease income 208 207 1 1 Nine Months Ended September 30, 2020 Operating lease income $ 48 $ 43 $ 3 $ 3 Variable lease income 225 224 1 1 Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2021 Utility taxes (a) $ 242 $ 27 $ 67 $ 41 $ 21 $ 86 $ 80 $ 6 $ — Property 165 66 13 5 46 34 23 10 1 Payroll 57 26 7 4 5 7 2 1 1 Three Months Ended September 30, 2020 Utility taxes (a) $ 237 $ 26 $ 66 $ 41 $ 21 $ 83 $ 77 $ 5 $ 1 Property 152 66 7 4 42 32 21 10 1 Payroll 59 29 7 4 4 6 2 1 1 Nine Months Ended September 30, 2021 Utility taxes (a) $ 665 $ 73 $ 188 $ 107 $ 66 $ 231 $ 212 $ 17 $ 2 Property 470 199 30 13 131 97 65 30 2 Payroll 180 83 20 12 14 21 5 4 2 Nine Months Ended September 30, 2020 Utility taxes (a) $ 651 $ 75 $ 181 $ 102 $ 65 $ 228 $ 210 $ 16 $ 2 Property 449 199 23 12 121 94 63 29 2 Payroll 183 88 21 12 13 21 6 4 3 __________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 263 $ 263 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 102 102 — — — — — — — Net unrealized losses on NDT funds Regulatory Agreement Units (195) (195) — — — — — — — Non-Regulatory Agreement Units (88) (88) — — — — — — — Regulatory offset to NDT fund-related activities (b) (38) (38) — — — — — — — Decommissioning-related activities 44 44 — — — — — — — AFUDC — Equity 36 — 10 7 7 12 9 2 1 Non-service net periodic benefit cost 19 — — — — — — — — Net unrealized losses from equity investments (c) (179) (179) — — — — — — — Three Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 50 $ 50 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 23 23 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 398 398 — — — — — — — Non-Regulatory Agreement Units 254 254 — — — — — — — Regulatory offset to NDT fund-related activities (b) (359) (359) — — — — — — — Decommissioning-related activities 366 366 — — — — — — — AFUDC — Equity 27 — 7 5 6 9 7 1 1 Non-service net periodic benefit cost 15 — — — — — — — — Other, net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 698 $ 698 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 392 392 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 84 84 — — — — — — — Non-Regulatory Agreement Units 38 38 — — — — — — — Regulatory offset to NDT fund-related activities (b) (607) (607) — — — — — — — Decommissioning-related activities 605 605 — — — — — — — AFUDC — Equity 99 — 23 19 21 36 30 4 2 Non-service net periodic benefit cost 64 — — — — — — — — Net unrealized losses from equity investments (c) (83) (83) — — — — — — — Nine Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 127 $ 127 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 127 127 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 111 111 — — — — — — — Non-Regulatory Agreement Units 1 1 — — — — — — — Regulatory offset to NDT fund-related activities (b) (192) (192) — — — — — — — Decommissioning-related activities 174 174 — — — — — — — AFUDC — Equity 76 — 22 12 16 26 20 3 3 Non-service net periodic benefit cost 38 — — — — — — — — __________ (a) Realized income includes interest, dividends and realized gains and losses on sales of NDT fund investments. (b) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units except for decommissioning-related impacts that were not offset for the Byron units starting in the second quarter of 2021, including the elimination of income taxes related to all NDT fund activity for those units. With Generation's September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning and Note 8 — Nuclear Decommissioning for additional information on the contractual offset suspension for the Byron units. (c) Net unrealized losses from equity investments that became publicly traded entities in the fourth quarter of 2020 and the first half of 2021. Supplemental Cash Flow Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Cash Flows. Depreciation, amortization, and accretion Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Property, plant, and equipment (a) $ 4,505 $ 2,698 $ 721 $ 249 $ 324 $ 467 $ 204 $ 126 $ 115 Amortization of regulatory assets (a) 439 — 172 10 110 147 98 31 18 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 23 23 — — — — — — — Nuclear fuel (c) 810 810 — — — — — — — ARO accretion (d) 383 383 — — — — — — — Total depreciation, amortization, and accretion $ 6,204 $ 3,951 $ 893 $ 259 $ 434 $ 614 $ 302 $ 157 $ 133 Nine Months Ended September 30, 2020 Property, plant, and equipment (a) $ 2,831 $ 1,121 $ 689 $ 238 $ 293 $ 436 $ 191 $ 116 $ 104 Amortization of regulatory assets (a) 434 — 152 21 112 149 91 27 30 Amortization of intangible assets, net (a) 47 40 — — — — — — — Amortization of energy contract assets and liabilities (b) 24 22 — — — — — — — Nuclear fuel (c) 708 708 — — — — — — — ARO accretion (d) 375 375 — — — — — — — Total depreciation, amortization, and accretion $ 4,419 $ 2,266 $ 841 $ 259 $ 405 $ 585 $ 282 $ 143 $ 134 __________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Pension and non-pension postretirement benefit costs $ 304 $ 92 $ 97 $ 5 $ 45 $ 36 $ 5 $ 2 $ 8 Allowance for credit losses 155 59 34 36 7 18 9 3 6 Other decommissioning-related activity (a) (810) (810) — — — — — — — Energy-related options (b) 45 45 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) (129) — (32) (20) 17 (94) (54) (17) (23) Severance costs (67) (75) 1 — — 1 — — — Long-term incentive plan 94 — — — — — — — — Amortization of operating ROU asset 146 98 2 — 22 21 5 7 3 AFUDC — Equity (99) — (23) (19) (21) (36) (30) (4) (2) Nine Months Ended September 30, 2020 Pension and non-pension postretirement benefit costs $ 310 $ 89 $ 85 $ 4 $ 46 $ 52 $ 11 $ 6 $ 10 Allowance for credit losses 130 16 23 38 12 41 24 15 2 Other decommissioning-related activity (a) (301) (301) — — — — — — — Energy-related options (b) 79 79 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) 66 — 51 (10) 10 15 (20) 15 20 Severance costs 96 88 1 — — — — — — Provision for excess and obsolete inventory 119 118 1 1 — (1) — (1) — Long-term incentive plan (8) — — — — — — — — Amortization of operating ROU asset 185 135 1 — 23 21 5 6 2 Deferred Prosecution Agreement payments (d) 200 — 200 — — — — — — AFUDC — Equity (76) — (22) (12) (16) (26) (20) (3) (3) __________ (a) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units except for decommissioning-related impacts that were not offset for the Byron units starting in the second quarter of 2021, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income, and income taxes related to all NDT fund activity for these units. With Generation's September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning and Note 8 — Nuclear Decommissioning for additional information on the contractual offset suspension for the Byron units. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution, energy efficiency, distributed generation, and transmission formula rates. For BGE, Pepco, DPL, and ACE, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO, reflects the change in regulatory assets and liabilities associated with its transmission formula rates. See Note 3 — Regulatory Matters for additional information. (d) See Note 15 — Commitments and Contingencies for additional information related to the Deferred Prosecution Agreement. The following tables provide a reconciliation of cash, cash equivalents, and restricted cash reported within the Registrants’ Consolidated Balance Sheets that sum to the total of the same amounts in their Consolidated Statements of Cash Flows. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 Cash and cash equivalents $ 2,957 $ 1,957 $ 241 $ 344 $ 225 $ 82 $ 19 $ 13 $ 16 Restricted cash and cash equivalents 473 62 276 8 27 71 41 26 5 Restricted cash included in other long-term assets 54 — 44 — — 9 — — 9 Total cash, restricted cash, and cash equivalents $ 3,484 $ 2,019 $ 561 $ 352 $ 252 $ 162 $ 60 $ 39 $ 30 December 31, 2020 Cash and cash equivalents $ 663 $ 226 $ 83 $ 19 $ 144 $ 111 $ 30 $ 15 $ 17 Restricted cash and cash equivalents 438 89 279 7 1 39 35 — 3 Restricted cash included in other long-term assets 53 — 43 — — 10 — — 10 Cash, restricted cash, and cash equivalents - Held for Sale 12 12 — — — — — — — Total cash, restricted cash, and cash equivalents $ 1,166 $ 327 $ 405 $ 26 $ 145 $ 160 $ 65 $ 15 $ 30 September 30, 2020 Cash and cash equivalents $ 1,858 $ 623 $ 76 $ 242 $ 326 $ 196 $ 125 $ 26 $ 13 Restricted cash and cash equivalents 485 100 305 7 1 38 33 — 4 Restricted cash included in other long-term assets 137 — 127 — — 10 — — 10 Total cash, restricted cash, and cash equivalents $ 2,480 $ 723 $ 508 $ 249 $ 327 $ 244 $ 158 $ 26 $ 27 December 31, 2019 Cash and cash equivalents $ 587 $ 303 $ 90 $ 21 $ 24 $ 131 $ 30 $ 13 $ 12 Restricted cash and cash equivalents 358 146 150 6 1 36 33 — 2 Restricted cash included in other long-term assets 177 — 163 — — 14 — — 14 Total cash, restricted cash, and cash equivalents $ 1,122 $ 449 $ 403 $ 27 $ 25 $ 181 $ 63 $ 13 $ 28 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2020 Form 10-K. Supplemental Balance Sheet Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 Compensation-related accruals (a) $ 894 $ 318 $ 148 $ 66 $ 72 $ 108 $ 34 $ 21 $ 16 Taxes accrued 508 222 80 61 90 98 67 16 7 Interest accrued 415 77 65 36 39 75 37 20 15 December 31, 2020 Compensation-related accruals (a) $ 1,069 $ 426 $ 170 $ 73 $ 84 $ 109 $ 36 $ 18 $ 17 Taxes accrued 527 229 94 16 73 117 90 18 12 Interest accrued 331 44 109 37 46 51 26 7 12 __________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation, and benefits.

Related Party Transactions (All

Related Party Transactions (All Registrants)	9 Months Ended
Related Party Transactions (All Registrants)	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions (All Registrants)	Related Party Transactions (All Registrants) Operating revenues from affiliates Generation The following table presents Generation’s Operating revenues from affiliates, which are primarily recorded as Purchased power from affiliates and an immaterial amount recorded as Operating and maintenance expense from affiliates at the Utility Registrants: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Operating revenues from affiliates: ComEd (a)(b) $ 96 $ 71 $ 249 $ 241 PECO (c) 59 68 142 146 BGE (d) 65 84 195 252 PHI 99 105 276 288 Pepco (e) 69 80 199 219 DPL (f) 25 21 63 60 ACE (g) 5 4 14 9 Other 5 3 10 5 Total operating revenues from affiliates (Generation) $ 324 $ 331 $ 872 $ 932 __________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs and ZECs to ComEd. (b) For the three and nine months ended September 30, 2021, respectively, ComEd’s Purchased power from Generation of $94 million and $256 million is recorded as Operating revenues from ComEd of $96 million and $249 million and as Purchased power and fuel from ComEd of $2 million and $(7) million at Generation. For the three and nine months ended September 30, 2020 , respectively, ComEd’s Purchased power from Generation of $71 million and $252 million is recorded as Operating revenues from ComEd of $71 million and $241 million and as Purchased power and fuel from ComEd of less than $1 million and $11 million at Generation. (c) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. (d) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. (e) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. (f) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC-approved market-based SOS commodity programs. (g) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process. PHI PHI’s Operating revenues from affiliates are primarily with BSC for services that PHISCO provides to BSC. Service Company Costs for Corporate Support The Registrants receive a variety of corporate support services from BSC. Pepco, DPL, and ACE also receive corporate support services from PHISCO. See Note 1 — Significant Accounting Policies for additional information regarding BSC and PHISCO. The following table presents the service company costs allocated to the Registrants: Operating and maintenance from affiliates Capitalized costs Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 2021 2020 2021 2020 Exelon BSC $ 149 $ 148 $ 431 $ 390 PHISCO 18 15 54 45 Generation BSC $ 145 $ 133 $ 424 $ 406 43 13 76 37 ComEd BSC 71 65 214 204 47 49 148 133 PECO BSC 41 34 120 107 12 20 57 53 BGE BSC 45 38 133 120 20 30 62 88 PHI BSC 40 36 116 107 27 36 88 79 PHISCO — — — — 18 15 54 45 Pepco BSC 23 20 68 61 11 14 36 29 PHISCO 26 28 84 90 7 7 22 20 DPL BSC 14 13 43 38 10 12 29 26 PHISCO 24 24 73 73 6 4 17 13 ACE BSC 14 11 37 32 7 10 22 22 PHISCO 21 21 64 65 5 4 15 12 Current Receivables from/Payables to affiliates The following tables present current receivables from affiliates and current payables to affiliates: September 30, 2021 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 36 $ 9 $ — $ — $ — $ — $ 86 $ — $ 23 $ 154 ComEd $ 103 (a) — — — — — 49 — 6 158 PECO 24 3 1 — — — 25 — 7 60 BGE 15 — — — — — 32 — 2 49 PHI — — — — — — — 2 — 10 12 Pepco 22 — — — 1 — 15 13 — 51 DPL 4 — — — — — 9 11 — 24 ACE 7 — — — — — 9 9 1 26 Other 9 2 — 1 — — 1 2 — 15 Total $ 184 $ 41 $ 9 $ 2 $ — $ 1 $ 1 $ 229 $ 33 $ 49 $ 549 December 31, 2020 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 13 $ — $ — $ — $ — $ — $ 72 $ — $ 22 $ 107 ComEd $ 78 (a) — — — — — 59 — 9 146 PECO 17 1 — — — — 28 — 4 50 BGE 11 — — — — — 47 — 3 61 PHI — — — — — — — 4 — 11 15 Pepco 13 2 — 1 — — 25 14 — 55 DPL 3 1 — — — — 21 10 1 36 ACE 6 — — — — — 15 9 1 31 Other 25 5 2 2 2 1 6 — — 43 Total $ 153 $ 22 $ 2 $ 3 $ 2 $ 1 $ 6 $ 271 $ 33 $ 51 $ 544 __________ (a) As of September 30, 2021 and December 31, 2020, Generation had a contract liability with ComEd for $27 million and $50 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. As of September 30, 2021 and December 31, 2020, ComEd had a Current Payable to Generation of $76 million and $28 million, respectively, on its Consolidated Balance Sheets, which consisted of Generation’s Current Receivable from ComEd, partially offset by Generation’s contract liability with ComEd. Borrowings from Exelon/PHI intercompany money pool To provide an additional short-term borrowing option that will generally be more favorable to the borrowing participants than the cost of external financing both Exelon and PHI operate an intercompany money pool. Generation, ComEd, PECO, and PHI Corporate participate in the Exelon money pool. Pepco, DPL, and ACE participate in the PHI intercompany money pool. Noncurrent Receivables from/Payables to affiliates Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information. The following table presents noncurrent receivables from affiliates at ComEd and PECO which are recorded as noncurrent payables to affiliates at Generation: September 30, 2021 December 31, 2020 ComEd $ 2,597 $ 2,541 PECO 546 475 Long-term debt to financing trusts The following table presents Long-term debt to financing trusts: September 30, 2021 December 31, 2020 Exelon ComEd PECO Exelon ComEd PECO ComEd Financing III $ 206 $ 205 $ — $ 206 $ 205 $ — PECO Trust III 81 — 81 81 — 81 PECO Trust IV 103 — 103 103 — 103 Total $ 390 $ 205 $ 184 $ 390 $ 205 $ 184 Long-term debt to affiliates In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term debt to affiliates in Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate.

Planned Separation

Planned Separation	9 Months Ended
Planned Separation	Sep. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Planned Separation	Planned SeparationOn February 21, 2021, Exelon’s Board of Directors approved a plan to separate the Utility Registrants and Generation, creating two publicly traded companies. Under the separation plan, Exelon shareholders will retain their current shares of Exelon stock and receive a pro-rata distribution of shares of the new company’s stock in a transaction that is expected to be tax-free to Exelon and its shareholders for U.S. federal income tax purposes. The actual number of shares to be distributed to Exelon shareholders will be determined prior to closing.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2021
Accounting Policies [Abstract]
Description of Business and Basis of Presentation (All Registrants) [Policy Text Block]	Description of Business (All Registrants) Exelon is a utility services holding company engaged in the generation, delivery and marketing of energy through Generation and the energy distribution and transmission businesses through ComEd, PECO, BGE, Pepco, DPL, and ACE. Name of Registrant Business Service Territories Exelon Generation Generation, physical delivery and marketing of power across multiple geographical regions through its customer-facing business, Constellation, which sells electricity to both wholesale and retail customers. Generation also sells natural gas, renewable energy, and other energy-related products and services. Five reportable segments: Mid-Atlantic, Midwest, New York, ERCOT, and Other Power Regions Commonwealth Edison Company Purchase and regulated retail sale of electricity Northern Illinois, including the City of Chicago Transmission and distribution of electricity to retail customers PECO Energy Company Purchase and regulated retail sale of electricity and natural gas Southeastern Pennsylvania, including the City of Philadelphia (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Pennsylvania counties surrounding the City of Philadelphia (natural gas) Baltimore Gas and Electric Company Purchase and regulated retail sale of electricity and natural gas Central Maryland, including the City of Baltimore (electricity and natural gas) Transmission and distribution of electricity and distribution of natural gas to retail customers Pepco Holdings LLC Utility services holding company engaged, through its reportable segments Pepco, DPL, and ACE Service Territories of Pepco, DPL, and ACE Potomac Electric Purchase and regulated retail sale of electricity District of Columbia, and major portions of Montgomery and Prince George’s Counties, Maryland Transmission and distribution of electricity to retail customers Delmarva Power & Purchase and regulated retail sale of electricity and natural gas Portions of Delaware and Maryland (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Portions of New Castle County, Delaware (natural gas) Atlantic City Electric Company Purchase and regulated retail sale of electricity Portions of Southern New Jersey Transmission and distribution of electricity to retail customers Basis of Presentation (All Registrants) This is a combined quarterly report of all Registrants. The Notes to the Consolidated Financial Statements apply to the Registrants as indicated parenthetically next to each corresponding disclosure. When appropriate, the Registrants are named specifically for their related activities and disclosures. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology, and supply management services. PHI also has a business services subsidiary, PHISCO, which provides a variety of support services at cost, including legal, accounting, engineering, customer operations, distribution and transmission planning, asset management, system operations, and power procurement, to PHI operating companies. The costs of BSC and PHISCO are directly charged or allocated to the applicable subsidiaries. The results of Exelon’s corporate operations are presented as “Other” in the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of September 30, 2021 and for the three and nine months ended September 30, 2021 and 2020 are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature,
Revenue [Policy Text Block]	The Registrants recognize revenue from contracts with customers to depict the transfer of goods or services to customers at an amount that the entities expect to be entitled to in exchange for those goods or services. Generation’s primary sources of revenue include competitive sales of power, natural gas, and other energy-related products and services. The Utility Registrants’ primary sources of revenue include regulated electric and gas tariff sales, distribution, and transmission services.

Mergers, Acquisitions, and Di_2

Mergers, Acquisitions, and Dispositions (Tables)	9 Months Ended
Mergers, Acquisitions, and Dispositions (Tables)	Sep. 30, 2021
Mergers, Acquisitions, and Dispositions [Abstract]
Schedule of Changes in Ownership Interest [Table Text Block]	The following tables summarize the effects of the changes in Generation's ownership interest in CENG in Exelon's Shareholders' Equity and Generation's Member's Equity: Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Net income attributable to Exelon's common shareholders $ 1,203 $ 1,315 Pre-tax increase in Exelon's common stock for purchase of EDF's 49.99% equity interest (a) 1,080 1,080 Decrease in Exelon's common stock due to deferred tax liabilities resulting from purchase of EDF's 49.99% equity interest (a) (290) (290) Change from net income attributable to common stock and transfers from noncontrolling interest $ 1,993 $ 2,105 Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Net income (loss) attributable to Generation's membership interest $ 607 $ (247) Pre-tax increase in Generation's membership interest for purchase of EDF's 49.99% equity interest (a) 1,080 1,080 Decrease in Generation's membership interest due to deferred tax liabilities resulting from purchase of EDF's 49.99% equity interest (a) (288) (288) Change from net income (loss) attributable to membership interest and transfers from noncontrolling interest $ 1,399 $ 545 _________

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
Regulatory Matters (Tables)	Sep. 30, 2021
Regulated Operations [Abstract]
Public Utilities Distribution Rate Cases [Table Text Block]	The following tables show the completed and pending distribution base rate case proceedings in 2021. Completed Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Service Requested Revenue Requirement (Decrease) Increase Approved Revenue Requirement (Decrease) Increase Approved ROE Approval Date Rate Effective Date ComEd - Illinois (a) April 16, 2020 Electric $ (11) $ (14) 8.38 % December 9, 2020 January 1, 2021 PECO - Pennsylvania September 30, 2020 Natural Gas 69 29 10.24 % June 22, 2021 July 1, 2021 BGE - Maryland (b) May 15, 2020 (amended September 11, 2020) Electric 203 140 9.50 % December 16, 2020 January 1, 2021 Natural Gas 108 74 9.65 % Pepco - District of Columbia (c) May 30, 2019 (amended June 1, 2020) Electric 136 109 9.275 % June 8, 2021 July 1, 2021 Pepco - Maryland (d) October 26, 2020 (amended March 31, 2021) Electric 104 52 9.55 % June 28, 2021 June 28, 2021 DPL - Delaware March 6, 2020 (amended February 2, 2021) Electric 23 14 9.60 % September 15, 2021 October 6, 2020 ACE - New Jersey (e) December 9, 2020 (amended February 26, 2021) Electric 67 41 9.60 % July 14, 2021 January 1, 2022 __________ (a) ComEd's 2021 approved revenue requirement reflects an increase of $50 million for the initial year revenue requirement for 2021 and a decrease of $64 million related to the annual reconciliation for 2019. The revenue requirement for 2021 and the revenue requirement for 2019 provide for a weighted average debt and equity return on distribution rate base of 6.28%, inclusive of an allowed ROE of 8.38%, reflecting the monthly average yields for 30-year treasury bonds plus 580 basis points. (b) Reflects a three-year cumulative multi-year plan for 2021 through 2023. The MDPSC awarded BGE electric revenue requirement increases of $59 million, $39 million, and $42 million, before offsets, in 2021, 2022, and 2023, respectively, and natural gas revenue requirement increases of $53 million, $11 million, and $10 million, before offsets, in 2021, 2022, and 2023, respectively. BGE proposed to use certain tax benefits to fully offset the increases in 2021 and 2022 and partially offset the increase in 2023. However, the MDPSC only utilized the tax benefits to fully offset the increases in 2021 such that customer rates will remain unchanged from 2020 to 2021. The MDPSC has deferred a decision on whether to use certain tax benefits to offset the customer rate increases in 2022 and 2023 and BGE cannot predict the outcome. (c) Reflects a cumulative multi-year plan with 18-months remaining in 2021 through 2022. The DCPSC awarded Pepco electric incremental revenue requirement increases of $42 million and $67 million, before offsets, for the remainder of 2021 and 2022, respectively. However, the DCPSC utilized the acceleration of refunds for certain tax benefits along with other rate relief to partially offset the customer rate increases by $22 million and $40 million for the remainder of 2021 and 2022, respectively. (d) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024. The MDPSC awarded Pepco electric incremental revenue requirement increases of $21 million, $16 million, and $15 million, before offsets, for the 12-month periods ending March 31, 2022, 2023, and 2024, respectively. Pepco proposed to utilize certain tax benefits to fully offset the increase through 2023 and partially offset customer rate increases in 2024. However, the MDPSC only utilized the acceleration of refunds for certain tax benefits to fully offset the increases such that customer rates remain unchanged through March 31, 2022. The MDPSC has deferred decision on whether to use additional tax benefits to offset customer rate increases for periods after March 31, 2022 and Pepco cannot predict the outcome. (e) Requested and approved increases are before New Jersey sales and use tax. The order allows ACE to retain approximately $11 million of certain tax benefits which resulted in a decrease to income tax expense in Exelon's, PHI's, and ACE's Consolidated Statements of Operations and Comprehensive Income in the third quarter of 2021. Pending Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Service Requested Revenue Requirement Increase Requested ROE Expected Approval Timing ComEd - Illinois (a) April 16, 2021 Electric $ 51 7.36 % Fourth quarter of 2021 PECO - Pennsylvania (b) March 30, 2021 Electric 246 10.95 % Fourth quarter of 2021 DPL - Maryland September 1, 2021 Electric 29 10.10 % First quarter of 2022 __________ (a) ComEd's 2022 requested revenue requirement reflects an increase of $40 million for the initial year revenue requirement for 2022 and an increase of $11 million related to the annual reconciliation for 2020. The revenue requirement for 2022 provides for a weighted average debt and equity return on distribution rate base of 5.72%, inclusive of an allowed ROE of 7.36%, reflecting the average monthly yields for 30-year treasury bonds plus 580 basis points. The reconciliation revenue requirement for 2020 provides for a weighted average debt and equity return on distribution rate base of 5.69%, inclusive of an allowed ROE of 7.29%, reflecting the average monthly yields for 30-year treasury bonds plus 580 basis points less a performance metrics penalty of 7 basis points. (b) The Joint Petition for Settlement was filed on September 15, 2021 and recommended for approval by the administrative law judge on October 6, 2021. PAPUC approval is expected in the fourth quarter of 2021.
Public Utilities Transmission Rate Filings [Table Text Block]	The Utility Registrants' transmission rates are each established based on a FERC-approved formula. ComEd, BGE, Pepco, DPL, and ACE are required to file an annual update to the FERC-approved formula on or before May 15, and PECO is required to file on or before May 31, with the resulting rates effective on June 1 of the same year. The annual update for ComEd is based on prior year actual costs and current year projected capital additions (initial year revenue requirement). The annual update for PECO is based on prior year actual costs and current year projected capital additions, accumulated depreciation, and accumulated deferred income taxes. The annual update for BGE, Pepco, DPL, and ACE is based on prior year actual costs and current year projected capital additions, accumulated depreciation, depreciation and amortization expense, and accumulated deferred income taxes. The update for ComEd also reconciles any differences between the revenue requirement in effect beginning June 1 of the prior year and actual costs incurred for that year (annual reconciliation). The update for PECO, BGE, Pepco, DPL, and ACE also reconciles any differences between the actual costs and actual revenues for the calendar year (annual reconciliation). For 2021, the following total increases/(decreases) were included in the Utility Registrants’ electric transmission formula rate updates: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Increase Total Revenue Requirement Increase (b) Allowed Return on Rate Base (c) Allowed ROE (d) ComEd $ 33 $ 12 $ 45 8.20 % 11.50 % PECO (2) 26 24 7.37 % 10.35 % BGE 38 27 65 7.35 % 10.50 % Pepco (9) 21 12 7.68 % 10.50 % DPL 19 33 52 7.20 % 10.50 % ACE 27 24 51 7.45 % 10.50 % __________ (a) All rates are effective June 1, 2021 - May 31, 2022, subject to review by interested parties pursuant to review protocols of each Utility Registrants' tariff. (b) In 2020, ComEd, BGE, Pepco, DPL, and ACE's transmission revenue requirement included a one-time decrease in accordance with the April 24, 2020 settlement agreement related to excess deferred income taxes which now completed has resulted in an increase to the 2021 transmission revenue requirement. In 2020, PECO's transmission revenue requirement included a one-time decrease in accordance with the December 5, 2019 settlement agreement related to refunds which now completed has resulted in an increase to the 2021 transmission revenue requirement. (c) Represents the weighted average debt and equity return on transmission rate bases. (d) As part of the FERC-approved settlements of ComEd’s 2007 and PECO's 2017 rate cases, the rate of return on common equity is 11.50% and 10.35%, respectively, inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the
Public Utilities Energy Efficiency Revenue [Table Text Block]	Energy Efficiency Formula Rate (Exelon and ComEd). ComEd filed its annual energy efficiency formula rate update with the ICC on June 1, 2021. The filing establishes the revenue requirement used to set the rates that will take effect in January 2022 after the ICC’s review and approval. The requested revenue requirement update is based on a reconciliation of the 2020 actual costs plus projected 2022 expenditures. Initial Revenue Requirement Increase Annual Reconciliation Decrease Total Revenue Requirement Increase Requested Return on Rate Base (a) Requested ROE $ 55 $ (1) $ 54 5.72 % 7.36 % __________
Public Utilities General Disclosures [Table Text Block]	The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to the Utility Registrants' customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2021 $ 44 $ — $ — $ 39 $ 5 $ 3 $ 2 $ — December 31, 2020 51 (1) — 45 7 4 3 — __________ (a) Reflects ComEd's unrecognized equity returns/(losses) earned/(incurred) for ratemaking purposes on its electric distribution formula rate regulatory assets. (b) BGE's authorized amounts capitalized for ratemaking purposes primarily relate to earnings on shareholders' investment on its AMI programs. (c) Pepco's and DPL's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on their respective AMI Programs and Energy Efficiency and Demand Response Programs. The earnings on energy efficiency are on Pepco DC and DPL DE programs only.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
Revenue from Contracts with Customers (Tables)	Sep. 30, 2021
Contracts with Customers [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 2021. This disclosure only includes contracts for which the total consideration is fixed and determinable at contract inception. The average contract term varies by customer type and commodity but ranges from one month to several years. This disclosure excludes Generation's power and gas sales contracts as they contain variable volumes and/or variable pricing. This disclosure also excludes the Utility Registrants' gas and electric tariff sales contracts and transmission revenue contracts as they generally have an original expected duration of one year or less and, therefore, do not contain any future, unsatisfied performance obligations to be included in this disclosure. 2021 2022 2023 2024 2025 and thereafter Total Exelon $ 82 $ 125 $ 50 $ 35 $ 184 $ 476 Generation 168 281 92 41 97 679 PHI 2 8 8 6 87 111 Pepco 2 6 6 5 70 89 DPL — 1 1 — 9 11 ACE — 1 1 1 8 11
Contract Assets [Member]
Contracts with Customers [Line Items]
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]	The following table provides a rollforward of the contract assets reflected in Exelon's and Generation's Consolidated Balance Sheets for the three and nine months ended September 30, 2021 and 2020. The Utility Registrants do not have any contract assets. Exelon Generation Balance as of December 31, 2020 $ 144 $ 144 Amounts reclassified to receivables (16) (16) Revenues recognized 13 13 Amounts previously held-for-sale 12 12 Balance as of March 31, 2021 153 153 Amounts reclassified to receivables (12) (12) Revenues recognized 9 9 Balance as of June 30, 2021 150 150 Amounts reclassified to receivables (15) (15) Revenues recognized 14 14 Balance as of September 30, 2021 $ 149 $ 149 Exelon Generation Balance as of December 31, 2019 $ 174 $ 174 Amounts reclassified to receivables (19) (19) Revenues recognized 17 17 Balance as of March 31, 2020 172 172 Amounts reclassified to receivables (26) (26) Revenues recognized 13 13 Balance as of June 30, 2020 159 159 Amounts reclassified to receivables (18) (18) Revenues recognized 19 19 Balance as of September 30, 2020 $ 160 $ 160
Contract Liabilities [Member]
Contracts with Customers [Line Items]
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]	The following table provides a rollforward of the contract liabilities reflected in Exelon's, Generation's, PHI's, Pepco's, DPL's, and ACE's Consolidated Balance Sheets for the three and nine months ended September 30, 2021 and 2020. As of September 30, 2021 and December 31, 2020, ComEd's, PECO's, and BGE's contract liabilities were immaterial. Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2020 $ 151 $ 84 $ 118 $ 94 $ 12 $ 12 Consideration received or due 20 31 — — — — Revenues recognized (27) (64) (2) (2) — — Amounts previously held-for-sale 3 3 — — — — Balance as of March 31, 2021 147 54 116 92 12 12 Consideration received or due 17 39 — — — — Revenues recognized (32) (68) (3) (1) (1) (1) Balance as of June 30, 2021 132 25 113 91 11 11 Consideration received or due 31 93 — — — — Revenues recognized (26) (65) (2) (2) — — Balance as of September 30, 2021 $ 137 $ 53 $ 111 $ 89 $ 11 $ 11 Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2019 $ 33 $ 71 $ — $ — $ — $ — Consideration received or due 20 55 — — — — Revenues recognized (24) (70) — — — — Balance as of March 31, 2020 29 56 — — — — Consideration received or due 13 34 — — — — Revenues recognized (22) (63) — — — — Balance as of June 30, 2020 20 27 — — — — Consideration received or due 154 94 124 98 13 13 Revenues recognized (25) (65) (2) (2) — — Balance as of September 30, 2020 $ 149 $ 56 $ 122 $ 96 $ 13 $ 13 The following table reflects revenues recognized in the three and nine months ended September 30, 2021 and 2020, which were included in contract liabilities at December 31, 2020 and 2019, respectively: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Exelon $ 4 $ 2 $ 38 $ 25 Generation 2 2 81 63 PHI 2 — 7 — Pepco 2 — 5 — DPL — — 1 — ACE — — 1 —

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
Segment Information (Tables)	Sep. 30, 2021
Segment Tables [Line Items]
Analysis and reconciliation of reportable segment information	An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and nine months ended September 30, 2021 and 2020 is as follows: Three Months Ended September 30, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 4,330 $ — $ — $ — $ — $ — $ (319) $ 4,011 Competitive businesses natural gas revenues 575 — — — — — — 575 Competitive businesses other revenues (499) — — — — — (3) (502) Rate-regulated electric revenues — 1,789 762 677 1,444 — (15) 4,657 Rate-regulated natural gas revenues — — 56 93 23 — (3) 169 Shared service and other revenues — — — — 3 534 (537) — Total operating revenues $ 4,406 $ 1,789 $ 818 $ 770 $ 1,470 $ 534 $ (877) $ 8,910 2020 Competitive businesses electric revenues $ 4,201 $ — $ — $ — $ — $ — $ (326) $ 3,875 Competitive businesses natural gas revenues 323 — — — — — — 323 Competitive businesses other revenues 135 — — — — — (3) 132 Rate-regulated electric revenues — 1,643 759 646 1,339 — (22) 4,365 Rate-regulated natural gas revenues — — 54 85 23 — (3) 159 Shared service and other revenues — — — — 6 484 (491) (1) Total operating revenues $ 4,659 $ 1,643 $ 813 $ 731 $ 1,368 $ 484 $ (845) $ 8,853 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Intersegment revenues (c) : 2021 $ 324 $ 9 $ 2 $ 7 $ 3 $ 531 $ (876) $ — 2020 331 15 3 6 6 485 (845) 1 Depreciation and amortization: 2021 $ 866 $ 304 $ 86 $ 142 $ 210 $ 16 $ — $ 1,624 2020 558 294 85 133 200 19 — 1,289 Operating expenses: 2021 $ 3,465 $ 1,428 $ 677 $ 709 $ 1,155 $ 541 $ (858) $ 7,117 2020 4,727 1,302 658 642 1,102 489 (833) 8,087 Interest expense, net: 2021 $ 77 $ 98 $ 40 $ 36 $ 67 $ 79 $ — $ 397 2020 80 95 39 34 67 89 — 404 Income (loss) before income taxes: 2021 $ 814 $ 276 $ 108 $ 32 $ 264 $ (88) $ — $ 1,406 2020 219 256 122 61 215 (87) — 786 Income Taxes: 2021 $ 177 $ 56 $ (3) $ (4) $ (2) $ (50) $ — $ 174 2020 100 60 (16) 8 (1) 65 — 216 Net income (loss): 2021 $ 633 $ 220 $ 111 $ 36 $ 266 $ (37) $ — $ 1,229 2020 117 196 138 53 216 (151) — 569 Capital Expenditures: 2021 $ 367 $ 561 $ 301 $ 287 $ 410 $ 4 $ — $ 1,930 2020 282 554 312 290 386 9 — 1,833 (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. See Note 19— Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2021 Rate-regulated electric revenues $ 660 $ 337 $ 451 $ — $ (4) $ 1,444 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 92 (89) 3 Total operating revenues $ 660 $ 360 $ 451 $ 92 $ (93) $ 1,470 2020 Rate-regulated electric revenues $ 611 $ 314 $ 420 $ — $ (6) $ 1,339 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 91 (85) 6 Total operating revenues $ 611 $ 337 $ 420 $ 91 $ (91) $ 1,368 Intersegment revenues (c) : 2021 $ 2 $ 2 $ 1 $ 91 $ (93) $ 3 2020 3 3 1 90 (91) 6 Depreciation and amortization: 2021 $ 104 $ 53 $ 46 $ 7 $ — $ 210 2020 96 48 48 8 — 200 Operating expenses: 2021 $ 501 $ 295 $ 359 $ 93 $ (93) $ 1,155 2020 465 296 338 94 (91) 1,102 Interest expense, net: 2021 $ 35 $ 15 $ 14 $ 3 $ — $ 67 2020 35 15 15 2 — 67 Income (loss) before income taxes: 2021 $ 136 $ 53 $ 79 $ (4) $ — $ 264 2020 121 28 68 (2) — 215 Income Taxes: 2021 $ 6 $ 3 $ (11) $ — $ — $ (2) 2020 3 1 (7) 2 — (1) Net income (loss): 2021 $ 130 $ 50 $ 90 $ (4) $ — $ 266 2020 118 27 75 (4) — 216 Capital Expenditures: 2021 $ 202 $ 109 $ 97 $ 2 $ — $ 410 2020 188 94 103 1 — 386 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon.
Analysis and reconciliation of reportable segment revenues for Generation	The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,145 $ 123 $ 1,268 $ 4 $ 1,272 Midwest 1,084 (99) 985 — 985 New York 445 10 455 — 455 ERCOT 191 165 356 2 358 Other Power Regions 948 318 1,266 (6) 1,260 Total Competitive Businesses Electric Revenues 3,813 517 4,330 — 4,330 Competitive Businesses Natural Gas Revenues 266 309 575 — 575 Competitive Businesses Other Revenues (c) 95 (594) (499) — (499) Total Generation Consolidated Operating Revenues $ 4,174 $ 232 $ 4,406 $ — $ 4,406 Three Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,327 $ (20) $ 1,307 $ 6 $ 1,313 Midwest 974 68 1,042 1 1,043 New York 401 5 406 — 406 ERCOT 249 74 323 7 330 Other Power Regions 937 186 1,123 (14) 1,109 Total Competitive Businesses Electric Revenues 3,888 313 4,201 — 4,201 Competitive Businesses Natural Gas Revenues 169 154 323 — 323 Competitive Businesses Other Revenues (c) 85 50 135 — 135 Total Generation Consolidated Operating Revenues $ 4,142 $ 517 $ 4,659 $ — $ 4,659 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $635 million and gains of $37 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 567 $ 3 $ 570 $ 586 $ 5 $ 591 Midwest 655 — 655 748 2 750 New York 343 3 346 281 4 285 ERCOT 181 (2) 179 141 6 147 Other Power Regions 233 (22) 211 253 (28) 225 Total RNF for Reportable Segments 1,979 (18) 1,961 2,009 (11) 1,998 Other (b) 881 18 899 336 11 347 Total Generation RNF $ 2,860 $ — $ 2,860 $ 2,345 $ — $ 2,345 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. includes: • unrealized mark-to-market gains of $754 million and gains of $255 million in 2021 and 2020, respectively; • accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 — Early Plant Retirements of $42 million and $24 million in 2021 and 2020 respectively; and • the elimination of intersegment RNF.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended September 30, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 978 $ 509 $ 383 $ 782 $ 309 $ 198 $ 275 Small commercial & industrial 433 113 73 150 36 53 61 Large commercial & industrial 148 67 128 320 244 27 49 Public authorities & electric railroads 11 7 7 15 8 4 3 Other (a) 245 61 104 172 53 56 63 Total rate-regulated electric revenues (b) $ 1,815 $ 757 $ 695 $ 1,439 $ 650 $ 338 $ 451 Rate-regulated natural gas revenues Residential $ — $ 36 $ 57 $ 10 $ — $ 10 $ — Small commercial & industrial — 13 10 5 — 5 — Large commercial & industrial — — 22 2 — 2 — Transportation — 5 — 3 — 3 — Other (c) — 2 6 3 — 3 — Total rate-regulated natural gas revenues (d) $ — $ 56 $ 95 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,815 $ 813 $ 790 $ 1,462 $ 650 $ 361 $ 451 Other revenues Revenues from alternative revenue programs $ (32) $ 3 $ (24) $ 6 $ 9 $ (2) $ — Other rate-regulated electric revenues (e) 6 2 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (26) $ 5 $ (20) $ 8 $ 10 $ (1) $ — Total rate-regulated revenues for reportable segments $ 1,789 $ 818 $ 770 $ 1,470 $ 660 $ 360 $ 451 Three Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 920 $ 518 $ 389 $ 763 $ 307 $ 193 $ 263 Small commercial & industrial 379 104 65 134 36 45 53 Large commercial & industrial 135 66 113 262 195 21 46 Public authorities & electric railroads 10 7 7 14 8 3 3 Other (a) 234 58 78 141 47 44 50 Total rate-regulated electric revenues (b) $ 1,678 $ 753 $ 652 $ 1,314 $ 593 $ 306 $ 415 Rate-regulated natural gas revenues Residential $ — $ 32 $ 55 $ 11 $ — $ 11 $ — Small commercial & industrial — 16 9 6 — 6 — Large commercial & industrial — — 21 1 — 1 — Transportation — 6 — 3 — 3 — Other (c) — 1 3 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 55 $ 88 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,678 $ 808 $ 740 $ 1,337 $ 593 $ 329 $ 415 Other revenues Revenues from alternative revenue programs $ (38) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Other rate-regulated electric revenues (e) 3 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ (35) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Total rate-regulated revenues for reportable segments $ 1,643 $ 813 $ 731 $ 1,368 $ 611 $ 337 $ 420 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $9 million, $15 million at ComEd • $2 million, $3 million at PECO • $4 million, $3 million at BGE • $3 million, $6 million at PHI • $2 million, $3 million at Pepco • $2 million, $3 million at DPL • $1 million, $1 million at ACE (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • less than $1 million at PECO both 2021 and 2020 • $3 million, $3 million at BGE (e) Includes late payment charge revenues.
Year to Date [Member]
Segment Tables [Line Items]
Analysis and reconciliation of reportable segment information	Nine Months Ended September 30, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 12,264 $ — $ — $ — $ — $ — $ (860) $ 11,404 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Competitive businesses natural gas revenues 2,408 — — — — — — 2,408 Competitive businesses other revenues (555) — — — — — (9) (564) Rate-regulated electric revenues — 4,840 2,033 1,866 3,726 — (33) 12,432 Rate-regulated natural gas revenues — — 366 560 118 — (9) 1,035 Shared service and other revenues — — — — 10 1,549 (1,559) — Total operating revenues $ 14,117 $ 4,840 $ 2,399 $ 2,426 $ 3,854 $ 1,549 $ (2,470) $ 26,715 2020 Competitive businesses electric revenues $ 11,367 $ — $ — $ — $ — $ — $ (920) $ 10,447 Competitive businesses natural gas revenues 1,348 — — — — — (3) 1,345 Competitive businesses other revenues 557 — — — — — (5) 552 Rate-regulated electric revenues — 4,499 1,948 1,763 3,425 — (50) 11,585 Rate-regulated natural gas revenues — — 358 521 116 — (5) 990 Shared service and other revenues — — — — 13 1,440 (1,447) 6 Total operating revenues $ 13,272 $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,440 $ (2,430) $ 24,925 Intersegment revenues (c) : 2021 $ 872 $ 19 $ 6 $ 20 $ 10 $ 1,542 $ (2,469) $ — 2020 932 31 7 16 13 1,435 (2,430) 4 Depreciation and amortization: 2021 $ 2,735 $ 893 $ 259 $ 434 $ 614 $ 52 $ 1 $ 4,988 2020 1,161 841 259 405 585 61 — 3,312 Operating expenses: 2021 $ 14,605 $ 3,833 $ 1,908 $ 2,080 $ 3,167 $ 1,572 $ (2,407) $ 24,758 2020 12,674 3,798 1,900 1,903 3,057 1,452 (2,397) 22,387 Interest expense, net: 2021 $ 225 $ 292 $ 119 $ 103 $ 201 $ 241 $ (1) $ 1,180 2020 277 287 108 99 201 269 — 1,241 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Income (loss) before income taxes: 2021 $ (8) $ 750 $ 392 $ 266 $ 538 $ (264) $ 1 $ 1,675 2020 532 446 310 299 340 (262) — 1,665 Income Taxes: 2021 $ 108 $ 141 $ 9 $ (24) $ 3 $ (8) $ — $ 229 2020 41 142 (7) 26 (77) 16 — 141 Net income (loss): 2021 $ (122) $ 609 $ 383 $ 290 $ 535 $ (255) $ 1 $ 1,441 2020 485 304 317 273 418 (278) — 1,519 Capital Expenditures: 2021 $ 1,086 $ 1,723 $ 878 $ 907 $ 1,299 $ 77 $ — $ 5,970 2020 1,212 1,583 824 838 1,072 77 — 5,606 Total assets: September 30, 2021 $ 48,010 $ 36,002 $ 13,733 $ 12,197 $ 24,502 $ 8,387 $ (10,210) $ 132,621 December 31, 2020 48,094 34,466 12,531 11,650 23,736 9,005 (10,165) 129,317 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. See Note 19 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2021 Rate-regulated electric revenues $ 1,736 $ 922 $ 1,080 $ — $ (12) $ 3,726 Rate-regulated natural gas revenues — 118 — — — 118 Shared service and other revenues — — — 281 (271) 10 Total operating revenues $ 1,736 $ 1,040 $ 1,080 $ 281 $ (283) $ 3,854 2020 Rate-regulated electric revenues $ 1,650 $ 838 $ 952 $ — $ (15) $ 3,425 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 279 (266) 13 Total operating revenues $ 1,650 $ 954 $ 952 $ 279 $ (281) $ 3,554 Intersegment revenues (c) : 2021 $ 4 $ 6 $ 2 $ 281 $ (283) $ 10 2020 6 7 3 278 (281) 13 Depreciation and amortization: 2021 $ 302 $ 157 $ 133 $ 22 $ — $ 614 2020 282 143 134 26 — 585 Operating expenses: 2021 $ 1,396 $ 858 $ 911 $ 285 $ (283) $ 3,167 2020 1,364 843 847 284 (281) 3,057 Interest expense, net: 2021 $ 104 $ 47 $ 43 $ 7 $ — $ 201 2020 103 47 45 6 — 201 Income (loss) before income taxes: 2021 $ 273 $ 144 $ 129 $ (8) $ — $ 538 2020 211 71 67 (9) — 340 Income Taxes: 2021 $ 9 $ 9 $ (12) $ (3) $ — $ 3 2020 (16) (20) (39) (2) — (77) Net income (loss): 2021 $ 264 $ 135 $ 141 $ (5) $ — $ 535 2020 227 91 106 (6) — 418 Capital Expenditures: 2021 $ 641 $ 320 $ 336 $ 2 $ — $ 1,299 2020 512 278 281 1 — 1,072 Total assets: September 30, 2021 $ 9,748 $ 5,295 $ 4,532 $ 4,977 $ (50) $ 24,502 December 31, 2020 9,264 5,140 4,286 5,079 (33) 23,736 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon.
Analysis and reconciliation of reportable segment revenues for Generation	The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Nine Months Ended September 30, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,377 $ 134 $ 3,511 $ 16 $ 3,527 Midwest 3,067 (123) 2,944 1 2,945 New York 1,204 (30) 1,174 (1) 1,173 ERCOT 724 155 879 11 890 Other Power Regions 3,043 713 3,756 (27) 3,729 Total Competitive Businesses Electric Revenues 11,415 849 12,264 — 12,264 Competitive Businesses Natural Gas Revenues 1,384 1,024 2,408 — 2,408 Competitive Businesses Other Revenues (c) 291 (846) (555) — (555) Total Generation Consolidated Operating Revenues $ 13,090 $ 1,027 $ 14,117 $ — $ 14,117 Nine Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,692 $ (152) $ 3,540 $ 21 $ 3,561 Midwest 2,773 240 3,013 (6) 3,007 New York 1,074 (12) 1,062 (1) 1,061 ERCOT 579 155 734 20 754 Other Power Regions 2,718 300 3,018 (34) 2,984 Total Competitive Businesses Electric Revenues 10,836 531 11,367 — 11,367 Competitive Businesses Natural Gas Revenues 881 467 1,348 — 1,348 Competitive Businesses Other Revenues (c) 268 289 557 — 557 Total Generation Consolidated Operating Revenues $ 11,985 $ 1,287 $ 13,272 $ — $ 13,272 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $958 million and gains of $238 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 1,698 $ 14 $ 1,712 $ 1,660 $ 23 $ 1,683 Midwest 2,014 1 2,015 2,180 (2) 2,178 New York 873 7 880 714 11 725 ERCOT (775) (147) (922) 311 14 325 Other Power Regions 641 (77) 564 608 (70) 538 Total RNF for Reportable Segments 4,451 (202) 4,249 5,473 (24) 5,449 Other (b) 1,563 202 1,765 838 24 862 Total Generation RNF $ 6,014 $ — $ 6,014 $ 6,311 $ — $ 6,311 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Primarily includes: • unrealized mark-to-market gains of $1,242 million and gains of $472 million in 2021 and 2020, respectively; • accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 — Early Plant Retirements of $148 million and $24 million in 2021 and 2020 respectively; and • the elimination of intersegment RNF.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,479 $ 1,325 $ 1,044 $ 1,924 $ 785 $ 535 $ 604 Small commercial & industrial 1,176 312 202 392 101 145 146 Large commercial & industrial 420 183 342 825 616 70 139 Public authorities & electric railroads 33 24 20 45 24 11 10 Other (a) 676 167 269 453 154 143 158 Total rate-regulated electric revenues (b) $ 4,784 $ 2,011 $ 1,877 $ 3,639 $ 1,680 $ 904 $ 1,057 Rate-regulated natural gas revenues Residential $ — $ 251 $ 354 $ 67 $ — $ 67 $ — Small commercial & industrial — 94 59 29 — 29 — Large commercial & industrial — — 103 5 — 5 — Transportation — 17 — 11 — 11 — Other (c) — 4 41 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 366 $ 557 $ 118 $ — $ 118 $ — Total rate-regulated revenues from contracts with customers $ 4,784 $ 2,377 $ 2,434 $ 3,757 $ 1,680 $ 1,022 $ 1,057 Other revenues Revenues from alternative revenue programs $ 32 $ 20 $ (17) $ 94 $ 54 $ 17 $ 23 Other rate-regulated electric revenues (e) 24 2 7 3 2 1 — Other rate-regulated natural gas revenues (e) — — 2 — — — — Total other revenues $ 56 $ 22 $ (8) $ 97 $ 56 $ 18 $ 23 Total rate-regulated revenues for reportable segments $ 4,840 $ 2,399 $ 2,426 $ 3,854 $ 1,736 $ 1,040 $ 1,080 Nine Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,389 $ 1,277 $ 1,034 $ 1,825 $ 779 $ 501 $ 545 Small commercial & industrial 1,067 291 183 355 101 127 127 Large commercial & industrial 388 174 311 755 558 66 131 Public authorities & electric railroads 33 21 20 45 25 10 10 Other (a) 663 171 233 471 166 148 159 Total rate-regulated electric revenues (b) $ 4,540 $ 1,934 $ 1,781 $ 3,451 $ 1,629 $ 852 $ 972 Rate-regulated natural gas revenues Residential $ — $ 252 $ 342 $ 68 $ — $ 68 $ — Small commercial & industrial — 86 55 30 — 30 — Large commercial & industrial — — 96 3 — 3 — Transportation — 18 — 10 — 10 — Other (c) — 3 16 5 — 5 — Total rate-regulated natural gas revenues (d) $ — $ 359 $ 509 $ 116 $ — $ 116 $ — Total rate-regulated revenues from contracts with customers $ 4,540 $ 2,293 $ 2,290 $ 3,567 $ 1,629 $ 968 $ 972 Other revenues Revenues from alternative revenue programs $ (51) $ 10 $ (10) $ (15) $ 20 $ (15) $ (20) Other rate-regulated electric revenues (e) 10 3 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (41) $ 13 $ (6) $ (13) $ 21 $ (14) $ (20) Total rate-regulated revenues for reportable segments $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,650 $ 954 $ 952 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $19 million, $31 million at ComEd • $5 million, $6 million at PECO • $10 million, $9 million at BGE • $10 million, $13 million at PHI • $4 million, $6 million at Pepco • $6 million, $7 million at DPL • $2 million, $3 million at ACE (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates in 2021 and 2020 respectively of: • $1 million, $1 million at PECO • $10 million, $7 million at BGE (e) Includes late payment charge revenues.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	9 Months Ended
Accounts Receivable (Tables)	Sep. 30, 2021
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Allowance for credit loss rollforward	The following tables present the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2021 $ 395 $ 75 $ 89 $ 111 $ 27 $ 93 $ 38 $ 19 $ 36 Plus: Current period provision for expected credit losses (a) 47 10 11 1 7 18 5 3 10 Less: Write-offs, net of recoveries (b) 33 1 12 11 3 6 2 4 — Balance as of September 30, 2021 $ 409 $ 84 $ 88 $ 101 $ 31 $ 105 $ 41 $ 18 $ 46 Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 261 $ 33 $ 72 $ 71 $ 23 $ 62 $ 24 $ 18 $ 20 Plus: Current period provision for expected credit losses (c) 114 1 37 27 14 35 11 7 17 Less: Write-offs, net of recoveries (b) 17 1 4 2 2 8 — 3 5 Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2020 $ 366 $ 32 $ 97 $ 116 $ 35 $ 86 $ 32 $ 22 $ 32 Plus: Current period provision for expected credit losses (d) 122 57 23 7 2 33 15 4 14 Less: Write-offs, net of recoveries (b) 79 5 32 22 6 14 6 8 — Balance as of September 30, 2021 $ 409 $ 84 $ 88 $ 101 $ 31 $ 105 $ 41 $ 18 $ 46 Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 243 $ 80 $ 59 $ 55 $ 12 $ 37 $ 13 $ 11 $ 13 Plus: Current period provision for expected credit losses (c) 222 13 62 56 28 63 24 14 25 Less: Write-offs, net of recoveries (b) 51 4 16 15 5 11 2 3 6 Less: Sale of customer accounts receivable (e) 56 56 — — — — — — — Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 __________ (a) For ACE, the increase is primarily a result of increased aging of receivables and a slight decrease in the expected recovery rate. (b) Recoveries were not material to the Registrants. (c) For the Utility Registrants, the increase is primarily as a result of increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnections of service to customers previously disconnected due to COVID-19. (d) For Generation, primarily relates to the impacts of the February 2021 extreme cold weather event. See Note 3 — Regulatory Matters for additional information. For PHI, Pepco, and ACE, the increase is primarily a result of increased aging of receivables and a slight decrease in the expected recovery rate. (e) See below for additional information on the sale of customer accounts receivable at Generation in the second quarter of 2020. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2021 $ 72 $ 1 $ 18 $ 7 $ 8 $ 38 $ 16 $ 9 $ 13 Plus: Current period provision for expected credit losses 9 3 2 1 1 2 1 (1) 2 Less: Write-offs, net of recoveries (a) 4 — 1 1 1 — — — — Balance as of September 30, 2021 $ 77 $ 4 $ 19 $ 7 $ 8 $ 40 $ 17 $ 8 $ 15 Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 61 $ — $ 22 $ 7 $ 6 $ 26 $ 11 $ 7 $ 8 Plus: Current period provision for expected credit losses 15 — 5 1 3 6 2 1 3 Less: Write-offs, net of recoveries (a) 1 — — 1 — — — — — Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2020 $ 71 $ — $ 21 $ 8 $ 9 $ 33 $ 13 $ 9 $ 11 Plus: Current period provision for expected credit losses 15 4 — 2 2 7 4 (1) 4 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 — — — — Balance as of September 30, 2021 $ 77 $ 4 $ 19 $ 7 $ 8 $ 40 $ 17 $ 8 $ 15 Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 48 $ — $ 20 $ 7 $ 5 $ 16 $ 7 $ 4 $ 5 Plus: Current period provision for expected credit losses 36 — 9 3 7 17 6 4 7 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 1 — — 1 Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 __________ (a) Recoveries were not material to the Registrants.
Unbilled customer revenue	The following table provides additional information about unbilled customer revenues recorded in the Registrants' Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 $ 941 $ 359 $ 224 $ 113 $ 98 $ 147 $ 70 $ 34 $ 43 December 31, 2020 998 258 218 147 197 178 87 62 29 __________ (a) Unbilled customer revenues are classified in Customer accounts receivables, net in the Registrants' Consolidated Balance Sheets.
Purchases and sales of accounts receivable	The following table summarizes the impact of the sale of certain receivables: September 30, 2021 December 31, 2020 Derecognized receivables transferred at fair value $ 1,401 $ 1,139 Cash proceeds received 900 500 DPP 501 639 Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Loss on sale of receivables (a) $ 1 $ 8 $ 26 $ 23 __________ (a) Reflected in Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Nine Months Ended September 30, 2021 2020 Proceeds from new transfers (a) $ 4,440 $ 1,889 Cash collections received on DPP and reinvested in the Facility (b) 2,652 2,518 Cash collections reinvested in the Facility 7,092 4,407 __________ (a) Customer accounts receivable sold into the Facility were $7,373 million and $4,515 million for the nine months ended September 30, 2021 and September 30, 2020, respectively. (b) Does not include the $400 million in cash proceeds received from the Purchasers in the first quarter of 2021. Generation is required, under supplier tariffs in ISO-NE, MISO, NYISO, and PJM, to sell customer and other receivables to utility companies, which include the Utility Registrants. The Utility Registrants are required, under separate legislation and regulations in Illinois, Pennsylvania, Maryland, District of Columbia, Delaware, and New Jersey, to purchase certain receivables from alternative retail electric and, as applicable, natural gas suppliers that participate in the utilities' consolidated billing. The following tables present the total receivables purchased and sold. Nine Months Ended September 30, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 2,945 $ — $ 810 $ 795 $ 531 $ 826 $ 504 $ 166 $ 156 Total receivables sold 100 117 — — — — — — — Related party transactions: Receivables purchased from Generation — — — — 17 — — — — Receivables sold to the Utility Registrants — 17 — — — — — — — Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 2,698 $ — $ 865 $ 786 $ 508 $ 787 $ 484 $ 160 $ 143 Total receivables sold 542 790 — — — — — — — Related party transactions: Receivables purchased from Generation — — 34 67 75 72 51 13 8 Receivables sold to the Utility Registrants — 248 — — — — — — —

Early Plant Retirements (Tables

Early Plant Retirements (Tables)	9 Months Ended
Early Plant Retirements (Tables)	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Restructuring and Related Costs [Table Text Block]	The total impact for the three and nine months ended September 30, 2021 and 2020 in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income resulting from the initial decision and subsequent reversal of the decision to early retire Byron and Dresden is summarized in the table below. Income statement expense (pre-tax) Three Months Ended September 30, 2021 Nine Months Ended September 30, 2021 Three and Nine Months Ended September 30, 2020 Depreciation and amortization Accelerated depreciation (a) $ 574 $ 1,805 $ 254 Accelerated nuclear fuel amortization 42 148 14 Operating and maintenance One-time charges (94) (94) 220 Other charges 4 8 34 Contractual offset (b) (60) (451) (129) Total $ 466 $ 1,416 $ 393 _________ (a) Includes the accelerated depreciation of plant assets including any ARC. (b) Reflects contractual offset for ARO accretion and ARC depreciation and excludes any changes in earnings in the NDT funds. Decommissioning-related impacts were not offset for the Byron units starting in the second quarter of 2021 due to the inability to recognize a regulatory asset at ComEd. With Generation’s September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. Based on the regulatory agreement with the ICC, decommissioning-related activities are offset in Exelon's and Generation's Consolidated

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	9 Months Ended
Nuclear Decommissioning (Tables)	Sep. 30, 2021
Schedule Of Nuclear Decommissioning [Line Items]
Schedule of Change in Asset Retirement Obligation [Table Text Block]	The following table provides a rollforward of the nuclear decommissioning ARO reflected in Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2020 to September 30, 2021: Nuclear decommissioning ARO at December 31, 2020 (a) $ 11,922 Accretion expense 375 Net increase due to changes in, and timing of, estimated future cash flows 256 Costs incurred related to decommissioning plants (57) Nuclear decommissioning ARO at September 30, 2021 (a) $ 12,496 _________ (a) Includes $74 million and $80 million as the current portion of the ARO at September 30, 2021 and December 31, 2020, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
Income Taxes (Tables)	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The effective income tax rate from continuing operations varies from the U.S. federal statutory rate principally due to the following: Three Months Ended September 30, 2021 Exelon (a) Generation (a) ComEd (a) PECO (a)(b) BGE (a) (b) PHI (a) Pepco (a) DPL (a) ACE (a)(b) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.0 4.4 8.0 (4.1) (13.0) 5.0 3.4 6.4 7.0 Qualified NDT fund income 0.5 0.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.4) (0.7) (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (1.7) — (0.8) (16.2) (1.4) (1.3) (2.0) (0.6) (0.6) Production tax credits and other credits (1.0) (1.4) (0.5) — (0.9) (0.5) (0.5) (0.4) (0.5) Noncontrolling interests (0.4) (0.6) — — — — — — — Excess deferred tax amortization (6.8) — (7.6) (3.4) (17.3) (24.9) (17.6) (19.9) (41.4) Other (c) (4.8) (1.9) 0.3 (0.1) (0.8) — 0.1 (0.6) 0.8 Effective income tax rate 12.4% 21.7% 20.3% (2.8)% (12.5)% (0.8)% 4.4% 5.7% (13.9)% Three Months Ended September 30, 2020 Exelon (a) Generation (a) ComEd (a) PECO (a)(d) BGE (a)(d) PHI (a)(d) Pepco (a)(d) DPL (a)(d) ACE (a)(d) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 12.3 (10.3) 8.1 (6.2) 5.1 5.5 4.6 6.6 6.9 Qualified NDT fund income 13.2 47.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.4) (4.5) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (4.3) — (0.6) (23.3) (1.2) (1.5) (2.1) (0.4) (1.3) Production tax credits and other credits (3.0) (9.2) (0.4) — (0.8) (0.5) (0.5) (0.5) (0.4) Noncontrolling interests 0.8 2.9 — — — — — — — Excess deferred tax amortization (10.1) — (5.6) (3.8) (10.6) (24.9) (20.0) (23.6) (36.8) Tax Settlements (0.2) (0.7) — — — — — — — Other (0.8) (0.9) 1.1 (0.8) (0.3) 0.1 (0.4) 0.7 0.6 Effective income tax rate 27.5% 45.7% 23.4% (13.1)% 13.1% (0.5)% 2.5% 3.6% (10.3)% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) For PECO, the income tax benefit is primarily due to plant basis differences attributable to tax repair deductions. For BGE, the income tax benefit is primarily due to the Maryland multi-year plan which resulted in the acceleration of certain income tax benefits. For ACE, the income tax benefit is primarily due to a distribution rate case settlement which allows ACE to retain certain tax benefits. (c) For Exelon, "Other" is primarily driven by the reversal of the consolidating income tax adjustment recorded at Exelon Corporate in the first quarter of 2021 that was required pursuant to GAAP interim reporting guidance. (d) At PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to storm tax repair deductions. At BGE, PHI, Pepco, DPL and ACE, the lower effective tax rate is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. Nine Months Ended September 30, 2021 Exelon (a) Generation (b) ComEd (a) PECO (a)(c) BGE (a)(c) PHI (a) Pepco (a) DPL (a) ACE (a)(c) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.0 90.2 7.6 (2.6) (10.8) 4.6 2.5 6.5 7.3 Qualified NDT fund income 9.4 (1,932.6) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.8) 130.6 (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (3.9) — (0.7) (12.6) (1.5) (1.3) (1.9) (0.7) (0.6) Production tax credits and other credits (2.6) 425.1 (0.5) — (0.9) (0.5) (0.5) (0.4) (0.5) Noncontrolling interests (0.7) 145.2 — — — — — — — Excess deferred tax amortization (13.9) — (7.2) (3.3) (16.0) (22.8) (17.4) (19.7) (36.3) Other (d) 2.2 (229.5) (1.3) (0.2) (0.7) (0.3) (0.4) (0.2) — Effective income tax rate 13.7% (1,350.0)% 18.8% 2.3% (9.0)% 0.6% 3.3% 6.3% (9.3)% Nine Months Ended September 30, 2020 Exelon (a) Generation (a) ComEd (a)(e) PECO (a)(e) BGE (a)(e) PHI (a)(e) Pepco (a)(e) DPL (a)(e) ACE (a)(e) U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 9.3 — 12.7 (3.4) 5.5 5.0 4.2 6.5 6.8 Qualified NDT fund income 3.2 10.0 — — — — — — — Deferred Prosecution Agreement payments 2.5 — 9.4 — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2) (3.2) (0.3) — (0.1) (0.2) (0.1) (0.3) (0.5) Plant basis differences (4.0) — (0.9) (15.9) (1.8) (2.2) (2.4) (0.5) (3.7) Production tax credits and other credits (2.6) (7.0) (0.4) — (0.4) (0.3) (0.3) (0.2) (0.4) Noncontrolling interests 1.0 3.1 — — — — — — — Excess deferred tax amortization (15.8) — (11.8) (3.5) (15.0) (45.3) (29.2) (53.6) (81.4) Tax Settlements (f) (5.0) (15.7) — — — — — — — Other 0.1 (0.5) 2.1 (0.5) (0.5) (0.6) (0.8) (1.1) — Effective income tax rate 8.5% 7.7% 31.8% (2.3)% 8.7% (22.6)% (7.6)% (28.2)% (58.2)% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) Generation recognized a loss before income taxes for the nine months ended September 30, 2021. As a result, a negative percentage represents an income tax expense for the period presented. (c) For PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to tax repair deductions. For BGE, the income tax benefit is primarily due to the Maryland multi-year plan which resulted in the acceleration of certain income tax benefits. For ACE, the income tax benefit is primarily due to a distribution rate case settlement which allows ACE to retain certain tax benefits. (d) For Exelon, "Other" is primarily driven by the consolidating income tax adjustment recorded at Exelon Corporate in the first quarter of 2021 that was required pursuant to GAAP interim reporting guidance. This incremental expense will reverse by year-end and will not have an impact on annual results. (e) For ComEd, the higher effective tax rate is primarily related to the nondeductible Deferred Prosecution Agreement payments. For PECO, the income tax benefit is primarily related to an increase in plant basis differences attributable to storm tax repairs deductions. For BGE, PHI, Pepco, DPL, and ACE, the income tax benefit is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. (f) Exelon's and Generation’s unrecognized federal and state tax benefits decreased in the first quarter of 2020 by approximately $411 million due to the settlement of a federal refund claim with IRS Appeals. The recognition of these tax benefits resulted in an increase to Exelon's and Generation’s net income of $76 million and $73 million, respectively, in the first quarter of 2020, reflecting a decrease to Exelon's and Generation's income tax expense of $67 million.
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	PHI and ACE have the following unrecognized tax benefits as of September 30, 2021 and December 31, 2020. Exelon's, Generation's, ComEd's, PECO's, BGE's, Pepco's, and DPL's amounts are not material. PHI ACE September 30, 2021 $ 56 $ 16 December 31, 2020 52 15
Allocation of Tax Benefits	The following table presents the allocation of federal tax benefits from Exelon under the Tax Sharing Agreement. Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 $ 64 $ 1 $ 19 $ — $ 17 $ 16 $ — $ — September 30, 2020 64 14 17 — 17 8 6 1

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
Retirement Benefits (Tables)	Sep. 30, 2021
Retirement Benefits [Abstract]
Calculation of Net Periodic Benefit Costs	A portion of the net periodic benefit cost for all plans is capitalized in the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three and nine months ended September 30, 2021 and 2020. Pension Benefits OPEB Three Months Ended September 30, Three Months Ended September 30, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 110 $ 97 $ 20 $ 22 Interest cost 161 190 29 37 Expected return on assets (335) (317) (40) (41) Amortization of: Prior service cost (credit) 1 1 (8) (30) Actuarial loss 150 128 9 12 Settlement charges 12 8 — — Net periodic benefit cost $ 99 $ 107 $ 10 $ — Pension Benefits OPEB Nine Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 330 $ 290 $ 60 $ 67 Interest cost 481 569 86 114 Expected return on assets (1,003) (953) (119) (122) Amortization of: Prior service cost (credit) 3 3 (25) (92) Actuarial loss 449 384 27 36 Curtailment benefits — — (1) — Settlement charges 16 14 — — Net periodic benefit cost $ 276 $ 307 $ 28 $ 3
Allocated Portion of Pension and Postretirement Benefit Costs	The amounts below represent the Registrants' allocated pension and OPEB costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant, and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant, and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2021 2020 2021 2020 Exelon $ 109 $ 107 $ 304 $ 310 Generation 36 30 92 89 ComEd 32 29 97 85 PECO 2 1 5 4 BGE 16 16 47 47 PHI 12 17 36 52 Pepco 2 4 5 11 DPL 1 2 2 6 ACE 3 3 8 10
Defined Contribution Savings Plans	The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans for the three and nine months ended September 30, 2021 and 2020, respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plans Matching Contributions 2021 2020 2021 2020 Exelon $ 38 $ 37 $ 107 $ 104 Generation 14 14 40 41 ComEd 9 9 27 25 PECO 2 3 8 8 BGE 4 4 8 8 PHI 5 3 12 9 Pepco 1 1 3 3 DPL 1 1 3 2 ACE 1 — 2 1

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
Derivative Financial Instruments (Tables)	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	The following tables provide a summary of the derivative fair value balances recorded by Exelon, Generation, and ComEd as of September 30, 2021 and December 31, 2020: Exelon Generation ComEd September 30, 2021 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 1,505 $ 19,631 $ 63 $ (790) $ (17,399) $ 1,505 $ — Mark-to-market derivative assets 661 3,612 5 (201) (2,755) 661 — Total mark-to-market derivative assets 2,166 23,243 68 (991) (20,154) 2,166 — Mark-to-market derivative liabilities (1,710) (18,490) (55) (559) 17,399 (1,705) (5) Mark-to-market derivative liabilities (720) (3,168) (3) (95) 2,755 (511) (209) Total mark-to-market derivative liabilities (2,430) (21,658) (58) (654) 20,154 (2,216) (214) Total mark-to-market derivative net (liabilities) assets $ (264) $ 1,585 $ 10 $ (1,645) $ — $ (50) $ (214) Exelon Generation ComEd December 31, 2020 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 639 $ 2,757 $ 40 $ 103 $ (2,261) $ 639 $ — Mark-to-market derivative assets 554 1,501 4 64 (1,015) 554 — Total mark-to-market derivative assets 1,193 4,258 44 167 (3,276) 1,193 — Mark-to-market derivative liabilities (293) (2,629) (23) 131 2,261 (260) (33) Mark-to-market derivative liabilities (472) (1,335) (2) 118 1,015 (204) (268) Total mark-to-market derivative liabilities (765) (3,964) (25) 249 3,276 (464) (301) Total mark-to-market derivative net assets (liabilities) $ 428 $ 294 $ 19 $ 416 $ — $ 729 $ (301) _________ (a) Exelon and Generation net all available amounts allowed under the derivative authoritative guidance in the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit, and other forms of non-cash collateral. As of September 30, 2021, $1 million of cash collateral posted with external counterparties and an additional $71 million of cash collateral posted with affiliates, including $50 million with ComEd, and as of December 31, 2020, $15 million of cash collateral held with external counterparties, was not offset against derivative positions because such collateral was not associated with any energy-related derivatives, was associated with accrual positions, or had no positions to offset as of the balance sheet date. (b) Includes $2,084 million held and $209 million posted of variation margin with the exchanges as of September 30, 2021 and December 31, 2020 respectively.
Economic Hedges (Commodity Price Risk)	For the three and nine months ended September 30, 2021 and 2020, Exelon and Generation recognized the following net pre-tax commodity mark-to-market gains (losses) which are also located in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. Three Months Ended Nine Months Ended 2021 2020 2021 2020 Income Statement Location (Loss) Gain (Loss) Gain Operating revenues $ (637) $ 39 $ (961) $ 238 Purchased power and fuel 1,392 209 2,209 224 Total Exelon and Generation $ 755 $ 248 $ 1,248 $ 462
Disclosure of Credit Derivatives [Table Text Block]	The following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS, and payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of September 30, 2021. The tables further delineate that exposure by credit rating of the counterparties and provide guidance on the concentration of credit risk to individual counterparties. The amounts in the tables below exclude credit risk exposure from individual retail counterparties, nuclear fuel procurement contracts, and exposure through RTOs, ISOs, NYMEX, ICE, NASDAQ, NGX, and Nodal commodity exchanges. Rating as of September 30, 2021 Total Exposure Before Credit Collateral Credit Collateral (a) Net Exposure Number of Counterparties Greater than 10% of Net Exposure Net Exposure of Counterparties Greater than 10% of Net Exposure Investment grade $ 701 $ 254 $ 447 — $ — Non-investment grade 23 2 21 — — No external ratings Internally rated — investment grade 110 1 109 — — Internally rated — non-investment grade 309 48 261 — — Total $ 1,143 $ 305 $ 838 — $ — Net Credit Exposure by Type of Counterparty As of September 30, 2021 Financial institutions $ 53 Investor-owned utilities, marketers, power producers 652 Energy cooperatives and municipalities 62 Other 71 Total $ 838 _________ (a) As of September 30, 2021, credit collateral held from counterparties where Generation had credit exposure included $188 million of cash and $117 million of letters of credit. The credit collateral does not include non-liquid collateral.
Fair Value of Derivatives with Credit- Risk Related Contingent Features [Table Text Block]	The aggregate fair value of all derivative instruments with credit-risk related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Features September 30, 2021 December 31, 2020 Gross fair value of derivative contracts containing this feature (a) $ (5,289) $ (834) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 2,735 537 Net fair value of derivative contracts containing this feature (c) $ (2,554) $ (297) _________ (a) Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk related contingent features ignoring the effects of master netting agreements. (b) Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which Generation could potentially be required to post collateral. (c) Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.
Cash Collateral and Letters of Credit on Derivative Contracts [Table Text Block]	As of September 30, 2021 and December 31, 2020, Exelon and Generation posted or held the following amounts of cash collateral and letters of credit on derivative contracts with external counterparties, after giving consideration to offsetting derivative and non-derivative positions under master netting agreements. September 30, 2021 December 31, 2020 Cash collateral posted $ 299 $ 511 Letters of credit posted 477 226 Cash collateral held 1,872 110 Letters of credit held 130 40 Additional collateral required in the event of a credit downgrade below investment grade 3,001 1,432

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	9 Months Ended
Debt and Credit Agreements (Tables)	Sep. 30, 2021
Line of Credit Facility [Line Items]
Schedule of Commercial Paper Borrowings [Table Text Block]	The following table reflects the Registrants' commercial paper programs as of September 30, 2021 and December 31, 2020. PECO and BGE had no commercial paper borrowings as of September 30, 2021 and December 31, 2020. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2021 December 31, 2020 September 30, 2021 December 31, 2020 Exelon (a) $ 287 $ 1,031 0.19 % 0.25 % Generation — 340 — % 0.27 % ComEd — 323 — % 0.23 % PHI (b) 287 368 0.19 % 0.24 % Pepco 40 35 0.15 % 0.22 % DPL 22 146 0.15 % 0.24 % ACE 225 187 0.20 % 0.25 % __________ (a) Exelon Corporate had no outstanding commercial paper borrowings as of September 30, 2021 and December 31, 2020. (b) Represents the consolidated amounts of Pepco, DPL, and ACE.
Schedule of Long-term Debt Instruments [Table Text Block]	During the nine months ended September 30, 2021, the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Long-Term Software License Agreements 3.62 % December 1, 2025 $ 4 Procurement of software licenses. Generation West Medway II LIBOR + 3% (a) March 31, 2026 150 Funding for general corporate purposes. Generation Energy Efficiency Project Financing (b) 2.53 % November 30, 2021 1 Funding to install energy conservation measures for the Fort AP Hill project. Generation Energy Efficiency Project Financing (b) 4.24 % November 30, 2021 1 Funding to install energy conservation measures for the Marine Corps. Logistics Project. ComEd First Mortgage Bonds, Series 130 3.13 % March 15, 2051 700 Repay a portion of outstanding commercial paper obligations and two outstanding term loans, and to fund other general corporate purposes. ComEd First Mortgage Bonds, Series 131 2.75 % September 1, 2051 450 Refinance existing indebtedness and for general corporate purposes. PECO First and Refunding Mortgage Bonds 3.05 % March 15, 2051 375 Funding for general corporate purposes. PECO First and Refunding Mortgage Bonds 2.85 % September 15, 2051 375 Refinance existing indebtedness and for general corporate purposes. BGE Senior Notes 2.25 % June 15, 2031 600 Repay a portion of outstanding commercial paper obligations, repay existing indebtedness, and to fund other general corporate purposes. Pepco First Mortgage Bonds 2.32 % March 30, 2031 150 Repay existing indebtedness and for general corporate purposes. Pepco First Mortgage Bonds 3.29 % September 28, 2051 125 Repay existing indebtedness and for general corporate purposes. DPL First Mortgage Bonds 3.24 % March 30, 2051 125 Repay existing indebtedness and for general corporate purposes. ACE First Mortgage Bonds 2.30 % March 15, 2031 350 Refinance existing indebtedness, repay outstanding commercial paper obligations, and for general corporate purposes. __________ (a) The nonrecourse debt has an average blended interest rate. (b) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
Fair Value of Financial Assets and Liabilities (Tables)	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Liabilities Recorded at Amortized Cost	Fair Value of Financial Liabilities Recorded at Amortized Cost The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2021 and December 31, 2020. The Registrants have no financial liabilities classified as Level 1. The carrying amounts of the Registrants’ short-term liabilities as presented in their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. September 30, 2021 December 31, 2020 Carrying Amount Fair Value Carrying Amount Fair Value Level 2 Level 3 Total Level 2 Level 3 Total Long-Term Debt, including amounts due within one year (a) Exelon $ 38,644 $ 40,570 $ 3,289 $ 43,859 $ 36,912 $ 40,688 $ 3,064 $ 43,752 Generation 6,130 5,835 1,111 6,946 6,087 5,648 1,208 6,856 ComEd 9,772 11,344 — 11,344 8,983 11,117 — 11,117 PECO 4,196 4,738 50 4,788 3,753 4,553 50 4,603 BGE 3,960 4,416 — 4,416 3,664 4,366 — 4,366 PHI 7,482 6,030 2,128 8,158 7,006 6,099 1,806 7,905 Pepco 3,441 3,226 990 4,216 3,165 3,336 748 4,084 DPL 1,808 1,433 559 1,992 1,677 1,484 455 1,939 ACE 1,510 1,107 579 1,686 1,413 1,018 602 1,620 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 479 $ 479 $ 390 $ — $ 467 $ 467 ComEd 205 — 255 255 205 — 246 246 PECO 184 — 224 224 184 — 221 221 SNF Obligation Exelon $ 1,209 $ 1,021 $ — $ 1,021 $ 1,208 $ 909 $ — $ 909 Generation 1,209 1,021 — 1,021 1,208 909 — 909 __________ (a) Includes unamortized debt issuance costs which are not fair valued.
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	Recurring Fair Value Measurements The following tables present assets and liabilities measured and recorded at fair value in the Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2021 and December 31, 2020: Exelon and Generation Exelon Generation As of September 30, 2021 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 2,573 $ — $ — $ — $ 2,573 $ 1,673 $ — $ — $ — $ 1,673 NDT fund investments Cash equivalents (b) 647 135 — — 782 647 135 — — 782 Equities 4,373 1,717 1 1,559 7,650 4,373 1,717 1 1,559 7,650 Fixed income Corporate debt (c) — 1,155 287 — 1,442 — 1,155 287 — 1,442 U.S. Treasury and agencies 2,192 29 — — 2,221 2,192 29 — — 2,221 Foreign governments — 54 — — 54 — 54 — — 54 State and municipal debt — 29 — — 29 — 29 — — 29 Other 31 29 — 1,259 1,319 31 29 — 1,259 1,319 Fixed income subtotal 2,223 1,296 287 1,259 5,065 2,223 1,296 287 1,259 5,065 Private credit — — 187 592 779 — — 187 592 779 Private equity — — — 654 654 — — — 654 654 Real estate — — — 802 802 — — — 802 802 NDT fund investments subtotal (d)(e) 7,243 3,148 475 4,866 15,732 7,243 3,148 475 4,866 15,732 Rabbi trust investments Cash equivalents 65 — — — 65 4 — — — 4 Mutual funds 104 — — — 104 35 — — — 35 Fixed income — 10 — — 10 — — — — — Life insurance contracts — 99 34 — 133 — 33 — — 33 Rabbi trust investments subtotal 169 109 34 — 312 39 33 — — 72 Investments in equities (f) 137 — — — 137 137 — — — 137 Commodity derivative assets Economic hedges 5,527 10,633 7,083 — 23,243 5,527 10,633 7,083 — 23,243 Proprietary trading — 56 12 — 68 — 56 12 — 68 Effect of netting and allocation of collateral (g)(h) (4,468) (9,869) (6,808) — (21,145) (4,468) (9,869) (6,808) — (21,145) Commodity derivative assets subtotal 1,059 820 287 — 2,166 1,059 820 287 — 2,166 DPP consideration — 501 — — 501 — 501 — — 501 Exelon Generation As of September 30, 2021 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Total assets 11,181 4,578 796 4,866 21,421 10,151 4,502 762 4,866 20,281 Liabilities Commodity derivative liabilities Economic hedges (4,126) (9,192) (8,554) — (21,872) (4,126) (9,192) (8,340) — (21,658) Proprietary trading — (32) (26) — (58) — (32) (26) — (58) Effect of netting and allocation of collateral (g)(h) 4,123 9,159 6,218 — 19,500 4,123 9,159 6,218 — 19,500 Commodity derivative liabilities subtotal (3) (65) (2,362) — (2,430) (3) (65) (2,148) — (2,216) Deferred compensation obligation — (149) — — (149) — (44) — — (44) Total liabilities (3) (214) (2,362) — (2,579) (3) (109) (2,148) — (2,260) Total net assets (liabilities) $ 11,178 $ 4,364 $ (1,566) $ 4,866 $ 18,842 $ 10,148 $ 4,393 $ (1,386) $ 4,866 $ 18,021 Exelon Generation As of December 31, 2020 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 686 $ — $ — $ — $ 686 $ 124 $ — $ — $ — $ 124 NDT fund investments Cash equivalents (b) 210 95 — — 305 210 95 — — 305 Equities 3,886 2,077 — 1,562 7,525 3,886 2,077 — 1,562 7,525 Fixed income Corporate debt (c) — 1,485 285 — 1,770 — 1,485 285 — 1,770 U.S. Treasury and agencies 1,871 126 — — 1,997 1,871 126 — — 1,997 Foreign governments — 56 — — 56 — 56 — — 56 State and municipal debt — 101 — — 101 — 101 — — 101 Other — 41 — 961 1,002 — 41 — 961 1,002 Fixed income subtotal 1,871 1,809 285 961 4,926 1,871 1,809 285 961 4,926 Private credit — — 212 629 841 — — 212 629 841 Private equity — — — 504 504 — — — 504 504 Real estate — — — 679 679 — — — 679 679 NDT fund investments subtotal (d)(e) 5,967 3,981 497 4,335 14,780 5,967 3,981 497 4,335 14,780 Rabbi trust investments Cash equivalents 60 — — — 60 4 — — — 4 Mutual funds 91 — — — 91 29 — — — 29 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 87 34 — 121 — 28 — — 28 Rabbi trust investments subtotal 151 98 34 — 283 33 28 — — 61 Investments in equities (f) 195 — — — 195 195 — — — 195 Commodity derivative assets Economic hedges 745 1,914 1,599 — 4,258 745 1,914 1,599 — 4,258 Proprietary trading — 17 27 — 44 — 17 27 — 44 Exelon Generation As of December 31, 2020 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Effect of netting and allocation of collateral (g)(h) (607) (1,597) (905) — (3,109) (607) (1,597) (905) — (3,109) Commodity derivative assets subtotal 138 334 721 — 1,193 138 334 721 — 1,193 DPP consideration — 639 — — 639 — 639 — — 639 Total assets 7,137 5,052 1,252 4,335 17,776 6,457 4,982 1,218 4,335 16,992 Liabilities Commodity derivative liabilities Economic hedges (682) (1,928) (1,655) — (4,265) (682) (1,928) (1,354) — (3,964) Proprietary trading — (21) (4) — (25) — (21) (4) — (25) Effect of netting and allocation of collateral (g)(h) 540 1,918 1,067 — 3,525 540 1,918 1,067 — 3,525 Commodity derivative liabilities subtotal (142) (31) (592) — (765) (142) (31) (291) — (464) Deferred compensation obligation — (145) — — (145) — (42) — — (42) Total liabilities (142) (176) (592) — (910) (142) (73) (291) — (506) Total net assets $ 6,995 $ 4,876 $ 660 $ 4,335 $ 16,866 $ 6,315 $ 4,909 $ 927 $ 4,335 $ 16,486 __________ (a) Exelon excludes cash of $689 million and $409 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $222 million and $59 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $54 million and $53 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $292 million and $171 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $54 million and $20 million at September 30, 2021 and December 31, 2020, respectively. (b) Includes $109 million and $116 million of cash received from outstanding repurchase agreements at September 30, 2021 and December 31, 2020, respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (e) below. (c) Includes investments in equities sold short of $(50) million and $(62) million as of September 30, 2021 and December 31, 2020, respectively, held in an investment vehicle primarily to hedge the equity option component of its convertible debt. (d) Includes net derivative liabilities of less than $1 million and net derivative assets of $2 million, which have total notional amounts of $728 million and $1,043 million at September 30, 2021 and December 31, 2020, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the periods ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (e) Excludes net liabilities of $130 million and $181 million at September 30, 2021 and December 31, 2020, respectively, which include certain derivative assets that have notional amounts of $194 million and $104 million at September 30, 2021 and December 31, 2020, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (f) Includes equity investments held by Generation which were previously designated as equity investments without readily determinable fair value but are now publicly traded and therefore have readily determinable fair values. The first investment became publicly traded in the fourth quarter of 2020. Generation records the fair value of these investments in Other current assets in Exelon's and Generation's Consolidated Balance Sheets based on the quoted market prices of the stocks as of the respective balance sheet date. There were no equity investments without readily determinable fair value that became publicly traded during the third quarter of 2021. For investments that became publicly traded during the first half of 2021, unrealized gains o f $220 million were recorded in Other, net in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. (g) Collateral (received) from counterparties, net of collateral paid to counterparties, totaled $(345) million, $(710) million, and $(590) million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of September 30, 2021. Collateral (received)/posted from counterparties, net of collateral paid to counterparties, totaled $(67) million, $321 million, and $162 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of December 31, 2020. (h) Includes $2,084 million held and $209 million posted of variation margin with the exchanges as of September 30, 2021 and December 31, 2020, respectively. As of September 30, 2021, Exelon and Generation have outstanding commitments to invest in private credit, private equity, and real estate investments of approximately $359 million, $174 million, and $371 million, respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation held investments without readily determinable fair values with carrying amounts of $44 million and $32 million as of September 30, 2021, respectively. Exelon and Generation held investments without readily determinable fair values with carrying amounts of $73 million and $55 million as of December 31, 2020, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three and nine months ended September 30, 2021 and for the year ended December 31, 2020. ComEd, PECO, and BGE ComEd PECO BGE As of September 30, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 309 $ — $ — $ 309 $ 247 $ — $ — $ 247 $ 169 $ — $ — $ 169 Rabbi trust investments Mutual funds — — — — 10 — — 10 14 — — 14 Life insurance contracts — — — — — 15 — 15 — — — — Rabbi trust investments subtotal — — — — 10 15 — 25 14 — — 14 Total assets 309 — — 309 257 15 — 272 183 — — 183 Liabilities Deferred compensation obligation — (9) — (9) — (8) — (8) — (6) — (6) Mark-to-market derivative liabilities (b) — — (214) (214) — — — — — — — — Total liabilities — (9) (214) (223) — (8) — (8) — (6) — (6) Total net assets (liabilities) $ 309 $ (9) $ (214) $ 86 $ 257 $ 7 $ — $ 264 $ 183 $ (6) $ — $ 177 ComEd PECO BGE As of December 31, 2020 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 285 $ — $ — $ 285 $ 8 $ — $ — $ 8 $ 120 $ — $ — $ 120 Rabbi trust investments Mutual funds — — — — 9 — — 9 10 — — 10 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 10 — — 10 Total assets 285 — — 285 17 13 — 30 130 — — 130 Liabilities Deferred compensation obligation — (8) — (8) — (9) — (9) — (5) — (5) Mark-to-market derivative liabilities (b) — — (301) (301) — — — — — — — — Total liabilities — (8) (301) (309) — (9) — (9) — (5) — (5) Total net assets (liabilities) $ 285 $ (8) $ (301) $ (24) $ 17 $ 4 $ — $ 21 $ 130 $ (5) $ — $ 125 __________ (a) ComEd excludes cash of $145 million and $83 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $107 million and $37 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $44 million and $43 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $105 million and $18 million at September 30, 2021 and December 31, 2020, respectively. BGE excludes cash of $56 million and $24 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $27 million and $1 million at September 30, 2021 and December 31, 2020, respectively. (b) The Level 3 balance consists of the current and noncurrent liability of $5 million and $209 million, respectively, at September 30, 2021 and $33 million and $268 million, respectively, at December 31, 2020 related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL, and ACE As of September 30, 2021 As of December 31, 2020 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 100 $ — $ — $ 100 $ 86 $ — $ — $ 86 Rabbi trust investments Cash equivalents 59 — — 59 55 — — 55 Mutual funds 14 — — 14 14 — — 14 Fixed income — 10 — 10 — 11 — 11 Life insurance contracts — 27 34 61 — 26 34 60 Rabbi trust investments subtotal 73 37 34 144 69 37 34 140 Total assets 173 37 34 244 155 37 34 226 Liabilities Deferred compensation obligation — (19) — (19) — (17) — (17) Total liabilities — (19) — (19) — (17) — (17) Total net assets $ 173 $ 18 $ 34 $ 225 $ 155 $ 20 $ 34 $ 209 Pepco DPL ACE As of September 30, 2021 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 36 $ — $ — $ 36 $ 26 $ — $ — $ 26 $ 14 $ — $ — $ 14 Rabbi trust investments Cash equivalents 58 — — 58 — — — — — — — — Fixed income — — — — — — — — — — — — Life insurance contracts — 27 34 61 — — — — — — — — Rabbi trust investments subtotal 58 27 34 119 — — — — — — — — Total assets 94 27 34 155 26 — — 26 14 — — 14 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 94 $ 25 $ 34 $ 153 $ 26 $ — $ — $ 26 $ 14 $ — $ — $ 14 Pepco DPL ACE As of December 31, 2020 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 35 $ — $ — $ 35 $ — $ — $ — $ — $ 13 $ — $ — $ 13 Rabbi trust investments Cash equivalents 53 — — 53 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 34 60 — — — — — — — — Rabbi trust investments subtotal 53 28 34 115 — — — — — — — — Total assets 88 28 34 150 — — — — 13 — — 13 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 88 $ 26 $ 34 $ 148 $ — $ — $ — $ — $ 13 $ — $ — $ 13 __________ (a) PHI excludes cash of $57 million and $74 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $19 million and $30 million at September 30, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at September 30, 2021 and December 31, 2020, respectively. DPL excludes cash of $13 million and $15 million at September 30, 2021 and December 31, 2020, respectively. ACE excludes cash of $16 million and $17 million at September 30, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at September 30, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets.
Fair Value Reconciliation of Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	Reconciliation of Level 3 Assets and Liabilities The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2021 and 2020: Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2021 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2021 $ (235) $ 461 $ (465) $ (4) $ (265) $ 34 $ — Total realized / unrealized gains (losses) Included in net income (967) 3 (970) (a) (967) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11) Included in regulatory assets 62 — — — 51 (b) — 11 Change in collateral (413) — (413) (413) — — — Purchases, sales, and settlements Purchases 8 2 6 8 — — — Sales 6 — 6 6 — — — Settlements (2) (2) — (2) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 (27) — (27) (c) (27) — — — Balance at September 30, 2021 $ (1,566) $ 475 $ (1,861) $ (1,386) $ (214) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2021 $ (1,001) $ 3 $ (1,004) $ (1,001) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine months ended September 30, 2021 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2020 $ 660 $ 497 $ 430 $ 927 $ (301) $ 34 $ — Total realized / unrealized gains (losses) Included in net income (1,600) 4 (1,606) (a) (1,602) — 2 — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets 105 — — — 87 (b) — 18 Change in collateral (751) — (751) (751) — — — Purchases, sales, and settlements Purchases 123 3 120 123 — — — Sales 7 — 7 7 — — — Settlements (50) (48) — (48) — (2) — Transfers into Level 3 4 1 3 (c) 4 — — — Transfers out of Level 3 (64) — (64) (c) (64) — — — Balance as of September 30, 2021 $ (1,566) $ 475 $ (1,861) $ (1,386) $ (214) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2021 $ (1,521) $ 4 $ (1,527) $ (1,523) $ — $ 2 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2020 $ 883 $ 499 $ 659 $ 1,158 $ (318) $ 43 $ — Total realized / unrealized gains (losses) Included in net income (327) 3 (318) (a) (315) — (12) — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets/liabilities 32 — — — 14 (b) — 18 Change in collateral (79) — (79) (79) — — — Purchases, sales, and settlements Purchases 66 1 65 66 — — — Sales (3) — (3) (3) — — — Settlements — (3) — (3) — 3 — Transfers out of Level 3 9 — 9 (c) 9 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (222) $ 3 $ (213) $ (210) $ — $ (12) $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2019 $ 1,068 $ 511 $ 817 $ 1,328 $ (301) $ 41 $ — Total realized / unrealized gains (losses) Included in net income (483) 1 (474) (a) (473) — (10) — Included in noncurrent payables to affiliates — 17 — 17 — — (17) Included in regulatory assets 14 — — — (3) (b) — 17 Change in collateral (120) — (120) (120) — — — Purchases, sales, and settlements Purchases 136 6 130 136 — — — Sales (27) — (27) (27) — — — Settlements (15) (18) — (18) — 3 — Transfers into Level 3 (5) 1 (6) (c) (5) — — — Transfers out of Level 3 13 — 13 (c) 13 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized (losses) gains related to assets and liabilities as of September 30, 2020 $ (107) $ 1 $ (98) $ (97) $ — $ (10) $ — __________ (a) Includes an addition of $34 million for realized losses and a reduction of $80 million for realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2021. Includes a reduction of $105 million and $376 million for realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2020. (b) Includes $49 million of increases in fair value and an increase for realized losses due to settlements of $2 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2021. Includes $72 million of increases in fair value and an increase for realized losses due to settlements of $15 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2021. Includes $9 million of increases in fair value and an increase for realized losses due to settlements of $5 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2020. Includes $26 million of decrease in fair value and an increase for realized losses due to settlements of $23 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2020. (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts.
Total Realized and Unrealized Gains (Losses) Included in Income for Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2021 and 2020: Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total (losses) gains included in net income for the three months ended September 30, 2021 $ (1,274) $ 304 $ — $ 3 $ (1,274) $ 304 $ 3 $ — Total (losses) gains included in net income for the nine months ended September 30, 2021 (1,944) 338 2 4 (1,944) 338 4 2 Total unrealized (losses) gains for the three months ended September 30, 2021 (1,361) 357 — 3 (1,361) 357 3 — Total unrealized (losses) gains for the nine months ended September 30, 2021 (1,969) 443 2 4 (1,969) 443 4 2 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total losses included in net income for the three months ended September 30, 2020 $ (305) $ (13) $ (12) $ — $ (305) $ (13) $ — $ (12) Total losses included in net income for the nine months ended September 30, 2020 (370) (104) (10) — (370) (104) — (10) Total unrealized (losses) gains for the three months ended September 30, 2020 (216) 3 (12) 3 (216) 3 3 (12) Total unrealized gains (losses) for the nine months ended September 30, 2020 (50) (48) (10) 1 (50) (48) 1 (10)
Fair Value Reconciliation of Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis, Valuation Technique	Mark-to-Market Derivatives (Exelon, Generation, and ComEd) The table below discloses the significant inputs to the forward curve used to value mark-to-market derivatives. Type of trade Fair Value at September 30, 2021 Fair Value at December 31, 2020 Valuation Unobservable 2021 Range & Arithmetic Average 2020 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ (1,257) $ 245 Discounted Forward power $9.77 - $301 $55 $2.25 - $163 $30 Forward gas $1.76 - $23.00 $4.16 $1.57 - $7.88 $2.59 Option Volatility 35% - 197% 49% 11% - 237% 32% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ (14) $ 23 Discounted Forward power $16 - $156 $53 $10 - $106 $27 Mark-to-market derivatives (Exelon and ComEd) $ (214) $ (301) Discounted Forward heat (c) 9x - 10x 9.13x 8x - 9x 8.85x Marketability 3% - 7% 4.77% 3% - 8% 4.93% Renewable 95% - 122% 100% 91% - 123% 99% __________ (a) The valuation techniques, unobservable inputs, ranges and arithmetic averages are the same for the asset and liability positions. (b) The fair values do not include cash collateral (received)/posted on level three positions of $(590) million and $162 million as of September 30, 2021 and December 31, 2020, respectively. (c) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery.

Commitments and Contingencies_2

Commitments and Contingencies (Tables)	9 Months Ended
Commitments and Contingencies (Tables)	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
PHI Merger Commitments	The following amounts represent total commitment costs that have been recorded since the acquisition date and the total remaining obligations for Exelon, PHI, Pepco, DPL, and ACE as of September 30, 2021: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 74 62 51 7 4 __________ (a) Remaining commitments extend through 2026 and include rate credits, energy efficiency programs and delivery system modernization.
Commercial Commitments	The Registrants’ commercial commitments as of September 30, 2021, representing commitments potentially triggered by future events were as follows: Expiration within Total 2021 2022 2023 2024 2025 2026 and beyond Exelon Letters of credit $ 2,241 $ 268 $ 1,860 $ 113 $ — $ — $ — Surety bonds (a) 971 403 566 — 2 — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 31 — 3 3 6 6 13 Total commercial commitments $ 3,621 $ 671 $ 2,429 $ 116 $ 8 $ 6 $ 391 Generation Letters of credit $ 2,223 $ 264 $ 1,846 $ 113 $ — $ — $ — Surety bonds (a) 826 352 474 — — — — Total commercial commitments $ 3,049 $ 616 $ 2,320 $ 113 $ — $ — $ — ComEd Letters of credit $ 7 $ 2 $ 5 $ — $ — $ — $ — Surety bonds (a) 17 5 10 — 2 — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 224 $ 7 $ 15 $ — $ 2 $ — $ 200 PECO Letters of credit $ 1 $ — $ 1 $ — $ — $ — $ — Surety bonds (a) 2 — 2 — — — — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 181 $ — $ 3 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ — $ 2 $ — $ — $ — $ — Surety bonds (a) 3 2 1 — — — — Total commercial commitments $ 5 $ 2 $ 3 $ — $ — $ — $ — PHI Surety bonds (a) $ 23 $ 3 $ 20 $ — $ — $ — $ — Guaranteed lease residual values (b) 31 — 3 3 6 6 13 Total commercial commitments $ 54 $ 3 $ 23 $ 3 $ 6 $ 6 $ 13 Pepco Surety bonds (a) $ 14 $ — $ 14 $ — $ — $ — $ — Guaranteed lease residual values (b) 10 — 1 1 2 2 4 Total commercial commitments $ 24 $ — $ 15 $ 1 $ 2 $ 2 $ 4 DPL Surety bonds (a) $ 5 $ 2 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 13 — 1 1 3 3 5 Total commercial commitments $ 18 $ 2 $ 4 $ 1 $ 3 $ 3 $ 5 ACE Surety bonds (a) $ 4 $ 1 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 8 — 1 1 1 1 4 Total commercial commitments $ 12 $ 1 $ 4 $ 1 $ 1 $ 1 $ 4 __________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $75 million guaranteed by Exelon and PHI, of which $25 million, $32 million, and $18 million is guaranteed by Pepco, DPL, and ACE, respectively. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.
Accrued environmental liabilities	As of September 30, 2021 and December 31, 2020, the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities in their respective Consolidated Balance Sheets: September 30, 2021 December 31, 2020 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 474 $ 310 $ 483 $ 314 Generation 119 — 121 — ComEd 284 284 293 293 PECO 23 21 23 21 BGE 6 5 2 — PHI 42 — 44 — Pepco 40 — 42 — DPL 1 — 1 — ACE 1 — 1 —

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Tables)	9 Months Ended
Changes in Accumulated Other Comprehensive Income (Tables)	Sep. 30, 2021
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income (Loss)	The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended September 30, 2021 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (5) $ (3,264) $ (20) $ (3,289) OCI before reclassifications — 14 (3) 11 Amounts reclassified from AOCI — 55 — 55 Net current-period OCI — 69 (3) 66 Ending balance $ (5) $ (3,195) $ (23) $ (3,223) Three Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (3) $ (3,096) $ (33) $ (3,132) OCI before reclassifications (1) (13) 3 (11) Amounts reclassified from AOCI — 39 — 39 Net current-period OCI (1) 26 3 28 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Nine Months Ended September 30, 2021 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (5) $ (3,372) $ (23) $ (3,400) OCI before reclassifications (1) 15 — 14 Amounts reclassified from AOCI — 163 — 163 Net current-period OCI (1) 178 — 177 Ending balance $ (6) $ (3,194) $ (23) $ (3,223) Nine Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (2) $ (3,165) $ (27) $ (3,194) OCI before reclassifications (2) (17) (3) (22) Amounts reclassified from AOCI — 112 — 112 Net current-period OCI (2) 95 (3) 90 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) ______
Schedule Of Other Comprehensive Income (Loss) Tax	The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 1 $ 4 $ 3 $ 12 Actuarial loss reclassified to periodic benefit cost (19) (16) (57) (50) Pension and non-pension postretirement benefit plans valuation adjustment (7) 3 (8) 6

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
Variable Interest Entities (Tables)	Sep. 30, 2021
Variable Interest Entity [Abstract]
VIE - Assets and Liabilities of VIEs which Creditors or Beneficiaries have no Recourse	Consolidated VIEs The table below shows the carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the consolidated financial statements of Exelon, Generation, PHI, and ACE as of September 30, 2021 and December 31, 2020. The assets, except as noted in the footnotes to the table below, can only be used to settle obligations of the VIEs. The liabilities, except as noted in the footnote to the table below, are such that creditors, or beneficiaries, do not have recourse to the general credit of Exelon, Generation, PHI, and ACE. September 30, 2021 December 31, 2020 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 38 $ 38 $ — $ — $ 98 $ 98 $ — $ — Restricted cash and cash equivalents 47 42 5 5 47 44 3 3 Accounts receivable Customer 25 25 — — 148 148 — — Other 7 7 — — 36 36 — — Unamortized energy contract assets 21 21 — — 22 22 — — Inventories, net Materials and supplies 14 14 — — 244 244 — — Assets held for sale (b) — — — — 101 101 — — Other current assets 517 513 4 — 674 669 5 — Total current assets 669 660 9 5 1,370 1,362 8 3 Property, plant, and equipment, net 2,052 2,052 — — 5,803 5,803 — — Nuclear decommissioning trust funds — — — — 3,007 3,007 — — Unamortized energy contract assets 210 210 — — 249 249 — — Other noncurrent assets 22 13 9 9 52 42 10 10 Total noncurrent assets 2,284 2,275 9 9 9,111 9,101 10 10 Total assets (c) $ 2,953 $ 2,935 $ 18 $ 14 $ 10,481 $ 10,463 $ 18 $ 13 Long-term debt due within one year $ 80 $ 70 $ 10 $ 6 $ 94 $ 68 $ 26 $ 21 Accounts payable 11 11 — — 81 81 — — Accrued expenses 14 14 — — 70 70 — — Unamortized energy contract liabilities — — — — 4 4 — — Liabilities held for sale (b) — — — — 16 16 — — Other current liabilities — — — — 5 5 — — Total current liabilities 105 95 10 6 270 244 26 21 Long-term debt 832 832 — — 889 889 — — Asset retirement obligations 149 149 — — 2,318 2,318 — — Other noncurrent liabilities 3 3 — — 129 129 — — Total noncurrent liabilities 984 984 — — 3,336 3,336 — — Total liabilities (d) $ 1,089 $ 1,079 $ 10 $ 6 $ 3,606 $ 3,580 $ 26 $ 21 _________ (a) Includes certain purchase accounting adjustments from the PHI merger not pushed down to ACE. (b) In the fourth quarter of 2020, Generation entered into an agreement for the sale of a significant portion of Generation's solar business, and as a result of this transaction, Exelon and Generation reclassified the consolidated VIEs' solar assets and liabilities as held for sale. Completion of the transaction occurred in the first quarter of 2021. Refer to Note 2 — Mergers, Acquisitions, and Dispositions for additional information on the solar business. (c) Exelon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $21 million and $22 million, non-current unamortized energy contract assets of $210 million and $249 million, assets held for sale of $0 million and $9 million, and other unrestricted assets of $0 million and $1 million as of September 30, 2021 and December 31, 2020, respectively. (d) Exelon’s and Generation’s balances include liabilities with recourse of $1 million and $8 million as of September 30, 2021 and December 31, 2020, respectively.
VIE - Summary of Unconsolidated VIEs	The following table presents summary information about Exelon's and Generation’s significant unconsolidated VIE entities: September 30, 2021 December 31, 2020 Commercial Equity Total Commercial Equity Total Total assets (a) $ 781 $ 370 $ 1,151 $ 777 $ 401 $ 1,178 Total liabilities (a) 80 209 289 61 223 284 Exelon's ownership interest in VIE (a) — 143 143 — 157 157 Other ownership interests in VIE (a) 701 18 719 716 21 737 _________ (a) These items represent amounts in the unconsolidated VIE balance sheets, not in Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. Exelon and Generation do not have any exposure to loss as they do not have a carrying amount in the equity investment VIEs as of September 30, 2021 and December 31, 2020.

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	9 Months Ended
Supplemental Financial Information (Tables)	Sep. 30, 2021
Supplemental Financial Information [Abstract]
Components of Operating Lease Income	The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Operations and Comprehensive Income. Operating revenues Exelon Generation PHI DPL Three Months Ended September 30, 2021 Operating lease income $ 30 $ 29 $ 1 $ 1 Variable lease income 71 71 — — Three Months Ended September 30, 2020 Operating lease income $ 30 $ 28 $ 1 $ 1 Variable lease income 76 76 — — Nine Months Ended September 30, 2021 Operating lease income $ 47 $ 44 $ 3 $ 3 Variable lease income 208 207 1 1 Nine Months Ended September 30, 2020 Operating lease income $ 48 $ 43 $ 3 $ 3 Variable lease income 225 224 1 1
Taxes Other Than Income Taxes	Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2021 Utility taxes (a) $ 242 $ 27 $ 67 $ 41 $ 21 $ 86 $ 80 $ 6 $ — Property 165 66 13 5 46 34 23 10 1 Payroll 57 26 7 4 5 7 2 1 1 Three Months Ended September 30, 2020 Utility taxes (a) $ 237 $ 26 $ 66 $ 41 $ 21 $ 83 $ 77 $ 5 $ 1 Property 152 66 7 4 42 32 21 10 1 Payroll 59 29 7 4 4 6 2 1 1 Nine Months Ended September 30, 2021 Utility taxes (a) $ 665 $ 73 $ 188 $ 107 $ 66 $ 231 $ 212 $ 17 $ 2 Property 470 199 30 13 131 97 65 30 2 Payroll 180 83 20 12 14 21 5 4 2 Nine Months Ended September 30, 2020 Utility taxes (a) $ 651 $ 75 $ 181 $ 102 $ 65 $ 228 $ 210 $ 16 $ 2 Property 449 199 23 12 121 94 63 29 2 Payroll 183 88 21 12 13 21 6 4 3 __________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Schedule of Other Nonoperating Income, by Component	Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 263 $ 263 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 102 102 — — — — — — — Net unrealized losses on NDT funds Regulatory Agreement Units (195) (195) — — — — — — — Non-Regulatory Agreement Units (88) (88) — — — — — — — Regulatory offset to NDT fund-related activities (b) (38) (38) — — — — — — — Decommissioning-related activities 44 44 — — — — — — — AFUDC — Equity 36 — 10 7 7 12 9 2 1 Non-service net periodic benefit cost 19 — — — — — — — — Net unrealized losses from equity investments (c) (179) (179) — — — — — — — Three Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 50 $ 50 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 23 23 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 398 398 — — — — — — — Non-Regulatory Agreement Units 254 254 — — — — — — — Regulatory offset to NDT fund-related activities (b) (359) (359) — — — — — — — Decommissioning-related activities 366 366 — — — — — — — AFUDC — Equity 27 — 7 5 6 9 7 1 1 Non-service net periodic benefit cost 15 — — — — — — — — Other, net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 698 $ 698 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 392 392 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 84 84 — — — — — — — Non-Regulatory Agreement Units 38 38 — — — — — — — Regulatory offset to NDT fund-related activities (b) (607) (607) — — — — — — — Decommissioning-related activities 605 605 — — — — — — — AFUDC — Equity 99 — 23 19 21 36 30 4 2 Non-service net periodic benefit cost 64 — — — — — — — — Net unrealized losses from equity investments (c) (83) (83) — — — — — — — Nine Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 127 $ 127 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 127 127 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units 111 111 — — — — — — — Non-Regulatory Agreement Units 1 1 — — — — — — — Regulatory offset to NDT fund-related activities (b) (192) (192) — — — — — — — Decommissioning-related activities 174 174 — — — — — — — AFUDC — Equity 76 — 22 12 16 26 20 3 3 Non-service net periodic benefit cost 38 — — — — — — — — __________ (a) Realized income includes interest, dividends and realized gains and losses on sales of NDT fund investments. (b) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units except for decommissioning-related impacts that were not offset for the Byron units starting in the second quarter of 2021, including the elimination of income taxes related to all NDT fund activity for those units. With Generation's September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning and Note 8 — Nuclear Decommissioning for additional information on the contractual offset suspension for the Byron units. (c) Net unrealized losses from equity investments that became publicly traded entities in the fourth quarter of 2020 and the first half of 2021.
Cash Flow Supplemental Disclosures	The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Cash Flows. Depreciation, amortization, and accretion Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Property, plant, and equipment (a) $ 4,505 $ 2,698 $ 721 $ 249 $ 324 $ 467 $ 204 $ 126 $ 115 Amortization of regulatory assets (a) 439 — 172 10 110 147 98 31 18 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 23 23 — — — — — — — Nuclear fuel (c) 810 810 — — — — — — — ARO accretion (d) 383 383 — — — — — — — Total depreciation, amortization, and accretion $ 6,204 $ 3,951 $ 893 $ 259 $ 434 $ 614 $ 302 $ 157 $ 133 Nine Months Ended September 30, 2020 Property, plant, and equipment (a) $ 2,831 $ 1,121 $ 689 $ 238 $ 293 $ 436 $ 191 $ 116 $ 104 Amortization of regulatory assets (a) 434 — 152 21 112 149 91 27 30 Amortization of intangible assets, net (a) 47 40 — — — — — — — Amortization of energy contract assets and liabilities (b) 24 22 — — — — — — — Nuclear fuel (c) 708 708 — — — — — — — ARO accretion (d) 375 375 — — — — — — — Total depreciation, amortization, and accretion $ 4,419 $ 2,266 $ 841 $ 259 $ 405 $ 585 $ 282 $ 143 $ 134 __________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2021 Pension and non-pension postretirement benefit costs $ 304 $ 92 $ 97 $ 5 $ 45 $ 36 $ 5 $ 2 $ 8 Allowance for credit losses 155 59 34 36 7 18 9 3 6 Other decommissioning-related activity (a) (810) (810) — — — — — — — Energy-related options (b) 45 45 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) (129) — (32) (20) 17 (94) (54) (17) (23) Severance costs (67) (75) 1 — — 1 — — — Long-term incentive plan 94 — — — — — — — — Amortization of operating ROU asset 146 98 2 — 22 21 5 7 3 AFUDC — Equity (99) — (23) (19) (21) (36) (30) (4) (2) Nine Months Ended September 30, 2020 Pension and non-pension postretirement benefit costs $ 310 $ 89 $ 85 $ 4 $ 46 $ 52 $ 11 $ 6 $ 10 Allowance for credit losses 130 16 23 38 12 41 24 15 2 Other decommissioning-related activity (a) (301) (301) — — — — — — — Energy-related options (b) 79 79 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) 66 — 51 (10) 10 15 (20) 15 20 Severance costs 96 88 1 — — — — — — Provision for excess and obsolete inventory 119 118 1 1 — (1) — (1) — Long-term incentive plan (8) — — — — — — — — Amortization of operating ROU asset 185 135 1 — 23 21 5 6 2 Deferred Prosecution Agreement payments (d) 200 — 200 — — — — — — AFUDC — Equity (76) — (22) (12) (16) (26) (20) (3) (3) __________ (a) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units except for decommissioning-related impacts that were not offset for the Byron units starting in the second quarter of 2021, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income, and income taxes related to all NDT fund activity for these units. With Generation's September 15, 2021 reversal of the previous decision to retire Byron, Generation resumed contractual offset for Byron as of that date. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning and Note 8 — Nuclear Decommissioning for additional information on the contractual offset suspension for the Byron units. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution, energy efficiency, distributed generation, and transmission formula rates. For BGE, Pepco, DPL, and ACE, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO, reflects the change in regulatory assets and liabilities associated with its transmission formula rates. See Note 3 — Regulatory Matters for additional information. (d) See Note 15 — Commitments and Contingencies for additional information related to the Deferred Prosecution Agreement. The following tables provide a reconciliation of cash, cash equivalents, and restricted cash reported within the Registrants’ Consolidated Balance Sheets that sum to the total of the same amounts in their Consolidated Statements of Cash Flows. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 Cash and cash equivalents $ 2,957 $ 1,957 $ 241 $ 344 $ 225 $ 82 $ 19 $ 13 $ 16 Restricted cash and cash equivalents 473 62 276 8 27 71 41 26 5 Restricted cash included in other long-term assets 54 — 44 — — 9 — — 9 Total cash, restricted cash, and cash equivalents $ 3,484 $ 2,019 $ 561 $ 352 $ 252 $ 162 $ 60 $ 39 $ 30 December 31, 2020 Cash and cash equivalents $ 663 $ 226 $ 83 $ 19 $ 144 $ 111 $ 30 $ 15 $ 17 Restricted cash and cash equivalents 438 89 279 7 1 39 35 — 3 Restricted cash included in other long-term assets 53 — 43 — — 10 — — 10 Cash, restricted cash, and cash equivalents - Held for Sale 12 12 — — — — — — — Total cash, restricted cash, and cash equivalents $ 1,166 $ 327 $ 405 $ 26 $ 145 $ 160 $ 65 $ 15 $ 30 September 30, 2020 Cash and cash equivalents $ 1,858 $ 623 $ 76 $ 242 $ 326 $ 196 $ 125 $ 26 $ 13 Restricted cash and cash equivalents 485 100 305 7 1 38 33 — 4 Restricted cash included in other long-term assets 137 — 127 — — 10 — — 10 Total cash, restricted cash, and cash equivalents $ 2,480 $ 723 $ 508 $ 249 $ 327 $ 244 $ 158 $ 26 $ 27 December 31, 2019 Cash and cash equivalents $ 587 $ 303 $ 90 $ 21 $ 24 $ 131 $ 30 $ 13 $ 12 Restricted cash and cash equivalents 358 146 150 6 1 36 33 — 2 Restricted cash included in other long-term assets 177 — 163 — — 14 — — 14 Total cash, restricted cash, and cash equivalents $ 1,122 $ 449 $ 403 $ 27 $ 25 $ 181 $ 63 $ 13 $ 28 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2020 Form 10-K.
Supplemental Balance Sheet Disclosures	The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2021 Compensation-related accruals (a) $ 894 $ 318 $ 148 $ 66 $ 72 $ 108 $ 34 $ 21 $ 16 Taxes accrued 508 222 80 61 90 98 67 16 7 Interest accrued 415 77 65 36 39 75 37 20 15 December 31, 2020 Compensation-related accruals (a) $ 1,069 $ 426 $ 170 $ 73 $ 84 $ 109 $ 36 $ 18 $ 17 Taxes accrued 527 229 94 16 73 117 90 18 12 Interest accrued 331 44 109 37 46 51 26 7 12 __________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation, and benefits.

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
Related Party Transactions (Tables)	Sep. 30, 2021
Related Party Transactions [Abstract]
Operating Revenues and Purchased Power and Fuel	The following table presents Generation’s Operating revenues from affiliates, which are primarily recorded as Purchased power from affiliates and an immaterial amount recorded as Operating and maintenance expense from affiliates at the Utility Registrants: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Operating revenues from affiliates: ComEd (a)(b) $ 96 $ 71 $ 249 $ 241 PECO (c) 59 68 142 146 BGE (d) 65 84 195 252 PHI 99 105 276 288 Pepco (e) 69 80 199 219 DPL (f) 25 21 63 60 ACE (g) 5 4 14 9 Other 5 3 10 5 Total operating revenues from affiliates (Generation) $ 324 $ 331 $ 872 $ 932 __________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs and ZECs to ComEd. (b) For the three and nine months ended September 30, 2021, respectively, ComEd’s Purchased power from Generation of $94 million and $256 million is recorded as Operating revenues from ComEd of $96 million and $249 million and as Purchased power and fuel from ComEd of $2 million and $(7) million at Generation. For the three and nine months ended September 30, 2020 , respectively, ComEd’s Purchased power from Generation of $71 million and $252 million is recorded as Operating revenues from ComEd of $71 million and $241 million and as Purchased power and fuel from ComEd of less than $1 million and $11 million at Generation. (c) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. (d) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. (e) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. (f) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC-approved market-based SOS commodity programs. (g) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process.
BSC and PHISCO Service Companies	The following table presents the service company costs allocated to the Registrants: Operating and maintenance from affiliates Capitalized costs Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 2021 2020 2021 2020 Exelon BSC $ 149 $ 148 $ 431 $ 390 PHISCO 18 15 54 45 Generation BSC $ 145 $ 133 $ 424 $ 406 43 13 76 37 ComEd BSC 71 65 214 204 47 49 148 133 PECO BSC 41 34 120 107 12 20 57 53 BGE BSC 45 38 133 120 20 30 62 88 PHI BSC 40 36 116 107 27 36 88 79 PHISCO — — — — 18 15 54 45 Pepco BSC 23 20 68 61 11 14 36 29 PHISCO 26 28 84 90 7 7 22 20 DPL BSC 14 13 43 38 10 12 29 26 PHISCO 24 24 73 73 6 4 17 13 ACE BSC 14 11 37 32 7 10 22 22 PHISCO 21 21 64 65 5 4 15 12
Current Receivables From/Payables To Affiliates	The following tables present current receivables from affiliates and current payables to affiliates: September 30, 2021 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 36 $ 9 $ — $ — $ — $ — $ 86 $ — $ 23 $ 154 ComEd $ 103 (a) — — — — — 49 — 6 158 PECO 24 3 1 — — — 25 — 7 60 BGE 15 — — — — — 32 — 2 49 PHI — — — — — — — 2 — 10 12 Pepco 22 — — — 1 — 15 13 — 51 DPL 4 — — — — — 9 11 — 24 ACE 7 — — — — — 9 9 1 26 Other 9 2 — 1 — — 1 2 — 15 Total $ 184 $ 41 $ 9 $ 2 $ — $ 1 $ 1 $ 229 $ 33 $ 49 $ 549 December 31, 2020 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 13 $ — $ — $ — $ — $ — $ 72 $ — $ 22 $ 107 ComEd $ 78 (a) — — — — — 59 — 9 146 PECO 17 1 — — — — 28 — 4 50 BGE 11 — — — — — 47 — 3 61 PHI — — — — — — — 4 — 11 15 Pepco 13 2 — 1 — — 25 14 — 55 DPL 3 1 — — — — 21 10 1 36 ACE 6 — — — — — 15 9 1 31 Other 25 5 2 2 2 1 6 — — 43 Total $ 153 $ 22 $ 2 $ 3 $ 2 $ 1 $ 6 $ 271 $ 33 $ 51 $ 544 __________ (a) As of September 30, 2021 and December 31, 2020, Generation had a contract liability with ComEd for $27 million and $50 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. As of September 30, 2021 and December 31, 2020, ComEd had a Current Payable to Generation of $76 million and $28 million, respectively, on its Consolidated Balance Sheets, which consisted of Generation’s Current Receivable from ComEd, partially offset by Generation’s contract liability with ComEd.
Noncurrent Receivables from/Payables to affiliates	The following table presents noncurrent receivables from affiliates at ComEd and PECO which are recorded as noncurrent payables to affiliates at Generation: September 30, 2021 December 31, 2020 ComEd $ 2,597 $ 2,541 PECO 546 475
Long Term Debt to Financing Trusts	The following table presents Long-term debt to financing trusts: September 30, 2021 December 31, 2020 Exelon ComEd PECO Exelon ComEd PECO ComEd Financing III $ 206 $ 205 $ — $ 206 $ 205 $ — PECO Trust III 81 — 81 81 — 81 PECO Trust IV 103 — 103 103 — 103 Total $ 390 $ 205 $ 184 $ 390 $ 205 $ 184

Mergers, Acquisitions, and Di_3

Mergers, Acquisitions, and Dispositions - Narrative (Details) $ in Millions	Aug. 06, 2021USD ($)	Apr. 01, 2014USD ($)	Sep. 30, 2021USD ($)	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)MW	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020
Business Acquisitions
Acquisition of CENG noncontrolling interest			$ (885)			$ 885	$ 0
Deferred Tax Liability Adjustment - Noncontrolling Interest			$ (290)
Business Dispositions
Gain (Loss) on Sale of Assets and Asset Impairment Charges						$ 147	16
CENG [Member]
Business Acquisitions
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%		49.99%			49.99%		49.99%
Solar Business
Business Dispositions
Capacity Of Facility Of Company Owned Solar Distribution Generation Facilities \| MW					360
Disposal Group, Including Discontinued Operation, Consideration					$ 810
Proceeds from Divestiture of Businesses					675
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent					125
Gain (Loss) on Sale of Assets and Asset Impairment Charges					$ 68
Albany Green Energy biomass facility
Business Dispositions
Disposal Group, Including Discontinued Operation, Consideration				$ 36
Impairment of Long-Lived Assets to be Disposed of				140
Exelon Generation Co L L C [Member]
Business Acquisitions
Acquisition of CENG noncontrolling interest			$ (885)			$ 885	0
Deferred Tax Liability Adjustment - Noncontrolling Interest			$ (288)
Business Dispositions
Gain (Loss) on Sale of Assets and Asset Impairment Charges						$ 144	$ 12
Exelon Generation Co L L C [Member] \| CENG [Member]
Business Acquisitions
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%		49.99%			49.99%		49.99%
Exelon Generation Co L L C [Member] \| Solar Business
Business Dispositions
Capacity Of Facility Of Company Owned Solar Distribution Generation Facilities \| MW					360
Disposal Group, Including Discontinued Operation, Consideration					$ 810
Proceeds from Divestiture of Businesses					675
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent					125
Gain (Loss) on Sale of Assets and Asset Impairment Charges					$ 68
Exelon Generation Co L L C [Member] \| Albany Green Energy biomass facility
Business Dispositions
Disposal Group, Including Discontinued Operation, Consideration				36
Impairment of Long-Lived Assets to be Disposed of				$ 140
CENG [Member]
Business Acquisitions
Equity Method Investment, Ownership Percentage	50.01%		50.01%			50.01%		50.01%
Payments of Capital Distribution		$ 400
Due from Affiliates		400
CENG Preferred Distribution Return						8.50%
Acquisition of CENG noncontrolling interest	$ 885		$ 1,080			$ 1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest			$ (290)			$ (290)
CENG [Member] \| Nine Mile Point
Business Acquisitions
Equity Method Investment, Ownership Percentage			82.00%			82.00%
CENG [Member] \| Exelon Generation Co L L C [Member]
Business Acquisitions
Equity Method Investment, Ownership Percentage	50.01%		50.01%			50.01%		50.01%
Payments of Capital Distribution		400
Due from Affiliates		$ 400
CENG Preferred Distribution Return						8.50%
Acquisition of CENG noncontrolling interest	$ 885		$ 1,080			$ 1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest			$ (288)			$ (288)
CENG [Member] \| Exelon Generation Co L L C [Member] \| Nine Mile Point
Business Acquisitions
Equity Method Investment, Ownership Percentage			82.00%			82.00%

Mergers, Acquisitions, and Di_4

Mergers, Acquisitions, and Dispositions - Changes in Ownership Equity (Details) - USD ($) $ in Millions	Aug. 06, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Changes in Ownership Interest [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic		$ 1,203	$ 501	$ 1,315	$ 1,604
Acquisition of CENG noncontrolling interest		(885)		885	0
Deferred Tax Liability Adjustment - Noncontrolling Interest		(290)
Change from net income (loss) attributable to ownership interest and transfers from Noncontrolling Interest		$ 1,993		$ 2,105
CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%		49.99%		49.99%
Exelon Generation Co L L C [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest		$ (885)		$ 885	0
Deferred Tax Liability Adjustment - Noncontrolling Interest		(288)
Change from net income (loss) attributable to ownership interest and transfers from Noncontrolling Interest		1,399		545
Net Income (Loss) Attributable to Parent		$ 607	$ 49	$ (247)	$ 570
Exelon Generation Co L L C [Member] \| CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%		49.99%		49.99%
CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest	$ 885	$ 1,080		$ 1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest		(290)		(290)
CENG [Member] \| Exelon Generation Co L L C [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest	$ 885	1,080		1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest		$ (288)		$ (288)

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details)	Sep. 23, 2021USD ($)	Jul. 15, 2021	Feb. 15, 2021USD ($)	Sep. 30, 2021USD ($)	Jul. 09, 2021USD ($)	Jul. 02, 2021USD ($)	Aug. 26, 2020USD ($)
Texas-based generating assets
Regulatory Matters Additional Narrative Information [Line Items]
Operating and maintenance				$ 880,000,000
Market Payment Shortfall in Collections				17,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Return on Equity, Percentage		9.33%
Exelon Generation Co L L C [Member] \| ERCOT
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 9,000
Market Payment Shortfall in Collections				3,000,000,000
Market-wide Limit Recovery of Default				2,500,000
Securitized Funds Allocation				2,100,000,000
System-Wide Offer Cap	$ 4,500
Exelon Generation Co L L C [Member] \| Texas-based generating assets
Regulatory Matters Additional Narrative Information [Line Items]
Operating and maintenance				880,000,000
Market Payment Shortfall in Collections				$ 17,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Carbon mitigation credit				54,500,000
Maximum increase of revenue requirement				5.00%
Increase (Decrease) in Regulatory Assets				$ 93,000,000
Commonwealth Edison Co [Member] \| Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Basis points for ComEd's Electric Distribution rates				20
Commonwealth Edison Co [Member] \| Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Basis points for ComEd's Electric Distribution rates				60
Commonwealth Edison Co [Member] \| Electric Distribution Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				$ 47,000,000
Commonwealth Edison Co [Member] \| Energy Efficiency Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				127,000,000
Commonwealth Edison Co [Member] \| Renewable energy swaps
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				(87,000,000)
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				135,000,000
Increase (Decrease) in Regulatory Liabilities				66,000,000
PECO Energy Co [Member] \| Nuclear Decommissioning [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				71,000,000
PECO Energy Co [Member] \| Electric Energy and Natural Gas Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(18,000,000)
PECO Energy Co [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				123,000,000
PECO Energy Co [Member] \| Vacation Accrual
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				14,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds						$ 50,000,000
Increase (Decrease) in Regulatory Liabilities				(116,000,000)
Baltimore Gas and Electric Company [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(128,000,000)
Baltimore Gas and Electric Company [Member] \| Other [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				12,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds						$ 12,000,000
Increase (Decrease) in Regulatory Liabilities				(108,000,000)
Potomac Electric Power Company [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(89,000,000)
Potomac Electric Power Company [Member] \| Electric Transmission Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(19,000,000)
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds					$ 8,000,000
Increase (Decrease) in Regulatory Liabilities				(45,000,000)
Delmarva Power and Light Company [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(41,000,000)
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure							$ 220,000,000
Increase (Decrease) in Regulatory Liabilities				(61,000,000)
Atlantic City Electric Company [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(67,000,000)
Atlantic City Electric Company [Member] \| Stranded Costs
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				$ 14,000,000

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Completed Rate Cases (Details) - USD ($) $ in Millions

Sep. 15, 2021

Jul. 14, 2021

Jun. 28, 2021

Jun. 22, 2021

Jun. 08, 2021

Mar. 31, 2021

Feb. 26, 2021

Feb. 02, 2021

Dec. 16, 2020

Dec. 09, 2020

Sep. 30, 2020

Sep. 11, 2020

Jun. 01, 2020

Apr. 16, 2020

Commonwealth Edison Co [Member] | Illinois 2020 Electric Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ (11)

Approved Revenue Requirement Increase (Decrease)

$ (14)

Approved Return on Equity, Percentage

8.38%

Public Utilities Requested Rate Increase (Decrease), Prior Year Annual Reconciliation

$ (64)

Public Utilities, Approved Equity Capital Structure, Percentage

6.28%

Basis points for ComEd's Revenue Requirement

580

Commonwealth Edison Co [Member] | Illinois 2020 Electric Distribution Base Rate Case [Member] | 2021

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 50

PECO Energy Co [Member] | Pennsylvania 2020 Natural Gas Distribution Base Rate Case

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 69

Approved Revenue Requirement Increase (Decrease)

$ 29

Approved Return on Equity, Percentage

10.24%

Baltimore Gas and Electric Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 203

Approved Revenue Requirement Increase (Decrease)

$ 140

Approved Return on Equity, Percentage

9.50%

Baltimore Gas and Electric Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | 2021

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 59

Baltimore Gas and Electric Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | 2022

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

Baltimore Gas and Electric Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | 2023

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

Baltimore Gas and Electric Company [Member] | Maryland 2020 Gas Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 108

Approved Revenue Requirement Increase (Decrease)

$ 74

Approved Return on Equity, Percentage

9.65%

Baltimore Gas and Electric Company [Member] | Maryland 2020 Gas Distribution Base Rate Case [Member] | 2021

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 53

Baltimore Gas and Electric Company [Member] | Maryland 2020 Gas Distribution Base Rate Case [Member] | 2022

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

Baltimore Gas and Electric Company [Member] | Maryland 2020 Gas Distribution Base Rate Case [Member] | 2023

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 10

Potomac Electric Power Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 104

Approved Revenue Requirement Increase (Decrease)

$ 52

Approved Return on Equity, Percentage

9.55%

Potomac Electric Power Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | March 31, 2022

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 21

Potomac Electric Power Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | March 31, 2023

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

Potomac Electric Power Company [Member] | Maryland 2020 Electric Distribution Base Rate Case [Member] | March 31, 2024

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 15

Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 136

Approved Revenue Requirement Increase (Decrease)

$ 109

Approved Return on Equity, Percentage

9.275%

Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member] | 2021

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 42

Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member] | 2021 | Offsets

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

(22)

Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member] | 2022

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member] | 2022 | Offsets

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ (40)

Delmarva Power and Light Company [Member] | Delaware 2020 Electric Distribution Base Rate Case [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 23

Approved Revenue Requirement Increase (Decrease)

$ 14

Approved Return on Equity, Percentage

9.60%

Atlantic City Electric Company [Member] | New Jersey 2020 Electric Distribution Base Rate Case

Regulatory Matters Completed Rate Cases [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 67

Approved Revenue Requirement Increase (Decrease)

$ 41

Approved Return on Equity, Percentage

9.60%

Atlantic City Electric Company [Member] | New Jersey 2020 Electric Distribution Base Rate Case | Tax Benefits

Regulatory Matters Completed Rate Cases [Line Items]

Approved Revenue Requirement Increase (Decrease)

$ 11

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Pending Rate Cases (Details) - USD ($) $ in Millions	Sep. 01, 2021	Apr. 16, 2021	Mar. 30, 2021
Commonwealth Edison Co [Member] \| Illinois 2021 Electric Distribution Base Rate Case
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ 51
Requested Return on Equity, Percentage		7.36%
Public Utilities, Requested Rate Increase (Decrease), Initial Revenue Requirement, Amount		$ 40
Public Utilities Requested Rate Increase (Decrease), Prior Year Annual Reconciliation		$ 11
Requested Return on Distribution Rate Base, Percentage		5.72%
Basis points for ComEd's Revenue Requirement		580
Commonwealth Edison Co [Member] \| Illinois 2021 Electric Distribution Base Rate Case 2020 Reconciliation
Regulatory Matters Pending Rate Cases [Line Items]
Requested Return on Equity, Percentage		7.29%
Requested Return on Distribution Rate Base, Percentage		5.69%
Basis points for ComEd's Revenue Requirement		580
Commonwealth Edison Co [Member] \| Illinois 2021 Electric Distribution Base Rate Case 2020 Reconciliation \| Performance Metrics Penalty
Regulatory Matters Pending Rate Cases [Line Items]
Basis points for ComEd's Revenue Requirement		7
PECO Energy Co [Member] \| Pennsylvania 2021 Electric Distribution Base Rate Case
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)			$ 246
Requested Return on Equity, Percentage			10.95%
Delmarva Power and Light Company [Member] \| Maryland 2021 Electric Distribution Base Rate Case
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)	$ 29
Requested Return on Equity, Percentage	10.10%

Regulatory Matters - Annual Ele

Regulatory Matters - Annual Electric Transmission Fillings (Details) - 2021 Transmission Formula Rate Annual Update [Domain] - USD ($) $ in Millions	May 28, 2021	May 14, 2021	May 10, 2021	Apr. 16, 2021
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 33
Annual Reconciliation Increase				12
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount				$ 45
Public Utilities, Approved Equity Capital Structure, Percentage				8.20%
Public Utilities, Approved Return on Equity, Percentage				11.50%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint				55.00%
PECO Energy Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ (2)
Annual Reconciliation Increase	26
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 24
Public Utilities, Approved Equity Capital Structure, Percentage	7.37%
Public Utilities, Approved Return on Equity, Percentage	10.35%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint	55.75%
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 38
Annual Reconciliation Increase			27
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 65
Public Utilities, Approved Equity Capital Structure, Percentage			7.35%
Public Utilities, Approved Return on Equity, Percentage			10.50%
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ (9)
Annual Reconciliation Increase		21
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 12
Public Utilities, Approved Equity Capital Structure, Percentage		7.68%
Public Utilities, Approved Return on Equity, Percentage		10.50%
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 19
Annual Reconciliation Increase		33
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 52
Public Utilities, Approved Equity Capital Structure, Percentage		7.20%
Public Utilities, Approved Return on Equity, Percentage		10.50%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 27
Annual Reconciliation Increase		24
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 51
Public Utilities, Approved Equity Capital Structure, Percentage		7.45%
Public Utilities, Approved Return on Equity, Percentage		10.50%

Regulatory Matters - Energy Eff

Regulatory Matters - Energy Efficiency Formula Rate (Details) - Commonwealth Edison Co [Member] - ComEd 2020 Energy Efficiency Formula Rate [Domain] - USD ($) $ in Millions	Jun. 01, 2021	Dec. 31, 2020
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 55
Revenue	(1)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 54
Public Utilities, Requested Equity Capital Structure, Percentage	5.72%
Requested Return on Equity, Percentage	7.36%
Basis points for ComEd's Revenue Requirement	580
Public Utilities, Approved Equity Capital Structure, Percentage		6.26%
Public Utilities, Approved Return on Equity, Percentage		8.46%

Regulatory Matters - Capitalize

Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 44	$ 51
Commonwealth Edison Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	0	(1)
PECO Energy Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	0	0
Baltimore Gas and Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	39	45
Pepco Holdings LLC [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	5	7
Potomac Electric Power Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	3	4
Delmarva Power and Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	2	3
Atlantic City Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 0	$ 0

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Change in Contract with Customer, Asset and Liability (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	$ 150	$ 153	$ 144	$ 159	$ 172	$ 174	$ 144	$ 174
Consideration (received) due, contract assets	(15)	(12)	(16)	(18)	(26)	(19)
Revenues recognized, contract assets	14	9	13	19	13	17
Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination			12
Ending Balance - Contract Assets	149	150	153	160	159	172	149	160
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	132	147	151	20	29	33	151	33
Consideration received (due), contract liabilities	31	17	20	154	13	20
Revenues recognized, contract liabilities	(26)	(32)	(27)	(25)	(22)	(24)
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			3
Ending Balance - Contract Liabilities	137	132	147	149	20	29	137	149
Contract with Customer, Performance Obligation Satisfied in Previous Period	4			2			38	25
Exelon Generation Co L L C [Member]
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	150	153	144	159	172	174	144	174
Consideration (received) due, contract assets	(15)	(12)	(16)	(18)	(26)	(19)
Revenues recognized, contract assets	14	9	13	19	13	17
Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination			12
Ending Balance - Contract Assets	149	150	153	160	159	172	149	160
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	25	54	84	27	56	71	84	71
Consideration received (due), contract liabilities	93	39	31	94	34	55
Revenues recognized, contract liabilities	(65)	(68)	(64)	(65)	(63)	(70)
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			3
Ending Balance - Contract Liabilities	53	25	54	56	27	56	53	56
Contract with Customer, Performance Obligation Satisfied in Previous Period	2			2			81	63
Pepco Holdings LLC [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	113	116	118	0	0	0	118	0
Consideration received (due), contract liabilities	0	0	0	124	0	0
Revenues recognized, contract liabilities	(2)	(3)	(2)	(2)	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			0
Ending Balance - Contract Liabilities	111	113	116	122	0	0	111	122
Contract with Customer, Performance Obligation Satisfied in Previous Period	2			0			7	0
Potomac Electric Power Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	91	92	94	0	0	0	94	0
Consideration received (due), contract liabilities	0	0	0	98	0	0
Revenues recognized, contract liabilities	(2)	(1)	(2)	(2)	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			0
Ending Balance - Contract Liabilities	89	91	92	96	0	0	89	96
Contract with Customer, Performance Obligation Satisfied in Previous Period	2			0			5	0
Delmarva Power and Light Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	11	12	12	0	0	0	12	0
Consideration received (due), contract liabilities	0	0	0	13	0	0
Revenues recognized, contract liabilities	0	(1)	0	0	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			0
Ending Balance - Contract Liabilities	11	11	12	13	0	0	11	13
Contract with Customer, Performance Obligation Satisfied in Previous Period	0			0			1	0
Atlantic City Electric Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	11	12	12	0	0	0	12	0
Consideration received (due), contract liabilities	0	0	0	13	0	0
Revenues recognized, contract liabilities	0	(1)	0	0	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination			0
Ending Balance - Contract Liabilities	11	$ 11	$ 12	13	$ 0	$ 0	11	13
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 0			$ 0			$ 1	$ 0

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Sep. 30, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 476
Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	679
Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	111
Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	89
Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	11
Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	11
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 82
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 168
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 \| Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 \| Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 \| Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 125
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 281
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 50
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 92
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 35
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 41
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 184
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 97
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 87
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01 \| Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 70
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01 \| Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01 \| Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
Segment Information - Narrative (Details)	Sep. 30, 2021Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	11
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	5
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	3

Segment Information - Reconcili

Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended						9 Months Ended
		Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues		$ 8,910			$ 8,853			$ 26,715	$ 24,925
Revenue from Related Parties		0			1			0	4
Depreciation and Amortization		1,624			1,289			4,988	3,312
Operating Expenses		7,117			8,087			24,758	22,387
Interest expense, net		397			404			1,180	1,241
Income (Loss) before income taxes		1,406			786			1,675	1,665
Income taxes		174			216			229	141
Net income (loss)		1,229	$ 476	$ (264)	569	$ 574	$ 376	1,441	1,519
Capital expenditures		1,930			1,833			5,970	5,606
Assets	[1]	132,621						132,621		$ 129,317
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,406			4,659			14,117	13,272
Revenue from Related Parties		324			331			872	932
Income (Loss) before income taxes		814			219			(8)	532
Income taxes		177			100			108	41
Net income (loss)		633	13	(769)	117	529	(161)	(122)	485
Capital expenditures								1,086	1,212
Assets	[2]	48,010						48,010		48,094
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		1,470			1,368			3,854	3,554
Revenue from Related Parties		3			6			10	13
Income (Loss) before income taxes		264			215			538	340
Income taxes		(2)			(1)			3	(77)
Net income (loss)		266	$ 141	$ 128	216	$ 94	$ 108	535	418
Capital expenditures								1,299	1,072
Assets	[3]	24,502						24,502		23,736
Commonwealth Edison Co Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		96			71			249	241
PECO Energy Co Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		59			68			142	146
Baltimore Gas And Electric Company Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		65			84			195	252
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(877)			(845)			(2,470)	(2,430)
Revenue from Related Parties		(876)			(845)			(2,469)	(2,430)
Depreciation and Amortization		0			0			1	0
Operating Expenses		(858)			(833)			(2,407)	(2,397)
Interest expense, net		0			0			(1)	0
Income (Loss) before income taxes		0			0			1	0
Income taxes		0			0			0	0
Net income (loss)		0			0			1	0
Capital expenditures		0			0			0	0
Assets		(10,210)						(10,210)		(10,165)
Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		(93)			(91)			(283)	(281)
Revenue from Related Parties		(93)			(91)			(283)	(281)
Depreciation and Amortization		0			0			0	0
Operating Expenses		(93)			(91)			(283)	(281)
Interest expense, net		0			0			0	0
Income (Loss) before income taxes		0			0			0	0
Income taxes		0			0			0	0
Net income (loss)		0			0			0	0
Capital expenditures		0			0			0	0
Assets		(50)						(50)		(33)
Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		4,406			4,659			14,117	13,272
Depreciation and Amortization		866			558			2,735	1,161
Operating Expenses		3,465			4,727			14,605	12,674
Interest expense, net		77			80			225	277
Income (Loss) before income taxes		814			219			(8)	532
Income taxes		177			100			108	41
Net income (loss)		633			117			(122)	485
Capital expenditures		367			282			1,086	1,212
Assets		48,010						48,010		48,094
Exelon Generation Co L L C [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		324			331			872	932
Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		1,789			1,643			4,840	4,499
Depreciation and Amortization		304			294			893	841
Operating Expenses		1,428			1,302			3,833	3,798
Interest expense, net		98			95			292	287
Income (Loss) before income taxes		276			256			750	446
Income taxes		56			60			141	142
Net income (loss)		220			196			609	304
Capital expenditures		561			554			1,723	1,583
Assets		36,002						36,002		34,466
Commonwealth Edison Co [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		9			15			19	31
PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		818			813			2,399	2,306
Depreciation and Amortization		86			85			259	259
Operating Expenses		677			658			1,908	1,900
Interest expense, net		40			39			119	108
Income (Loss) before income taxes		108			122			392	310
Income taxes		(3)			(16)			9	(7)
Net income (loss)		111			138			383	317
Capital expenditures		301			312			878	824
Assets		13,733						13,733		12,531
PECO Energy Co [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2			3			6	7
Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		770			731			2,426	2,284
Depreciation and Amortization		142			133			434	405
Operating Expenses		709			642			2,080	1,903
Interest expense, net		36			34			103	99
Income (Loss) before income taxes		32			61			266	299
Income taxes		(4)			8			(24)	26
Net income (loss)		36			53			290	273
Capital expenditures		287			290			907	838
Assets		12,197						12,197		11,650
Baltimore Gas and Electric Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		7			6			20	16
Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		1,470			1,368			3,854	3,554
Depreciation and Amortization		210			200			614	585
Operating Expenses		1,155			1,102			3,167	3,057
Interest expense, net		67			67			201	201
Income (Loss) before income taxes		264			215			538	340
Income taxes		(2)			(1)			3	(77)
Net income (loss)		266			216			535	418
Capital expenditures		410			386			1,299	1,072
Assets		24,502						24,502		23,736
Pepco Holdings LLC [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3			6			10	13
Potomac Electric Power Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		660			611			1,736	1,650
Depreciation and Amortization		104			96			302	282
Operating Expenses		501			465			1,396	1,364
Interest expense, net		35			35			104	103
Income (Loss) before income taxes		136			121			273	211
Income taxes		6			3			9	(16)
Net income (loss)		130			118			264	227
Capital expenditures		202			188			641	512
Assets		9,748						9,748		9,264
Potomac Electric Power Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2			3			4	6
Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		360			337			1,040	954
Depreciation and Amortization		53			48			157	143
Operating Expenses		295			296			858	843
Interest expense, net		15			15			47	47
Income (Loss) before income taxes		53			28			144	71
Income taxes		3			1			9	(20)
Net income (loss)		50			27			135	91
Capital expenditures		109			94			320	278
Assets		5,295						5,295		5,140
Delmarva Power and Light Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2			3			6	7
Atlantic City Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		451			420			1,080	952
Depreciation and Amortization		46			48			133	134
Operating Expenses		359			338			911	847
Interest expense, net		14			15			43	45
Income (Loss) before income taxes		79			68			129	67
Income taxes		(11)			(7)			(12)	(39)
Net income (loss)		90			75			141	106
Capital expenditures		97			103			336	281
Assets		4,532						4,532		4,286
Atlantic City Electric Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1			1			2	3
Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues		534			484			1,549	1,440
Depreciation and Amortization		16			19			52	61
Operating Expenses		541			489			1,572	1,452
Interest expense, net		79			89			241	269
Income (Loss) before income taxes		(88)			(87)			(264)	(262)
Income taxes		(50)			65			(8)	16
Net income (loss)		(37)			(151)			(255)	(278)
Capital expenditures		4			9			77	77
Assets		8,387						8,387		9,005
Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		92			91			281	279
Depreciation and Amortization		7			8			22	26
Operating Expenses		93			94			285	284
Interest expense, net		3			2			7	6
Income (Loss) before income taxes		(4)			(2)			(8)	(9)
Income taxes		0			2			(3)	(2)
Net income (loss)		(4)			(4)			(5)	(6)
Capital expenditures		2			1			2	1
Assets		4,977						4,977		$ 5,079
Corporate and Other [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		531			485			1,542	1,435
Corporate and Other [Member] \| Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		91			90			281	278
Competitive businesses electric revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,011			3,875			11,404	10,447
Competitive businesses electric revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(319)			(326)			(860)	(920)
Competitive businesses electric revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,330			4,201			12,264	11,367
Competitive businesses electric revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses electric revenues [Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses electric revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses electric revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses natural gas revenues Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		575			323			2,408	1,345
Competitive businesses natural gas revenues Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	(3)
Competitive businesses natural gas revenues Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		575			323			2,408	1,348
Competitive businesses natural gas revenues Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses natural gas revenues Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses natural gas revenues Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses natural gas revenues Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses natural gas revenues Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Competitive businesses other revenues [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(502)			132			(564)	552
Competitive businesses other revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(3)			(3)			(9)	(5)
Competitive businesses other revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(499)			135			(555)	557
Competitive businesses other revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Competitive businesses other revenues [Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Competitive businesses other revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Competitive businesses other revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Competitive businesses other revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Rate-regulated electric revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,657			4,365			12,432	11,585
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,438			1,308			3,632	3,440
Rate-regulated electric revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(15)			(22)			(33)	(50)
Rate-regulated electric revenues [Member] \| Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(4)			(6)			(12)	(15)
Rate-regulated electric revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,789			1,643			4,840	4,499
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		762			759			2,033	1,948
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		677			646			1,866	1,763
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,444			1,339			3,726	3,425
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		660			611			1,736	1,650
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		337			314			922	838
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		451			420			1,080	952
Rate-regulated electric revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated electric revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		169			159			1,035	990
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			23			118	116
Rate-regulated natural gas revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(3)			(3)			(9)	(5)
Rate-regulated natural gas revenues [Member] \| Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		56			54			366	358
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		93			85			560	521
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			23			118	116
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			23			118	116
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Rate-regulated natural gas revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			(1)			0	6
Shared service and other revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(537)			(491)			(1,559)	(1,447)
Shared service and other revenues [Member] \| Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(89)			(85)			(271)	(266)
Shared service and other revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3			6			10	13
Shared service and other revenues [Member] \| Potomac Electric Power Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Atlantic City Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Shared service and other revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		534			484			1,549	1,440
Shared service and other revenues [Member] \| Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		$ 92			$ 91			$ 281	$ 279

[1]	Exelon’s consolidated assets include $2,722 million and $10,200 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $1,088 million and $3,598 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 17 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $2,704 million and $10,182 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $1,078 million and $3,572 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 17 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both September 30, 2021 and December 31, 2020 of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $10 million and $26 million at September 30, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 17 — Variable Interest Entities for additional information.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 8,910	$ 8,853	$ 26,715	$ 24,925
Revenue from Related Parties	0	1	0	4
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,272	1,313	3,527	3,561
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	985	1,043	2,945	3,007
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	455	406	1,173	1,061
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	358	330	890	754
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,260	1,109	3,729	2,984
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,330	4,201	12,264	11,367
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	575	323	2,408	1,348
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(499)	135	(555)	557
Unrealized Gain (Loss) on Securities	(635)	37	(958)	238
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,406	4,659	14,117	13,272
Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,268	1,307	3,511	3,540
Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	985	1,042	2,944	3,013
Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	455	406	1,174	1,062
Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	356	323	879	734
Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,266	1,123	3,756	3,018
Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,330	4,201	12,264	11,367
Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	575	323	2,408	1,348
Operating Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	754	255	1,242	472
Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,406	4,659	14,117	13,272
Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(499)	135	(555)	557
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(877)	(845)	(2,470)	(2,430)
Revenue from Related Parties	(876)	(845)	(2,469)	(2,430)
Intersegment Eliminations [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	4	6	16	21
Intersegment Eliminations [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	1	1	(6)
Intersegment Eliminations [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	(1)	(1)
Intersegment Eliminations [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	2	7	11	20
Intersegment Eliminations [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(6)	(14)	(27)	(34)
Intersegment Eliminations [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Intersegment Eliminations [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Intersegment Eliminations [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Intersegment Eliminations [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,145	1,327	3,377	3,692
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,084	974	3,067	2,773
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	445	401	1,204	1,074
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	191	249	724	579
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	948	937	3,043	2,718
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,813	3,888	11,415	10,836
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	266	169	1,384	881
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,174	4,142	13,090	11,985
Revenue from Contract with Customer [Member] \| Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	95	85	291	268
Other [Member] \| Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	123	(20)	134	(152)
Other [Member] \| Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(99)	68	(123)	240
Other [Member] \| Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	10	5	(30)	(12)
Other [Member] \| Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	165	74	155	155
Other [Member] \| Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	318	186	713	300
Other [Member] \| Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	517	313	849	531
Other [Member] \| Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	309	154	1,024	467
Other [Member] \| Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	232	517	1,027	1,287
Other [Member] \| Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ (594)	$ 50	$ (846)	$ 289

Segment Information - Generat_2

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 570	$ 591	$ 1,712	$ 1,683
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	655	750	2,015	2,178
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	346	285	880	725
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	179	147	(922)	325
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	211	225	564	538
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	1,961	1,998	4,249	5,449
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	899	347	1,765	862
Unrealized Gain (Loss) on Securities	(635)	37	(958)	238
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,860	2,345	6,014	6,311
Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
RNF from external customers	567	586	1,698	1,660
Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
RNF from external customers	655	748	2,014	2,180
Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
RNF from external customers	343	281	873	714
Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
RNF from external customers	181	141	(775)	311
Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
RNF from external customers	233	253	641	608
Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
RNF from external customers	1,979	2,009	4,451	5,473
Operating Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	881	336	1,563	838
Unrealized Gain (Loss) on Securities	754	255	1,242	472
Accelerated nuclear fuel amortization	42	24	148	24
Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,860	2,345	6,014	6,311
Intersegment Eliminations [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	3	5	14	23
Intersegment Eliminations [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0	2	1	(2)
Intersegment Eliminations [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	3	4	7	11
Intersegment Eliminations [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(2)	6	(147)	14
Intersegment Eliminations [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(22)	(28)	(77)	(70)
Intersegment Eliminations [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(18)	(11)	(202)	(24)
Intersegment Eliminations [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	18	11	202	24
Intersegment Eliminations [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0	$ 0	$ 0	$ 0

Segment Information - Electric

Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue, Major Customer [Line Items]
Revenues	$ 8,910	$ 8,853	$ 26,715	$ 24,925
Revenue from Related Parties	0	1	0	4
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,789	1,643	4,840	4,499
Revenue from Related Parties	9	15	19	31
Commonwealth Edison Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,815	1,678	4,784	4,540
Commonwealth Edison Co [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(26)	(35)	56	(41)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	818	813	2,399	2,306
Revenue from Related Parties	2	3	6	7
PECO Energy Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	813	808	2,377	2,293
PECO Energy Co [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	5	5	22	13
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	770	731	2,426	2,284
Revenue from Related Parties	7	6	20	16
Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	790	740	2,434	2,290
Baltimore Gas and Electric Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(20)	(9)	(8)	(6)
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,470	1,368	3,854	3,554
Revenue from Related Parties	3	6	10	13
Pepco Holdings LLC [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,462	1,337	3,757	3,567
Pepco Holdings LLC [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	8	31	97	(13)
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	660	611	1,736	1,650
Revenue from Related Parties	2	3	4	6
Potomac Electric Power Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	650	593	1,680	1,629
Potomac Electric Power Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	10	18	56	21
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	360	337	1,040	954
Revenue from Related Parties	2	3	6	7
Delmarva Power and Light Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	361	329	1,022	968
Delmarva Power and Light Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)	8	18	(14)
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	451	420	1,080	952
Revenue from Related Parties	1	1	2	3
Atlantic City Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	451	415	1,057	972
Atlantic City Electric Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	0	5	23	(20)
Rate-regulated electric revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,657	4,365	12,432	11,585
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,812	1,666	4,789	4,519
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,815	1,678	4,784	4,540
Revenue from Related Parties	9	15	19	31
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6	3	24	10
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	978	920	2,479	2,389
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	433	379	1,176	1,067
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	148	135	420	388
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11	10	33	33
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	245	234	676	663
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	757	751	2,008	1,931
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	757	753	2,011	1,934
Revenue from Related Parties	2	3	5	6
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	0	2	3
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	509	518	1,325	1,277
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	113	104	312	291
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	67	66	183	174
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7	7	24	21
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	61	58	167	171
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	694	649	1,874	1,775
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	695	652	1,877	1,781
Revenue from Related Parties	4	3	10	9
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	0	7	3
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	383	389	1,044	1,034
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	73	65	202	183
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	128	113	342	311
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7	7	20	20
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	104	78	269	233
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,438	1,308	3,632	3,440
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,439	1,314	3,639	3,451
Revenue from Related Parties	3	6	10	13
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	0	3	2
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	782	763	1,924	1,825
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	150	134	392	355
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	320	262	825	755
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	15	14	45	45
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	172	141	453	471
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	649	590	1,678	1,624
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	650	593	1,680	1,629
Revenue from Related Parties	2	3	4	6
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	0	2	1
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	309	307	785	779
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	36	36	101	101
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	244	195	616	558
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8	8	24	25
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	53	47	154	166
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	337	303	899	846
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	338	306	904	852
Revenue from Related Parties	2	3	6	7
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	0	1	1
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	198	193	535	501
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	53	45	145	127
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	27	21	70	66
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	11	10
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	56	44	143	148
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	450	414	1,055	969
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	451	415	1,057	972
Revenue from Related Parties	1	1	2	3
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	275	263	604	545
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	61	53	146	127
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	49	46	139	131
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	63	50	158	159
Rate-regulated natural gas revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	169	159	1,035	990
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	56	54	365	358
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	56	55	366	359
Revenue from Related Parties	0	0	1	1
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	36	32	251	252
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13	16	94	86
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	6	17	18
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	1	4	3
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	93	85	549	503
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	95	88	557	509
Revenue from Related Parties	3	3	10	7
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	0	2	1
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	57	55	354	342
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10	9	59	55
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	22	21	103	96
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6	3	41	16
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	23	118	116
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	23	118	116
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10	11	67	68
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	6	29	30
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	1	5	3
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	11	10
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	2	6	5
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	23	118	116
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	23	118	116
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10	11	67	68
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	6	29	30
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	1	5	3
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	11	10
Rate-regulated natural gas revenues [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	2	6	5
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alternative revenue programs [Member] \| Commonwealth Edison Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(32)	(38)	32	(51)
Alternative revenue programs [Member] \| PECO Energy Co [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	5	20	10
Alternative revenue programs [Member] \| Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(24)	(9)	(17)	(10)
Alternative revenue programs [Member] \| Pepco Holdings LLC [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6	31	94	(15)
Alternative revenue programs [Member] \| Potomac Electric Power Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	18	54	20
Alternative revenue programs [Member] \| Delmarva Power and Light Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(2)	8	17	(15)
Alternative revenue programs [Member] \| Atlantic City Electric Company [Member] \| Regulated Operation [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 0	$ 5	$ 23	$ (20)

Accounts Receivable - Narrative

Accounts Receivable - Narrative (Details) - Sale of accounts receivable [Member] - USD ($) $ in Millions	Sep. 30, 2021	Jun. 24, 2021	May 24, 2021	Mar. 31, 2021	Feb. 17, 2021	Dec. 31, 2020	Apr. 08, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	$ 1,401					$ 1,139	$ 1,200
Cash proceeds received	900	$ 50			$ 250	500	500
DPP consideration	501					639	650
Cash outflows returned			$ (50)
April 7, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	750
March 29, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	900
Cash proceeds received				$ 150
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	1,401					1,139	1,200
Cash proceeds received	900	$ 50			$ 250	500	500
DPP consideration	501					$ 639	$ 650
Cash outflows returned			$ (50)
Exelon Generation Co L L C [Member] \| April 7, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	750
Exelon Generation Co L L C [Member] \| March 29, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 900
Cash proceeds received				$ 150

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			$ (155)	$ (130)
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(59)	(16)
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(34)	(23)
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(36)	(38)
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(7)	(12)
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(18)	(41)
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(9)	(24)
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(3)	(15)
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses			(6)	(2)
Customer accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 395	$ 261	366	243
Current period provision for expected credit losses	47	114	122	222
Writeoffs, net of recoveries	33	17	79	51
Allowance change due to sale of customer accounts				56
Ending balance	409	358	409	358
Customer accounts receivable \| Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	75	33	32	80
Current period provision for expected credit losses	10	1	57	13
Writeoffs, net of recoveries	1	1	5	4
Allowance change due to sale of customer accounts				56
Ending balance	84	33	84	33
Customer accounts receivable \| Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	89	72	97	59
Current period provision for expected credit losses	11	37	23	62
Writeoffs, net of recoveries	12	4	32	16
Ending balance	88	105	88	105
Customer accounts receivable \| PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	111	71	116	55
Current period provision for expected credit losses	1	27	7	56
Writeoffs, net of recoveries	11	2	22	15
Ending balance	101	96	101	96
Customer accounts receivable \| Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	27	23	35	12
Current period provision for expected credit losses	7	14	2	28
Writeoffs, net of recoveries	3	2	6	5
Ending balance	31	35	31	35
Customer accounts receivable \| Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	93	62	86	37
Current period provision for expected credit losses	18	35	33	63
Writeoffs, net of recoveries	6	8	14	11
Ending balance	105	89	105	89
Customer accounts receivable \| Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	38	24	32	13
Current period provision for expected credit losses	5	11	15	24
Writeoffs, net of recoveries	2	0	6	2
Ending balance	41	35	41	35
Customer accounts receivable \| Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	19	18	22	11
Current period provision for expected credit losses	3	7	4	14
Writeoffs, net of recoveries	4	3	8	3
Ending balance	18	22	18	22
Customer accounts receivable \| Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	36	20	32	13
Current period provision for expected credit losses	10	17	14	25
Writeoffs, net of recoveries	0	5	0	6
Ending balance	46	32	46	32
Other receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	72	61	71	48
Current period provision for expected credit losses	9	15	15	36
Writeoffs, net of recoveries	4	1	9	9
Ending balance	77	75	77	75
Other receivables \| Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	1	0	0	0
Current period provision for expected credit losses	3	0	4	0
Writeoffs, net of recoveries	0	0	0	0
Ending balance	4	0	4	0
Other receivables \| Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	18	22	21	20
Current period provision for expected credit losses	2	5	0	9
Writeoffs, net of recoveries	1	0	2	2
Ending balance	19	27	19	27
Other receivables \| PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	7	7	8	7
Current period provision for expected credit losses	1	1	2	3
Writeoffs, net of recoveries	1	1	3	3
Ending balance	7	7	7	7
Other receivables \| Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8	6	9	5
Current period provision for expected credit losses	1	3	2	7
Writeoffs, net of recoveries	1	0	3	3
Ending balance	8	9	8	9
Other receivables \| Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	38	26	33	16
Current period provision for expected credit losses	2	6	7	17
Writeoffs, net of recoveries	0	0	0	1
Ending balance	40	32	40	32
Other receivables \| Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	16	11	13	7
Current period provision for expected credit losses	1	2	4	6
Writeoffs, net of recoveries	0	0	0	0
Ending balance	17	13	17	13
Other receivables \| Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	9	7	9	4
Current period provision for expected credit losses	(1)	1	(1)	4
Writeoffs, net of recoveries	0	0	0	0
Ending balance	8	8	8	8
Other receivables \| Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	13	8	11	5
Current period provision for expected credit losses	2	3	4	7
Writeoffs, net of recoveries	0	0	0	1
Ending balance	$ 15	$ 11	$ 15	$ 11

Accounts Receivable - Unbilled

Accounts Receivable - Unbilled Customer Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 941	$ 998
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	359	258
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	224	218
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	113	147
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	98	197
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	147	178
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	70	87
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	34	62
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 43	$ 29

Accounts Receivable - Purchases

Accounts Receivable - Purchases and Sales of Accounts Receivable (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 24, 2021	Feb. 17, 2021	Dec. 31, 2020	Apr. 08, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loss on sale receivables	$ 1	$ 8	$ 26	$ 23
Proceeds from new transfers			4,440	1,889
Cash collections received on deferred purchase price and reinvested in the Facility			2,652	2,518
Cash collections reinvested in the Facility			7,092	4,407
Accounts Receivable, Purchase			2,945	2,698
Accounts Receivable, Sale			100	542
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loss on sale receivables	1	$ 8	26	23
Proceeds from new transfers			4,440	1,889
Cash collections received on deferred purchase price and reinvested in the Facility			2,652	2,518
Cash collections reinvested in the Facility			7,092	4,407
Accounts Receivable, Purchase			0	0
Accounts Receivable, Sale			117	790
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			810	865
Accounts Receivable, Sale			0	0
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			795	786
Accounts Receivable, Sale			0	0
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			531	508
Accounts Receivable, Sale			0	0
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			826	787
Accounts Receivable, Sale			0	0
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			504	484
Accounts Receivable, Sale			0	0
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			166	160
Accounts Receivable, Sale			0	0
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase			156	143
Accounts Receivable, Sale			0	0
Exelon Generation Co LLC Affiliate [Member] \| Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	34
Exelon Generation Co LLC Affiliate [Member] \| PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	67
Exelon Generation Co LLC Affiliate [Member] \| Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			17	75
Exelon Generation Co LLC Affiliate [Member] \| Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	72
Exelon Generation Co LLC Affiliate [Member] \| Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	51
Exelon Generation Co LLC Affiliate [Member] \| Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	13
Exelon Generation Co LLC Affiliate [Member] \| Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase			0	8
Exelon Utility Registrants Affiliates [Member] \| Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Related Parties, Sale			17	248
Sale of accounts receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	1,401		1,401				$ 1,139	$ 1,200
Cash proceeds received	900		900		$ 50	$ 250	500	500
DPP consideration	501		501				639	650
Transfer of Financial Assets Accounted for as Sales, Additional Transfers			7,373	4,515
Sale of accounts receivable [Member] \| Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	1,401		1,401				1,139	1,200
Cash proceeds received	900		900		$ 50	$ 250	500	500
DPP consideration	501		501				$ 639	$ 650
Transfer of Financial Assets Accounted for as Sales, Additional Transfers			7,373	$ 4,515
Sale of Accounts Receivable_Three Months Ended Q1 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cash proceeds received	400		400
Sale of Accounts Receivable_Three Months Ended Q1 2021 \| Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cash proceeds received	$ 400		$ 400

Early Plant Retirements - Narra

Early Plant Retirements - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
Early Plant Retirements - Narrative (Details) $ in Millions	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Property, Plant and Equipment [Line Items]
Operating Expenses	$ 7,117	$ 8,087	$ 24,758	$ 22,387
Cost, Depreciation and Amortization	1,624	1,289	4,988	3,312
Generation New England [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			43
Cost, Depreciation and Amortization			41	6
Byron Dresden
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation, Revision of Estimate	(13)
Facility Closing [Member] \| Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Severance Costs	(81)
Facility Closing [Member] \| Byron Dresden
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation, Revision of Estimate	(4)	(34)	(8)	(34)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	866	558	2,735	1,161
Exelon Generation Co L L C [Member] \| Generation New England [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			43
Cost, Depreciation and Amortization			41	6
Exelon Generation Co L L C [Member] \| Byron Dresden
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation, Revision of Estimate	(13)
Exelon Generation Co L L C [Member] \| Facility Closing [Member] \| Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Severance Costs	(81)
Exelon Generation Co L L C [Member] \| Facility Closing [Member] \| Byron Dresden
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation, Revision of Estimate	$ (4)	(34)	$ (8)	(34)
Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Carbon mitigation credit	54,500,000		54,500,000
Cost, Depreciation and Amortization	$ 304	$ 294	$ 893	$ 841

Early Plant Retirements - Preta

Early Plant Retirements - Pretax Expense (Details) - Byron Dresden - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Asset Retirement Obligation, Revision of Estimate	$ (13)
Facility Closing [Member]
Accelerated depreciation	574	$ 254	$ 1,805	$ 254
Accelerated nuclear fuel amortization	42	14	148	14
Operating and maintenance	(94)	220	(94)	220
Asset Retirement Obligation, Revision of Estimate	(4)	(34)	(8)	(34)
Asset Retirement Obligation Contractual Offset	(60)	(129)	(451)	(129)
Restructuring and Related Cost, Incurred Cost	466	393	1,416	393
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Revision of Estimate	(13)
Exelon Generation Co L L C [Member] \| Facility Closing [Member]
Accelerated depreciation	574	254	1,805	254
Accelerated nuclear fuel amortization	42	14	148	14
Operating and maintenance	(94)	220	(94)	220
Asset Retirement Obligation, Revision of Estimate	(4)	(34)	(8)	(34)
Asset Retirement Obligation Contractual Offset	(60)	(129)	(451)	(129)
Restructuring and Related Cost, Incurred Cost	$ 466	$ 393	$ 1,416	$ 393

Nuclear Decommissioning - Narra

Nuclear Decommissioning - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 15,404		$ 15,404		$ 14,464
Increase in PPE related to ARO update			574	$ 775
Nuclear Decommissioning [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Net increase (decrease) due to changes in, and timing of, estimated future cash flows			256
Increase (Decrease) in ARO Due to Reversal of Early Retirement			(170)
Increase (Decrease) in ARO for Impacts of Revised Decommissioning Cost Estimates			(110)
Increase (Decrease) in ARO Due to Updated Cost Escalation Rates and Discount Rates			510
Nuclear Decommissioning [Member] \| Operating Expense [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate			(51)
Nuclear Decommissioning Byron
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Related Activities Not Contractually Offset	140	$ 53
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	15,404		15,404		14,464
Increase in PPE related to ARO update			550	$ 775
Exelon Generation Co L L C [Member] \| Nuclear Decommissioning [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Net increase (decrease) due to changes in, and timing of, estimated future cash flows			256
Increase (Decrease) in ARO Due to Reversal of Early Retirement			(170)
Increase (Decrease) in ARO for Impacts of Revised Decommissioning Cost Estimates			(110)
Increase (Decrease) in ARO Due to Updated Cost Escalation Rates and Discount Rates			510
Exelon Generation Co L L C [Member] \| Nuclear Decommissioning [Member] \| Operating Expense [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate			(51)
Exelon Generation Co L L C [Member] \| Nuclear Decommissioning Byron
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Related Activities Not Contractually Offset	140	$ 53
Assets, Total [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	15,602		15,602		14,599
Assets, Total [Member] \| Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	15,602		15,602		14,599
Other Current Assets [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	198		198		134
Other Current Assets [Member] \| Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 198		$ 198		$ 134

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	$ 383	$ 375
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	383	$ 375
Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	11,922
Accretion expense	375
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	256
Costs incurred related to decommissioning plants	(57)
ARO ending balance	12,496
Current portion of ARO	74		$ 80
Nuclear Decommissioning [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	11,922
Accretion expense	375
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	256
Costs incurred related to decommissioning plants	(57)
ARO ending balance	12,496
Current portion of ARO	$ 74		$ 80

Asset Impairments - Narrative (

Asset Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use				$ 541	$ 567
Net income (loss) attributable to noncontrolling interests	$ 26		$ 68	126	(85)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use				537	552
Net income (loss) attributable to noncontrolling interests	26		68	125	$ (85)
Generation New England [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use		$ 350	500
Generation New England [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use		$ 350	$ 500
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use				0
Midwest Asset Group [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use				$ 0
Contracted Wind Project
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	45
Net income (loss) attributable to noncontrolling interests	21
Contracted Wind Project \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	45
Net income (loss) attributable to noncontrolling interests	$ 21

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Liability Adjustment - Noncontrolling Interest	$ (290)
Income taxes	174	$ 216	$ 229	$ 141
CENG [Member]
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Liability Adjustment - Noncontrolling Interest	290
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Liability Adjustment - Noncontrolling Interest	(288)
Income taxes	177	100	108	41
Exelon Generation Co L L C [Member] \| CENG [Member]
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Liability Adjustment - Noncontrolling Interest	288
Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Income taxes	(11)	$ (7)	(12)	(39)
State and Local Jurisdiction [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Deferred Income Taxes			27	66
Income taxes			27
State and Local Jurisdiction [Member] \| Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Deferred Income Taxes				$ (26)
State and Local Jurisdiction [Member] \| Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 14		$ 14

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.00%	12.30%		3.00%	9.30%
Qualified nuclear decommissioning trust fund income	0.50%	13.20%		9.40%	3.20%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					2.50%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.40%)	(1.40%)		(0.80%)	(1.20%)
Plant basis differences	(1.70%)	(4.30%)		(3.90%)	(4.00%)
Production tax credits and other credits	(1.00%)	(3.00%)		(2.60%)	(2.60%)
Noncontrolling interests	(0.40%)	0.80%		(0.70%)	1.00%
Excess deferred tax amortization	(6.80%)	(10.10%)		(13.90%)	(15.80%)
Tax Settlements		(0.20%)			(5.00%)
Other	(4.80%)	(0.80%)		2.20%	0.10%
Effective income tax rate	12.40%	27.50%		13.70%	8.50%
Decrease in Unrecognized Tax Benefits is Reasonably Possible			$ 411
Tax Adjustments, Settlements, and Unusual Provisions			76
Income Tax Expense (Benefit)	$ (174)	$ (216)		$ (229)	$ (141)
Internal Revenue Service (IRS) [Member]
Increase (decrease) due to:
Income Tax Expense (Benefit)			67
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	4.40%	(10.30%)		90.20%	0.00%
Qualified nuclear decommissioning trust fund income	0.90%	47.40%		(1932.60%)	10.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.70%)	(4.50%)		130.60%	(3.20%)
Plant basis differences	0.00%	0.00%		0.00%	0.00%
Production tax credits and other credits	(1.40%)	(9.20%)		425.10%	(7.00%)
Noncontrolling interests	(0.60%)	2.90%		145.20%	3.10%
Excess deferred tax amortization	0.00%	0.00%		0.00%	0.00%
Tax Settlements		(0.70%)			(15.70%)
Other	(1.90%)	(0.90%)		(229.50%)	(0.50%)
Effective income tax rate	21.70%	45.70%		(1350.00%)	7.70%
Decrease in Unrecognized Tax Benefits is Reasonably Possible			411
Tax Adjustments, Settlements, and Unusual Provisions			73
Income Tax Expense (Benefit)	$ (177)	$ (100)		$ (108)	$ (41)
Exelon Generation Co L L C [Member] \| Internal Revenue Service (IRS) [Member]
Increase (decrease) due to:
Income Tax Expense (Benefit)			$ 67
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	8.00%	8.10%		7.60%	12.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					9.40%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.20%)		(0.10%)	(0.30%)
Plant basis differences	(0.80%)	(0.60%)		(0.70%)	(0.90%)
Production tax credits and other credits	(0.50%)	(0.40%)		(0.50%)	(0.40%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(7.60%)	(5.60%)		(7.20%)	(11.80%)
Tax Settlements		0.00%			0.00%
Other	0.30%	1.10%		(1.30%)	2.10%
Effective income tax rate	20.30%	23.40%		18.80%	31.80%
Income Tax Expense (Benefit)	$ (56)	$ (60)		$ (141)	$ (142)
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(4.10%)	(6.20%)		(2.60%)	(3.40%)
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%		0.00%	0.00%
Plant basis differences	(16.20%)	(23.30%)		(12.60%)	(15.90%)
Production tax credits and other credits	0.00%	0.00%		0.00%	0.00%
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(3.40%)	(3.80%)		(3.30%)	(3.50%)
Tax Settlements		0.00%			0.00%
Other	(0.10%)	(0.80%)		(0.20%)	(0.50%)
Effective income tax rate	(2.80%)	(13.10%)		2.30%	(2.30%)
Income Tax Expense (Benefit)	$ 3	$ 16		$ (9)	$ 7
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(13.00%)	5.10%		(10.80%)	5.50%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)		(0.10%)	(0.10%)
Plant basis differences	(1.40%)	(1.20%)		(1.50%)	(1.80%)
Production tax credits and other credits	(0.90%)	(0.80%)		(0.90%)	(0.40%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(17.30%)	(10.60%)		(16.00%)	(15.00%)
Tax Settlements		0.00%			0.00%
Other	(0.80%)	(0.30%)		(0.70%)	(0.50%)
Effective income tax rate	(12.50%)	13.10%		(9.00%)	8.70%
Income Tax Expense (Benefit)	$ 4	$ (8)		$ 24	$ (26)
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.00%	5.50%		4.60%	5.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.20%)		(0.10%)	(0.20%)
Plant basis differences	(1.30%)	(1.50%)		(1.30%)	(2.20%)
Production tax credits and other credits	(0.50%)	(0.50%)		(0.50%)	(0.30%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(24.90%)	(24.90%)		(22.80%)	(45.30%)
Tax Settlements		0.00%			0.00%
Other	0.00%	0.10%		(0.30%)	(0.60%)
Effective income tax rate	(0.80%)	(0.50%)		0.60%	(22.60%)
Income Tax Expense (Benefit)	$ 2	$ 1		$ (3)	$ 77
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	3.40%	4.60%		2.50%	4.20%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	(0.10%)		0.00%	(0.10%)
Plant basis differences	(2.00%)	(2.10%)		(1.90%)	(2.40%)
Production tax credits and other credits	(0.50%)	(0.50%)		(0.50%)	(0.30%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(17.60%)	(20.00%)		(17.40%)	(29.20%)
Tax Settlements		0.00%			0.00%
Other	0.10%	(0.40%)		(0.40%)	(0.80%)
Effective income tax rate	4.40%	2.50%		3.30%	(7.60%)
Income Tax Expense (Benefit)	$ (6)	$ (3)		$ (9)	$ 16
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.40%	6.60%		6.50%	6.50%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)		(0.20%)	(0.30%)
Plant basis differences	(0.60%)	(0.40%)		(0.70%)	(0.50%)
Production tax credits and other credits	(0.40%)	(0.50%)		(0.40%)	(0.20%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(19.90%)	(23.60%)		(19.70%)	(53.60%)
Tax Settlements		0.00%			0.00%
Other	(0.60%)	0.70%		(0.20%)	(1.10%)
Effective income tax rate	5.70%	3.60%		6.30%	(28.20%)
Income Tax Expense (Benefit)	$ (3)	$ (1)		$ (9)	$ 20
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%		21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	7.00%	6.90%		7.30%	6.80%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments					0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.30%)		(0.20%)	(0.50%)
Plant basis differences	(0.60%)	(1.30%)		(0.60%)	(3.70%)
Production tax credits and other credits	(0.50%)	(0.40%)		(0.50%)	(0.40%)
Noncontrolling interests	0.00%	0.00%		0.00%	0.00%
Excess deferred tax amortization	(41.40%)	(36.80%)		(36.30%)	(81.40%)
Tax Settlements		0.00%			0.00%
Other	0.80%	0.60%		0.00%	0.00%
Effective income tax rate	(13.90%)	(10.30%)		(9.30%)	(58.20%)
Income Tax Expense (Benefit)	$ 11	$ 7		$ 12	$ 39

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Pepco Holdings LLC [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 56	$ 52
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 16	$ 15

Income Taxes - Allocation of Ta

Income Taxes - Allocation of Tax Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Exelon Generation Co L L C [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 64	$ 64
Commonwealth Edison Co [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	1	14
PECO Energy Co [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	19	17
Baltimore Gas and Electric Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	0	0
Pepco Holdings LLC [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	17	17
Potomac Electric Power Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	16	8
Delmarva Power and Light Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	0	6
Atlantic City Electric Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 0	$ 1

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2021	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 33
Increase (Decrease) in Obligation, Other Postretirement Benefits	(9)
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	1
Defined Benefit Plan Amounts Recognized In Regulatory Assets Before Tax	21
Defined Benefit Plan Amounts Recognized In Regulatory Liabilities Before Tax	$ 1
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets		7.00%
Discount rate		2.58%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets		6.46%
Discount rate		2.51%

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amortization of:
Net periodic benefit cost	$ 19	$ 15	$ 64	$ 38
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	110	97	330	290
Interest cost	161	190	481	569
Expected return on assets	(335)	(317)	(1,003)	(953)
Amortization of:
Prior service cost (credit)	1	1	3	3
Actuarial loss	150	128	449	384
Curtailment benefits			0	0
Settlement charges	12	8	16	14
Net periodic benefit cost	99	107	276	307
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	20	22	60	67
Interest cost	29	37	86	114
Expected return on assets	(40)	(41)	(119)	(122)
Amortization of:
Prior service cost (credit)	(8)	(30)	(25)	(92)
Actuarial loss	9	12	27	36
Curtailment benefits			(1)	0
Settlement charges	0	0	0	0
Net periodic benefit cost	$ 10	$ 0	$ 28	$ 3

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			$ 304	$ 310
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 109	$ 107	304	310
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			92	89
Exelon Generation Co L L C [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	36	30	92	89
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			97	85
Commonwealth Edison Co [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	32	29	97	85
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			5	4
PECO Energy Co [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	2	1	5	4
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			45	46
Baltimore Gas and Electric Company [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	16	16	47	47
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			36	52
Pepco Holdings LLC [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	12	17	36	52
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			5	11
Potomac Electric Power Company [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	2	4	5	11
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			2	6
Delmarva Power and Light Company [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	1	2	2	6
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs			8	10
Atlantic City Electric Company [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 3	$ 3	$ 8	$ 10

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 38	$ 37	$ 107	$ 104
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	14	14	40	41
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	9	9	27	25
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	2	3	8	8
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	4	4	8	8
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	5	3	12	9
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	1	1	3	3
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	1	1	3	2
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 1	$ 0	$ 2	$ 1

Derivative Financial Instrume_3

Derivative Financial Instruments - Narrative (Details) MWh in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Jun. 30, 2012MWh	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 3,001	$ 1,432
Other		1,180	1,264
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		3,001	1,432
Other		347	444
Commonwealth Edison Co [Member]
Derivative [Line Items]
Long-term Purchase Commitment, Minimum Energy Volume Required \| MWh	1.3
Other		165	143
PECO Energy Co [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		23
Other		31	30
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		46
Other		81	91
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		11
Other		$ 41	20
Minimum [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		96.00%
Maximum [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		99.00%
Commodity Contract [Member] \| Commonwealth Edison Co [Member] \| External Counterparties \| Collateral [Member]
Derivative [Line Items]
Other		$ 56
Commodity Contract [Member] \| Baltimore Gas and Electric Company [Member] \| External Counterparties \| Collateral [Member]
Derivative [Line Items]
Other		21
Commodity Contract [Member] \| Delmarva Power and Light Company [Member] \| External Counterparties \| Collateral [Member]
Derivative [Line Items]
Other		25
Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Derivative, Notional Amount		567	665
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 567	$ 665

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Mark-to-market derivative assets, current	$ 1,507	$ 644
Derivative Asset, Noncurrent	665	555
Mark-to-market derivative liabilities, current	(1,717)	(295)
Mark-to-market derivative liabilities, noncurrent	(721)	(473)
Margin Deposit Assets	(2,084)	(209)
Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	1,505	639
Derivative Asset, Noncurrent	661	554
Total mark-to-market derivative assets	2,166	1,193
Mark-to-market derivative liabilities, current	(1,710)	(293)
Mark-to-market derivative liabilities, noncurrent	(720)	(472)
Total mark-to-market derivative liabilities	(2,430)	(765)
Total mark-to-market derivative net assets (liabilities)	(264)	428
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	1,505	644
Derivative Asset, Noncurrent	664	555
Mark-to-market derivative liabilities, current	(1,709)	(262)
Mark-to-market derivative liabilities, noncurrent	(511)	(205)
Margin Deposit Assets	(2,084)	(209)
Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	1,505	639
Derivative Asset, Noncurrent	661	554
Total mark-to-market derivative assets	2,166	1,193
Mark-to-market derivative liabilities, current	(1,705)	(260)
Mark-to-market derivative liabilities, noncurrent	(511)	(204)
Total mark-to-market derivative liabilities	(2,216)	(464)
Total mark-to-market derivative net assets (liabilities)	(50)	729
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities, current	(5)	(33)
Mark-to-market derivative liabilities, noncurrent	(209)	(268)
Collateral [Member] \| Commodity Contract [Member] \| External Counterparties
Derivative [Line Items]
Cash Collateral Posted	1
Cash Collateral Held		(15)
Collateral [Member] \| Commodity Contract [Member] \| Affiliates
Derivative [Line Items]
Cash Collateral Posted	71
Collateral [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	(790)	103
Derivative Asset, Noncurrent	(201)	64
Total mark-to-market derivative assets	(991)	167
Mark-to-market derivative liabilities, current	(559)	131
Mark-to-market derivative liabilities, noncurrent	(95)	118
Total mark-to-market derivative liabilities	(654)	249
Total mark-to-market derivative net assets (liabilities)	(1,645)	416
Collateral [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member] \| External Counterparties
Derivative [Line Items]
Cash Collateral Posted	1
Cash Collateral Held		(15)
Collateral [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member] \| Affiliates
Derivative [Line Items]
Cash Collateral Posted	71
Collateral [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member] \| Commonwealth Edison Co [Member]
Derivative [Line Items]
Cash Collateral Posted	50
Netting [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	(17,399)	(2,261)
Derivative Asset, Noncurrent	(2,755)	(1,015)
Total mark-to-market derivative assets	(20,154)	(3,276)
Mark-to-market derivative liabilities, current	17,399	2,261
Mark-to-market derivative liabilities, noncurrent	2,755	1,015
Total mark-to-market derivative liabilities	20,154	3,276
Total mark-to-market derivative net assets (liabilities)	0	0
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	19,631	2,757
Derivative Asset, Noncurrent	3,612	1,501
Total mark-to-market derivative assets	23,243	4,258
Mark-to-market derivative liabilities, current	(18,490)	(2,629)
Mark-to-market derivative liabilities, noncurrent	(3,168)	(1,335)
Total mark-to-market derivative liabilities	(21,658)	(3,964)
Total mark-to-market derivative net assets (liabilities)	1,585	294
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commonwealth Edison Co [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	0	0
Derivative Asset, Noncurrent	0	0
Total mark-to-market derivative assets	0	0
Mark-to-market derivative liabilities, current	(5)	(33)
Mark-to-market derivative liabilities, noncurrent	(209)	(268)
Total mark-to-market derivative liabilities	(214)	(301)
Total mark-to-market derivative net assets (liabilities)	(214)	(301)
Not Designated as Hedging Instrument, Trading [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	63	40
Derivative Asset, Noncurrent	5	4
Total mark-to-market derivative assets	68	44
Mark-to-market derivative liabilities, current	(55)	(23)
Mark-to-market derivative liabilities, noncurrent	(3)	(2)
Total mark-to-market derivative liabilities	(58)	(25)
Total mark-to-market derivative net assets (liabilities)	$ 10	$ 19

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 1,244	$ 448
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			1,244	448
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 755	$ 248	1,248	462
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	755	248	1,248	462
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Operating revenues [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(637)	39	(961)	238
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Operating revenues [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(637)	39	(961)	238
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Purchased power and fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	1,392	209	2,209	224
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Purchased power and fuel [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 1,392	$ 209	$ 2,209	$ 224

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
Derivative [Line Items]
Cash Collateral Held	$ 188
Letters Of Credit Held	117
Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	1,143
Total Exposure Before Credit Collateral [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	110
Total Exposure Before Credit Collateral [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	309
Total Exposure Before Credit Collateral [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	701
Total Exposure Before Credit Collateral [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	23
Credit Collateral [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	305
Credit Collateral [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	1
Credit Collateral [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	48
Credit Collateral [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	254
Credit Collateral [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	2
Net Exposure [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	838
Net Exposure [Member] \| Financial institutions [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	53
Net Exposure [Member] \| Investor-owned utilities, marketers, power producers [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	652
Net Exposure [Member] \| Energy cooperatives and municipalities [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	62
Net Exposure [Member] \| Other [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	71
Net Exposure [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	109
Net Exposure [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	261
Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	447
Net Exposure [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 21
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Number of Counterparties	0
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Number of Counterparties	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 0

Derivative Financial Instrume_7

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	$ (5,289)	$ (834)
Offsetting Fair Value of In-the-Money Contracts Under Master Netting Agreements	2,735	537
Derivative liabilities, fair value	$ (2,554)	$ (297)

Derivative Financial Instrume_8

Derivative Financial Instruments Derivative Financial Instruments - Summary of Cash Collateral and Letters of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 299	$ 511
Derivative, Collateral, Right to Reclaim Securities	477	226
Derivative, Collateral, Obligation to Return Cash	1,872	110
Derivative, Collateral, Obligation to Return Securities	130	40
Incremental Collateral For Loss Of Investment Grade Credit Rating	3,001	1,432
Exelon Generation Co L L C [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	299	511
Derivative, Collateral, Right to Reclaim Securities	477	226
Derivative, Collateral, Obligation to Return Cash	1,872	110
Derivative, Collateral, Obligation to Return Securities	130	40
Incremental Collateral For Loss Of Investment Grade Credit Rating	$ 3,001	$ 1,432

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
ShortTermDebt03232017 \| Corporate [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
ShortTermDebt03242021 \| Corporate [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	200
ShortTermDebt03312021.1 \| Corporate [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	150
ShortTermDebt03312021.2 \| Corporate [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	150
ShortTermDebt03192020 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	200
ShortTermDebt300 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	300
ShortTermDebt08062021 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	880
ShortTermDebt01252021.1 \| Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	125
ShortTermDebt01252021.2 \| Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	125
ExGenBilatJan2013 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
ExGenBilatFeb2019 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
ExGenBilatJan2016 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	150
ExGenBilatOct2012 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net	200
WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	150
Non-Recourse Debt	145
WestMedMarch2026 \| Non-Recourse Debt [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount	$ 113
Derivative, Fixed Interest Rate	0.61%
WestMedMarch2026 \| Exelon Generation Co L L C [Member] \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR + 3
Debt Instrument, Face Amount	$ 150
Non-Recourse Debt	145
WestMedMarch2026 \| Exelon Generation Co L L C [Member] \| Non-Recourse Debt [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount	$ 113
Derivative, Fixed Interest Rate	0.61%
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt03232017 \| Corporate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt03242021 \| Corporate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt03312021.1 \| Corporate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt03312021.2 \| Corporate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt03192020 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.875
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt300 \| Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.70
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt08062021 \| Exelon Generation Co L L C [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.875
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt08062021 \| Exelon Generation Co L L C [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 1
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt01252021.1 \| Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.50
London Interbank Offered Rate (LIBOR) [Member] \| ShortTermDebt01252021.2 \| Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.75
London Interbank Offered Rate (LIBOR) [Member] \| WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 3
London Interbank Offered Rate (LIBOR) [Member] \| WestMedMarch2026 \| Exelon Generation Co L L C [Member] \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 3

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Commercial Paper	$ 287	$ 1,031
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.19%	0.25%
Corporate [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 0
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 340
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.27%
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 323
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.23%
PECO Energy Co [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 0
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	0	0
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 287	$ 368
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.19%	0.24%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 40	$ 35
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.15%	0.22%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 22	$ 146
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.15%	0.24%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 225	$ 187
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.20%	0.25%

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150
Corporate [Member] \| SoftAgree362Dec2025 \| Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest Rate	3.62%
Debt Instrument, Face Amount	$ 4
Exelon Generation Co L L C [Member] \| WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR + 3
Debt Instrument, Face Amount	$ 150
Exelon Generation Co L L C [Member] \| EEPF253April2021 \| Notes Payable, Other Payables[Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
Debt Instrument, Face Amount	$ 1
Exelon Generation Co L L C [Member] \| EEPF4242021 \| Notes Payable, Other Payables[Member]
Debt Instrument [Line Items]
Interest Rate	4.24%
Debt Instrument, Face Amount	$ 1
Commonwealth Edison Co [Member] \| FMB313Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.13%
Debt Instrument, Face Amount	$ 700
Commonwealth Edison Co [Member] \| FMB300March2050 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.75%
Debt Instrument, Face Amount	$ 450
PECO Energy Co [Member] \| FMB305Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.05%
Debt Instrument, Face Amount	$ 375
PECO Energy Co [Member] \| FMB285Sep2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.85%
Debt Instrument, Face Amount	$ 375
Baltimore Gas and Electric Company [Member] \| SN225June2031
Debt Instrument [Line Items]
Interest Rate	2.25%
Debt Instrument, Face Amount	$ 600
Potomac Electric Power Company [Member] \| FMB232Mar2031 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.32%
Debt Instrument, Face Amount	$ 150
Potomac Electric Power Company [Member] \| FMB329Sep2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.29%
Debt Instrument, Face Amount	$ 125
Delmarva Power and Light Company [Member] \| FMB324Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.24%
Debt Instrument, Face Amount	$ 125
Atlantic City Electric Company [Member] \| FMB230Mar2031 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.30%
Debt Instrument, Face Amount	$ 350

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 44	$ 73
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	32	$ 55
Middle Market Lending [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	359
Middle Market Lending [Member] \| Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	359
Private Equity Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	174
Private Equity Funds [Member] \| Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	174
Real Estate Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	371
Real Estate Funds [Member] \| Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 371

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at Amortized Cost (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	$ 390	$ 390
Spent Nuclear Fuel Obligation, Noncurrent	1,209	1,208
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	38,644	36,912
Long-term debt to financing trust	390	390
Spent Nuclear Fuel Obligation, Noncurrent	1,209	1,208
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	43,859	43,752
Long-term debt to financing trust	479	467
Spent Nuclear Fuel Obligation, Noncurrent	1,021	909
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	40,570	40,688
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	1,021	909
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,289	3,064
Long-term debt to financing trust	479	467
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Exelon Generation Co L L C [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Spent Nuclear Fuel Obligation, Noncurrent	1,209	1,208
Exelon Generation Co L L C [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	6,130	6,087
Spent Nuclear Fuel Obligation, Noncurrent	1,209	1,208
Exelon Generation Co L L C [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	6,946	6,856
Spent Nuclear Fuel Obligation, Noncurrent	1,021	909
Exelon Generation Co L L C [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Exelon Generation Co L L C [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	5,835	5,648
Spent Nuclear Fuel Obligation, Noncurrent	1,021	909
Exelon Generation Co L L C [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,111	1,208
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Commonwealth Edison Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	9,772	8,983
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	11,344	11,117
Long-term debt to financing trust	255	246
Commonwealth Edison Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Long-term debt to financing trust	0	0
Commonwealth Edison Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	11,344	11,117
Long-term debt to financing trust	0	0
Commonwealth Edison Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Long-term debt to financing trust	255	246
PECO Energy Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	184	184
PECO Energy Co [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,196	3,753
Long-term debt to financing trust	184	184
PECO Energy Co [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,788	4,603
Long-term debt to financing trust	224	221
PECO Energy Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Long-term debt to financing trust	0	0
PECO Energy Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,738	4,553
Long-term debt to financing trust	0	0
PECO Energy Co [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	50	50
Long-term debt to financing trust	224	221
Baltimore Gas and Electric Company [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,960	3,664
Baltimore Gas and Electric Company [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,416	4,366
Baltimore Gas and Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Baltimore Gas and Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,416	4,366
Baltimore Gas and Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Pepco Holdings LLC [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	7,482	7,006
Pepco Holdings LLC [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	8,158	7,905
Pepco Holdings LLC [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Pepco Holdings LLC [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	6,030	6,099
Pepco Holdings LLC [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	2,128	1,806
Potomac Electric Power Company [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,441	3,165
Potomac Electric Power Company [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	4,216	4,084
Potomac Electric Power Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Potomac Electric Power Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,226	3,336
Potomac Electric Power Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	990	748
Delmarva Power and Light Company [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,808	1,677
Delmarva Power and Light Company [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,992	1,939
Delmarva Power and Light Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Delmarva Power and Light Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,433	1,484
Delmarva Power and Light Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	559	455
Atlantic City Electric Company [Member] \| Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,510	1,413
Atlantic City Electric Company [Member] \| Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,686	1,620
Atlantic City Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Atlantic City Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,107	1,018
Atlantic City Electric Company [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	$ 579	$ 602

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	$ 1,717		$ 1,717	$ 295
Derivative Liability, Noncurrent	721		721	473
Margin Deposit Assets	(2,084)		(2,084)	(209)
Unrealized Gain (Loss) on Investments	(179)		(83)
Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	2,573		2,573	686
DPP consideration	501		501	639
Assets, Fair Value Disclosure	21,421		21,421	17,776
Deferred Compensation Liability, Current and Noncurrent	(149)		(149)	(145)
Total Liabilities	(2,579)		(2,579)	(910)
Fair Value, Net Asset (Liability)	18,842		18,842	16,866
Derivative Asset, Notional Amount	728		728	1,043
Margin Deposit Assets	(2,084)		(2,084)	(209)
Derivative, Notional Amount	194		194	104
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	0		0	2
Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(2,430)		(2,430)	(765)
Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(21,872)		(21,872)	(4,265)
Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(58)		(58)	(25)
Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	19,500		19,500	3,525
Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	689		689	409
Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	222		222	59
Fair Value, Recurring [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	54		54	53
Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	15,732		15,732	14,780
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	130		130	181
Financial Instruments Sold, Not yet Purchased, Corporate Debt	(50)		(50)	(62)
Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	782		782	305
Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,650		7,650	7,525
Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,065		5,065	4,926
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,442		1,442	1,770
Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,221		2,221	1,997
Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	54		54	56
Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	101
Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,319		1,319	1,002
Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	779		779	841
Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	654		654	504
Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	802		802	679
Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	312		312	283
Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	65		65	60
Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	104		104	91
Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	11
Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	133		133	121
Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	137		137	195
Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,166		2,166	1,193
Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	23,243		23,243	4,258
Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	68		68	44
Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21,145)		(21,145)	(3,109)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	2,573		2,573	686
DPP consideration	0		0	0
Assets, Fair Value Disclosure	11,181		11,181	7,137
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	(3)		(3)	(142)
Fair Value, Net Asset (Liability)	11,178		11,178	6,995
Collateral received from counterparties, net of collateral paid to counterparties	(345)		(345)	(67)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(3)		(3)	(142)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(4,126)		(4,126)	(682)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	4,123		4,123	540
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,243		7,243	5,967
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	647		647	210
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,373		4,373	3,886
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,223		2,223	1,871
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,192		2,192	1,871
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	31		31	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	169		169	151
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	65		65	60
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	104		104	91
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	137		137	195
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,059		1,059	138
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	5,527		5,527	745
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(4,468)		(4,468)	(607)
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	501		501	639
Assets, Fair Value Disclosure	4,578		4,578	5,052
Deferred Compensation Liability, Current and Noncurrent	(149)		(149)	(145)
Total Liabilities	(214)		(214)	(176)
Fair Value, Net Asset (Liability)	4,364		4,364	4,876
Collateral received from counterparties, net of collateral paid to counterparties	(710)		(710)	321
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(65)		(65)	(31)
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(9,192)		(9,192)	(1,928)
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(32)		(32)	(21)
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	9,159		9,159	1,918
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,148		3,148	3,981
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	135		135	95
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,717		1,717	2,077
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,296		1,296	1,809
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,155		1,155	1,485
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	126
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	54		54	56
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	101
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	41
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	109		109	98
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	11
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	99		99	87
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	820		820	334
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	10,633		10,633	1,914
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	56		56	17
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(9,869)		(9,869)	(1,597)
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	0		0	0
Assets, Fair Value Disclosure	796		796	1,252
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	(2,362)		(2,362)	(592)
Fair Value, Net Asset (Liability)	(1,566)		(1,566)	660
Collateral received from counterparties, net of collateral paid to counterparties	(590)		(590)	162
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(2,362)		(2,362)	(592)
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(8,554)		(8,554)	(1,655)
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(26)		(26)	(4)
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	6,218		6,218	1,067
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	475		475	497
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1		1	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	287		287	285
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	287		287	285
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	187		187	212
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	287		287	721
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	7,083		7,083	1,599
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	12		12	27
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,808)		(6,808)	(905)
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	0		0	0
Assets, Fair Value Disclosure	4,866		4,866	4,335
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	4,866		4,866	4,335
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,866		4,866	4,335
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,559		1,559	1,562
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,259		1,259	961
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,259		1,259	961
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	592		592	629
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	654		654	504
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	802		802	679
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	2,554		2,554	297
Mark-to-market derivative liabilities (current liabilities)	1,709		1,709	262
Derivative Liability, Noncurrent	511		511	205
Margin Deposit Assets	(2,084)		(2,084)	(209)
Unrealized Gain (Loss) on Investments	(179)		(83)
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,673		1,673	124
DPP consideration	501		501	639
Assets, Fair Value Disclosure	20,281		20,281	16,992
Deferred Compensation Liability, Current and Noncurrent	(44)		(44)	(42)
Total Liabilities	(2,260)		(2,260)	(506)
Fair Value, Net Asset (Liability)	18,021		18,021	16,486
Derivative Asset, Notional Amount	728		728	1,043
Margin Deposit Assets	(2,084)		(2,084)	(209)
Derivative, Notional Amount	194		194	104
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	0		0	2
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Investments in Equity
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments		$ 220
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(2,216)		(2,216)	(464)
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(21,658)		(21,658)	(3,964)
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(58)		(58)	(25)
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	19,500		19,500	3,525
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	292		292	171
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	54		54	20
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	15,732		15,732	14,780
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	130		130	181
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	782		782	305
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,650		7,650	7,525
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,065		5,065	4,926
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,442		1,442	1,770
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,221		2,221	1,997
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	54		54	56
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	101
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,319		1,319	1,002
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	779		779	841
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	654		654	504
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	802		802	679
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	72		72	61
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4		4	4
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	35		35	29
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	33		33	28
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	137		137	195
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,166		2,166	1,193
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	23,243		23,243	4,258
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	68		68	44
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21,145)		(21,145)	(3,109)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,673		1,673	124
DPP consideration	0		0	0
Assets, Fair Value Disclosure	10,151		10,151	6,457
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	(3)		(3)	(142)
Fair Value, Net Asset (Liability)	10,148		10,148	6,315
Collateral received from counterparties, net of collateral paid to counterparties	(345)		(345)	(67)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(3)		(3)	(142)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(4,126)		(4,126)	(682)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	4,123		4,123	540
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,243		7,243	5,967
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	647		647	210
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,373		4,373	3,886
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,223		2,223	1,871
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,192		2,192	1,871
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	31		31	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	39		39	33
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4		4	4
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	35		35	29
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	137		137	195
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,059		1,059	138
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	5,527		5,527	745
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(4,468)		(4,468)	(607)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	501		501	639
Assets, Fair Value Disclosure	4,502		4,502	4,982
Deferred Compensation Liability, Current and Noncurrent	(44)		(44)	(42)
Total Liabilities	(109)		(109)	(73)
Fair Value, Net Asset (Liability)	4,393		4,393	4,909
Collateral received from counterparties, net of collateral paid to counterparties	(710)		(710)	321
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(65)		(65)	(31)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(9,192)		(9,192)	(1,928)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(32)		(32)	(21)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	9,159		9,159	1,918
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,148		3,148	3,981
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	135		135	95
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,717		1,717	2,077
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,296		1,296	1,809
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,155		1,155	1,485
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	126
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	54		54	56
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	101
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	29		29	41
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	33		33	28
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	33		33	28
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	820		820	334
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	10,633		10,633	1,914
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	56		56	17
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(9,869)		(9,869)	(1,597)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	0		0	0
Assets, Fair Value Disclosure	762		762	1,218
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	(2,148)		(2,148)	(291)
Fair Value, Net Asset (Liability)	(1,386)		(1,386)	927
Collateral received from counterparties, net of collateral paid to counterparties	(590)		(590)	162
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(2,148)		(2,148)	(291)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(8,340)		(8,340)	(1,354)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(26)		(26)	(4)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	6,218		6,218	1,067
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	475		475	497
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1		1	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	287		287	285
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	287		287	285
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	187		187	212
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	287		287	721
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	7,083		7,083	1,599
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	12		12	27
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,808)		(6,808)	(905)
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
DPP consideration	0		0	0
Assets, Fair Value Disclosure	4,866		4,866	4,335
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	4,866		4,866	4,335
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,866		4,866	4,335
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,559		1,559	1,562
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,259		1,259	961
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,259		1,259	961
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	592		592	629
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	654		654	504
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	802		802	679
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Commodity derivative assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedges [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0		0	0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	5		5	33
Derivative Liability, Noncurrent	209		209	268
Unrealized Gain (Loss) on Investments	0		0
Commonwealth Edison Co [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents				43
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	309		309	285
Assets, Fair Value Disclosure	309		309	285
Total mark-to-market derivative liabilities	(214)		(214)	(301)
Deferred Compensation Liability, Current and Noncurrent	(9)		(9)	(8)
Total Liabilities	(223)		(223)	(309)
Fair Value, Net Asset (Liability)	86		86	(24)
Mark-to-market derivative liabilities (current liabilities)	5		5	33
Derivative Liability, Noncurrent	209		209	268
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	145		145	83
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	107		107	37
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	44		44	44
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	309		309	285
Assets, Fair Value Disclosure	309		309	285
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	309		309	285
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	(9)		(9)	(8)
Total Liabilities	(9)		(9)	(8)
Fair Value, Net Asset (Liability)	(9)		(9)	(8)
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Total mark-to-market derivative liabilities	(214)		(214)	(301)
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	(214)		(214)	(301)
Fair Value, Net Asset (Liability)	(214)		(214)	(301)
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
PECO Energy Co [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	247		247	8
Assets, Fair Value Disclosure	272		272	30
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	(8)		(8)	(9)
Total Liabilities	(8)		(8)	(9)
Fair Value, Net Asset (Liability)	264		264	21
PECO Energy Co [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	105		105	18
PECO Energy Co [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	25		25	22
PECO Energy Co [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	9
PECO Energy Co [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	15		15	13
PECO Energy Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	247		247	8
Assets, Fair Value Disclosure	257		257	17
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	257		257	17
PECO Energy Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	9
PECO Energy Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	9
PECO Energy Co [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
PECO Energy Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	15		15	13
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	(8)		(8)	(9)
Total Liabilities	(8)		(8)	(9)
Fair Value, Net Asset (Liability)	7		7	4
PECO Energy Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	15		15	13
PECO Energy Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
PECO Energy Co [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	15		15	13
PECO Energy Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
PECO Energy Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
PECO Energy Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
PECO Energy Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	169		169	120
Assets, Fair Value Disclosure	183		183	130
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	(6)		(6)	(5)
Total Liabilities	(6)		(6)	(5)
Fair Value, Net Asset (Liability)	177		177	125
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	56		56	24
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	27		27	1
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	10
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	10
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	169		169	120
Assets, Fair Value Disclosure	183		183	130
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	183		183	130
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	10
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	10
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	(6)		(6)	(5)
Total Liabilities	(6)		(6)	(5)
Fair Value, Net Asset (Liability)	(6)		(6)	(5)
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Total mark-to-market derivative liabilities	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Baltimore Gas and Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	100		100	86
Assets, Fair Value Disclosure	244		244	226
Deferred Compensation Liability, Current and Noncurrent	(19)		(19)	(17)
Total Liabilities	(19)		(19)	(17)
Fair Value, Net Asset (Liability)	225		225	209
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	57		57	74
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5		5	0
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	9		9	10
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144		144	140
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	59		59	55
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	14
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	11
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	61		61	60
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	100		100	86
Assets, Fair Value Disclosure	173		173	155
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	173		173	155
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	73		73	69
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	59		59	55
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	14		14	14
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	37		37	37
Deferred Compensation Liability, Current and Noncurrent	(19)		(19)	(17)
Total Liabilities	(19)		(19)	(17)
Fair Value, Net Asset (Liability)	18		18	20
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	37		37	37
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10		10	11
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	27		27	26
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	34		34	34
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	34		34	34
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Potomac Electric Power Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	36		36	35
Assets, Fair Value Disclosure	155		155	150
Deferred Compensation Liability, Current and Noncurrent	(2)		(2)	(2)
Total Liabilities	(2)		(2)	(2)
Fair Value, Net Asset (Liability)	153		153	148
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	19		19	30
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5		5	0
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	119		119	115
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	58		58	53
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	2
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	61		61	60
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	36		36	35
Assets, Fair Value Disclosure	94		94	88
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	94		94	88
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	58		58	53
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	58		58	53
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	27		27	28
Deferred Compensation Liability, Current and Noncurrent	(2)		(2)	(2)
Total Liabilities	(2)		(2)	(2)
Fair Value, Net Asset (Liability)	25		25	26
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	27		27	28
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	2
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	27		27	26
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	34		34	34
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	34		34	34
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	34		34	34
Delmarva Power and Light Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	26		26	0
Assets, Fair Value Disclosure	26		26	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	26		26	0
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	13		13	15
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	26		26	0
Assets, Fair Value Disclosure	26		26	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	26		26	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Delmarva Power and Light Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Unrealized Gain (Loss) on Investments	0		0
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	14		14	13
Assets, Fair Value Disclosure	14		14	13
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	14		14	13
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	16		16	17
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	9		9	10
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	14		14	13
Assets, Fair Value Disclosure	14		14	13
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	14		14	13
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0	0
Assets, Fair Value Disclosure	0		0	0
Deferred Compensation Liability, Current and Noncurrent	0		0	0
Total Liabilities	0		0	0
Fair Value, Net Asset (Liability)	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Atlantic City Electric Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0		0	0
Exelon Generation Co LLC Affiliate [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Financial Instruments Sold, Not yet Purchased, Corporate Debt	(50)		(50)	(62)
Maturity Less than 30 Days [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash	109		109	116
Maturity Less than 30 Days [Member] \| Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash	$ 109		$ 109	$ 116

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ (235)	$ 883	$ 660	$ 1,068
Total realized / unrealized gains (losses)
Included in net income	(967)	(327)	(1,600)	(483)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	62	32	105	14
Change in collateral	(413)	(79)	(751)	(120)
Purchases, sales, issuances and settlements
Purchases	8	66	123	136
Sales	6	(3)	7	(27)
Settlements	(2)	0	(50)	(15)
Transfers into Level 3	2		4	(5)
Transfers out of Level 3	(27)	9	(64)	13
Ending Balance	(1,566)	581	(1,566)	581
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,001)	(222)	(1,521)	(107)
Fair Value, Inputs, Level 3 [Member] \| Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	0	0	0	0
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	(11)	(18)	(18)	(17)
Included in regulatory assets	11	18	18	17
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0		0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	0	0	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	34	(105)	(80)	(376)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	(4)	1,158	927	1,328
Total realized / unrealized gains (losses)
Included in net income	(967)	(315)	(1,602)	(473)
Included in noncurrent payables to affiliates	11	18	18	17
Included in regulatory assets	0	0	0	0
Change in collateral	(413)	(79)	(751)	(120)
Purchases, sales, issuances and settlements
Purchases	8	66	123	136
Sales	6	(3)	7	(27)
Settlements	(2)	(3)	(48)	(18)
Transfers into Level 3	2		4	(5)
Transfers out of Level 3	(27)	9	(64)	13
Ending Balance	(1,386)	851	(1,386)	851
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,001)	(210)	(1,523)	(97)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	461	499	497	511
Total realized / unrealized gains (losses)
Included in net income	3	3	4	1
Included in noncurrent payables to affiliates	11	18	18	17
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	2	1	3	6
Sales	0	0	0	0
Settlements	(2)	(3)	(48)	(18)
Transfers into Level 3	0		1	1
Transfers out of Level 3	0	0	0	0
Ending Balance	475	518	475	518
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	3	4	1
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	(465)	659	430	817
Total realized / unrealized gains (losses)
Included in net income	(970)	(318)	(1,606)	(474)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	(413)	(79)	(751)	(120)
Purchases, sales, issuances and settlements
Purchases	6	65	120	130
Sales	6	(3)	7	(27)
Settlements	0	0	0	0
Transfers into Level 3	2		3	(6)
Transfers out of Level 3	(27)	9	(64)	13
Ending Balance	(1,861)	333	(1,861)	333
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,004)	(213)	(1,527)	(98)
Commonwealth Edison Co [Member] \| Derivative [Member] \| Interest Rate Swap [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Realized Investment Gains (Losses)	2	5	15	23
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	(265)	(318)	(301)	(301)
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	51	14	87	(3)
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0		0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	(214)	(304)	(214)	(304)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)	(49)	(9)	(72)	26
Pepco Holdings LLC [Member] \| Fair Value, Inputs, Level 3 [Member] \| 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	34	43	34	41
Total realized / unrealized gains (losses)
Included in net income	0	(12)	2	(10)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	3	(2)	3
Transfers into Level 3	0		0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	34	34	34	34
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	(12)	2	(10)
Potomac Electric Power Company [Member] \| Fair Value, Inputs, Level 3 [Member] \| 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	34	43	34	41
Total realized / unrealized gains (losses)
Included in net income	0	(12)	2	(10)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	3	(2)	3
Transfers into Level 3	0		0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	34	34	34	34
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0	$ (12)	$ 2	$ (10)

Fair Value of Financial Asset_7

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	$ 967	$ 327	$ 1,600	$ 483
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,001)	(222)	(1,521)	(107)
Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1,274)	(305)	(1,944)	(370)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,361)	(216)	(1,969)	(50)
Purchased Power And Fuel [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	304	(13)	338	(104)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	357	3	443	(48)
Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	(12)	2	(10)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	(12)	2	(10)
Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	3	0	4	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	3	4	1
Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	967	315	1,602	473
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,001)	(210)	(1,523)	(97)
Exelon Generation Co L L C [Member] \| Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1,274)	(305)	(1,944)	(370)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1,361)	(216)	(1,969)	(50)
Exelon Generation Co L L C [Member] \| Purchased Power And Fuel [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	304	(13)	338	(104)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	357	3	443	(48)
Exelon Generation Co L L C [Member] \| Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	3	0	4	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	3	4	1
Pepco Holdings LLC [Member] \| Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	(12)	2	(10)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	(12)	2	(10)
Potomac Electric Power Company [Member] \| Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	(12)	2	(10)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0	$ (12)	$ 2	$ (10)

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ (590,000,000)	$ 162,000,000
Fair Value, Inputs, Level 3 [Member] \| Economic Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(1,257,000,000)	245,000,000
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (214,000,000)	$ (301,000,000)
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	9.77	2.25
Forward gas price assets	1.76	1.57
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Forward heat rate	900.00%	800.00%
Fair Value Inputs Renewable Factor	95.00%	91.00%
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	301	163
Forward gas price assets	23	7.88
Derivative Asset (Liability) Net, Measurement Input	0.07	0.08
Forward heat rate	1000.00%	900.00%
Fair Value Inputs Renewable Factor	122.00%	123.00%
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	55	30
Forward gas price assets	4.16	2.59
Derivative Asset (Liability) Net, Measurement Input	0.0477	0.0493
Forward heat rate	913.00%	885.00%
Fair Value Inputs Renewable Factor	100.00%	99.00%
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.35	0.11
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	1.97	2.37
Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.49	0.32
Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (14,000,000)	$ 23,000,000
Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	16	10
Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	156	106
Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	53	27
Exelon Generation Co L L C [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 2,554,000,000	$ 297,000,000
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	(590,000,000)	162,000,000
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Economic Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (1,257,000,000)	$ 245,000,000
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	9.77	2.25
Forward gas price assets	1.76	1.57
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	301	163
Forward gas price assets	23	7.88
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	55	30
Forward gas price assets	4.16	2.59
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.35	0.11
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	1.97	2.37
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Option Model Valuation Technique [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.49	0.32
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (14,000,000)	$ 23,000,000
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	16	10
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	156	106
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Proprietary Trading [Member] \| Discounted Cash Flow [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	53	27
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (214,000,000)	$ (301,000,000)
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Forward heat rate	900.00%	800.00%
Fair Value Inputs Renewable Factor	95.00%	91.00%
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.07	0.08
Forward heat rate	1000.00%	900.00%
Fair Value Inputs Renewable Factor	122.00%	123.00%
Commonwealth Edison Co [Member] \| Fair Value, Inputs, Level 3 [Member] \| Derivative [Member] \| Discounted Cash Flow [Member] \| Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.0477	0.0493
Forward heat rate	913.00%	885.00%
Fair Value Inputs Renewable Factor	100.00%	99.00%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Mar. 23, 2016USD ($)MW	Dec. 31, 2020USD ($)	Sep. 30, 2021USD ($)Open_claimMGPSiteMW	Dec. 31, 2022MW	Dec. 31, 2018MW	Dec. 31, 2017MW	Mar. 31, 2021USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 3,621
Accrual for Environmental Loss Contingencies, Gross		$ 483	474
Liability for Asbestos and Environmental Claims, Gross		89	82
LDC Damages - Accrued Liability
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages			40
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			3,049
Accrual for Environmental Loss Contingencies, Gross		121	119
Liability for Asbestos and Environmental Claims, Gross		89	82
Exelon Generation Co L L C [Member] \| LDC Damages
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages							$ 40
Exelon Generation Co L L C [Member] \| LDC Damages - Accrued Liability
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages			40
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 224
Mgp Site Contingency Monitoring Count \| MGPSite			21
Accrual for Environmental Loss Contingencies, Gross		293	$ 284
Deferred Prosecution Agreement Payments		200
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 181
Mgp Site Contingency Monitoring Count \| MGPSite			6
Accrual for Environmental Loss Contingencies, Gross		23	$ 23
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 5
Mgp Site Contingency Monitoring Count \| MGPSite			4
Accrual for Environmental Loss Contingencies, Gross		2	$ 6
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			54
Accrual for Environmental Loss Contingencies, Gross		44	42
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			24
Accrual for Environmental Loss Contingencies, Gross		42	40
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 18
Mgp Site Contingency Monitoring Count \| MGPSite			1
Accrual for Environmental Loss Contingencies, Gross		$ 1	$ 1
Open Claims [Member] \| Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross			$ 19
Open Asbestos Related Personal Injury Claims \| Open_claim			211
Estimated Future Claims [Member] \| Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross			$ 63
Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			513
Pepco Holdings Inc [Member] \| Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			320
Pepco Holdings Inc [Member] \| Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			120
Pepco Holdings Inc [Member] \| Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			89
West Lake [Member] \| Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross			290
West Lake [Member] \| Exelon Generation Co L L C [Member] \| Groundwater
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross			40
West Lake [Member] \| Exelon Generation Co L L C [Member] \| Radioactive Residues Environmental Remediation
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Component Amount			90
Other Solar Projects [Member] \| Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Business Acquisition, Expected New Generation Mwh \| MW	37
Other Commitment	$ 135		$ 121
Other Non-Financial Commitment \| MW			33
Other Solar Projects [Member] \| Pepco Holdings Inc [Member] \| Generation Solar Business
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Non-Financial Commitment \| MW			30
Other Solar Projects [Member] \| Pepco Holdings Inc [Member] \| Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 121
Wind Assets [Member] \| Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Non-Financial Commitment \| MW	100
Wind Assets [Member] \| Pepco Holdings Inc [Member] \| Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment \| MW	120			40	40	40

Commitments and Contingencies_3

Commitments and Contingencies - Merger Commitment (Details) $ in Millions	Sep. 30, 2021USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,621
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	54
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	24
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	18
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	12
Pepco Holdings Inc [Member]
Other Commitments [Line Items]
Other Commitment	513
Pepco Holdings Inc [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	74
Pepco Holdings Inc [Member] \| Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	320
Pepco Holdings Inc [Member] \| Pepco Holdings LLC [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	62
Pepco Holdings Inc [Member] \| Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	120
Pepco Holdings Inc [Member] \| Potomac Electric Power Company [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	51
Pepco Holdings Inc [Member] \| Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	89
Pepco Holdings Inc [Member] \| Delmarva Power and Light Company [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	7
Pepco Holdings Inc [Member] \| Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	111
Pepco Holdings Inc [Member] \| Atlantic City Electric Company [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	$ 4

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Sep. 30, 2021USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,621
Other Commitment, to be Paid, Remainder of Fiscal Year	671
Other Commitment, to be Paid, Year One	2,429
Other Commitment, to be Paid, Year Two	116
Other Commitment, to be Paid, Year Three	8
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	391
Guarantor Obligations, Maximum Exposure, Undiscounted	75
Letters of Credit
Other Commitments [Line Items]
Other Commitment	2,241
Other Commitment, to be Paid, Remainder of Fiscal Year	268
Other Commitment, to be Paid, Year One	1,860
Other Commitment, to be Paid, Year Two	113
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	971
Other Commitment, to be Paid, Remainder of Fiscal Year	403
Other Commitment, to be Paid, Year One	566
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	31
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	13
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	3,049
Other Commitment, to be Paid, Remainder of Fiscal Year	616
Other Commitment, to be Paid, Year One	2,320
Other Commitment, to be Paid, Year Two	113
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Exelon Generation Co L L C [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	2,223
Other Commitment, to be Paid, Remainder of Fiscal Year	264
Other Commitment, to be Paid, Year One	1,846
Other Commitment, to be Paid, Year Two	113
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Exelon Generation Co L L C [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	826
Other Commitment, to be Paid, Remainder of Fiscal Year	352
Other Commitment, to be Paid, Year One	474
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	224
Other Commitment, to be Paid, Remainder of Fiscal Year	7
Other Commitment, to be Paid, Year One	15
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	200
Commonwealth Edison Co [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	5
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Commonwealth Edison Co [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	5
Other Commitment, to be Paid, Year One	10
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Commonwealth Edison Co [Member] \| Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	181
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	178
PECO Energy Co [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	1
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
PECO Energy Co [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
PECO Energy Co [Member] \| Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	5
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Baltimore Gas and Electric Company [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Baltimore Gas and Electric Company [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	54
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year One	23
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	13
Guarantor Obligations, Maximum Exposure, Undiscounted	75
Pepco Holdings LLC [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	23
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year One	20
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Pepco Holdings LLC [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	31
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	13
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	24
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	15
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five and Beyond	4
Guarantor Obligations, Maximum Exposure, Undiscounted	25
Potomac Electric Power Company [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	14
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	14
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Potomac Electric Power Company [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	10
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five and Beyond	4
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	18
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	4
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five and Beyond	5
Guarantor Obligations, Maximum Exposure, Undiscounted	32
Delmarva Power and Light Company [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	5
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Delmarva Power and Light Company [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	13
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five and Beyond	5
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	12
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year One	4
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five and Beyond	4
Guarantor Obligations, Maximum Exposure, Undiscounted	18
Atlantic City Electric Company [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	0
Atlantic City Electric Company [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	8
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five and Beyond	$ 4
Minimum [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Maximum [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	$ 474	$ 483
Exelon Generation Co L L C [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	119	121
Commonwealth Edison Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	284	293
PECO Energy Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	23	23
Baltimore Gas and Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	6	2
Pepco Holdings LLC [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	42	44
Potomac Electric Power Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	40	42
Delmarva Power and Light Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	1	1
Atlantic City Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	1	1
Manufactured Gas Plants [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	310	314
Manufactured Gas Plants [Member] \| Exelon Generation Co L L C [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Manufactured Gas Plants [Member] \| Commonwealth Edison Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	284	293
Manufactured Gas Plants [Member] \| PECO Energy Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	21	21
Manufactured Gas Plants [Member] \| Baltimore Gas and Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	5	0
Manufactured Gas Plants [Member] \| Pepco Holdings LLC [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Manufactured Gas Plants [Member] \| Potomac Electric Power Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Manufactured Gas Plants [Member] \| Delmarva Power and Light Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Manufactured Gas Plants [Member] \| Atlantic City Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	$ 0	$ 0

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 34,500	$ 34,313	$ 34,868	$ 34,871	$ 34,616	$ 34,573	$ 34,868	$ 34,573
Other comprehensive income	66	57	54	28	41	21	177	90
Ending balance	34,259	34,500	34,313	35,103	34,871	34,616	34,259	35,103
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(5)		(5)	(3)		(2)	(5)	(2)
OCI before reclassifications	0			(1)			(1)	(2)
Amounts reclassified from AOCI	0			0			0	0
Other comprehensive income	0			(1)			(1)	(2)
Ending balance	(6)	(5)		(4)	(3)		(6)	(4)
Gains (Losses) on Cash Flow Hedges \| Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Ending balance	(5)						(5)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,264)		(3,372)	(3,096)		(3,165)	(3,372)	(3,165)
OCI before reclassifications	14			(13)			15	(17)
Amounts reclassified from AOCI	55			39			163	112
Other comprehensive income	69			26			178	95
Ending balance	(3,194)	(3,264)		(3,070)	(3,096)		(3,194)	(3,070)
Pension and Non-Pension Postretirement Benefit Plan Items \| Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Ending balance	(3,195)						(3,195)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(20)		(23)	(33)		(27)	(23)	(27)
OCI before reclassifications	(3)			3			0	(3)
Amounts reclassified from AOCI	0			0			0	0
Other comprehensive income	(3)			3			0	(3)
Ending balance	(23)	(20)		(30)	(33)		(23)	(30)
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,289)	(3,346)	(3,400)	(3,132)	(3,173)	(3,194)	(3,400)	(3,194)
OCI before reclassifications	11			(11)			14	(22)
Amounts reclassified from AOCI	55			39			163	112
Other comprehensive income	66	57	54	28	41	21	177	90
Ending balance	$ (3,223)	$ (3,289)	$ (3,346)	$ (3,104)	$ (3,132)	$ (3,173)	$ (3,223)	$ (3,104)

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Income - Income Taxes Allocated to Other Comprehensive Income (Loss) Components (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 1	$ 4	$ 3	$ 12
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(19)	(16)	(57)	(50)
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (7)	$ 3	$ (8)	$ 6

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Aug. 06, 2021	Dec. 31, 2020	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 75
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	90.00%		90.00%
VIE Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	90.00%		90.00%
CENG [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%	49.99%
CENG [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	50.01%	50.01%	50.01%
CENG [Member] \| Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 245
CENG [Member] \| Financial Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 165
EGRP [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	51.00%		51.00%
Antelope Valley [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%		100.00%
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	31.00%		31.00%
NER [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%		100.00%
Exelon Generation Co L L C [Member] \| Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	90.00%		90.00%
Exelon Generation Co L L C [Member] \| VIE Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	90.00%		90.00%
Exelon Generation Co L L C [Member] \| CENG [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%	49.99%
Exelon Generation Co L L C [Member] \| CENG [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	50.01%	50.01%	50.01%
Guarantor Obligations, Current Carrying Value	$ 688
Exelon Generation Co L L C [Member] \| EGRP [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	51.00%		51.00%
Exelon Generation Co L L C [Member] \| EGRP [Member] \| Solar project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%
Exelon Generation Co L L C [Member] \| EGRP [Member] \| Wind project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%
Exelon Generation Co L L C [Member] \| Antelope Valley [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%		100.00%
Exelon Generation Co L L C [Member] \| Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	31.00%		31.00%
Exelon Generation Co L L C [Member] \| NER [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%		100.00%

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of Consolidated VIES (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 2,957	$ 663	$ 1,858	$ 587
Restricted cash and cash equivalents		473	438	485	358
Accounts receivable, net
Customer		3,121	3,231
Unamortized energy contract assets		36	38
Inventory, net
Materials and supplies		1,475	1,425
Assets held for sale		11	958
Other current assets		1,665	1,609
Total current assets		14,877	12,562
Property, plant and equipment, net		82,852	82,584
NDT funds		15,404	14,464
Unamortized energy contract assets		265	294
Other Assets, Noncurrent		2,818	2,982
Assets	[1]	132,621	129,317
Long-term debt due within one year		3,375	1,819
Accounts payable		3,694	3,562
Accrued expenses		1,949	2,078
Unamortized energy contract liabilities		92	100
Liabilities held for sale		3	375
Other		1,180	1,264
Total current liabilities		15,826	12,771
Long-term debt		35,269	35,093
Asset retirement obligations, noncurrent		12,907	12,300
Unamortized energy contract liabilities		169	238
Other		2,850	2,942
Total liabilities	[1]	98,362	94,449
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		38	98
Restricted cash and cash equivalents		47	47
Accounts receivable, net
Customer		25	148
Other		7	36
Unamortized energy contract assets		21	22
Inventory, net
Materials and supplies		14	244
Assets held for sale		0	101
Other current assets		517	674
Total current assets		669	1,370
Property, plant and equipment, net		2,052	5,803
NDT funds		0	3,007
Unamortized energy contract assets		210	249
Other Assets, Noncurrent		22	52
Assets, Noncurrent		2,284	9,111
Assets		2,953	10,481
Long-term debt due within one year		80	94
Accounts payable		11	81
Accrued expenses		14	70
Unamortized energy contract liabilities		0	4
Liabilities held for sale		0	16
Other		0	5
Total current liabilities		105	270
Long-term debt		832	889
Asset retirement obligations, noncurrent		149	2,318
Other		3	129
Liabilities, Noncurrent		984	3,336
Total liabilities		1,089	3,606
Unrestricted Assets [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Accounts receivable, net
Unamortized energy contract assets		21	22
Inventory, net
Assets held for sale		0	9
Unamortized energy contract assets		210	249
Other Assets		0	1
Recourse [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Total liabilities		1	8
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		1,957	226	623	303
Restricted cash and cash equivalents		62	89	100	146
Accounts receivable, net
Customer		1,328	1,298
Unamortized energy contract assets		36	38
Inventory, net
Materials and supplies		998	978
Assets held for sale		11	958
Other current assets		1,319	1,357
Total current assets		8,587	6,947
Property, plant and equipment, net		19,574	22,214
NDT funds		15,404	14,464
Unamortized energy contract assets		265	293
Other Assets, Noncurrent		1,589	1,826
Assets	[2]	48,010	48,094
Long-term debt due within one year		1,216	197
Accounts payable		1,612	1,253
Accrued expenses		691	788
Unamortized energy contract liabilities		2	7
Liabilities held for sale		3	375
Other		347	444
Total current liabilities		7,796	5,219
Long-term debt		4,593	5,566
Asset retirement obligations, noncurrent		12,635	12,054
Unamortized energy contract liabilities		1	3
Other		1,224	1,308
Total liabilities	[2]	35,975	33,418
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		38	98
Restricted cash and cash equivalents		42	44
Accounts receivable, net
Customer		25	148
Other		7	36
Unamortized energy contract assets		21	22
Inventory, net
Materials and supplies		14	244
Assets held for sale		0	101
Other current assets		513	669
Total current assets		660	1,362
Property, plant and equipment, net		2,052	5,803
NDT funds		0	3,007
Unamortized energy contract assets		210	249
Other Assets, Noncurrent		13	42
Assets, Noncurrent		2,275	9,101
Assets		2,935	10,463
Long-term debt due within one year		70	68
Accounts payable		11	81
Accrued expenses		14	70
Unamortized energy contract liabilities		0	4
Liabilities held for sale		0	16
Other		0	5
Total current liabilities		95	244
Long-term debt		832	889
Asset retirement obligations, noncurrent		149	2,318
Other		3	129
Liabilities, Noncurrent		984	3,336
Total liabilities		1,079	3,580
Exelon Generation Co L L C [Member] \| Unrestricted Assets [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Accounts receivable, net
Unamortized energy contract assets		21	22
Inventory, net
Assets held for sale		0	9
Unamortized energy contract assets		210	249
Other Assets		0	1
Exelon Generation Co L L C [Member] \| Recourse [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Total liabilities		1	8
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		82	111	196	131
Restricted cash and cash equivalents		71	39	38	36
Accounts receivable, net
Customer		566	525
Inventory, net
Materials and supplies		207	198
Other current assets		57	45
Total current assets		1,690	1,599
Property, plant and equipment, net		16,163	15,377
Other Assets, Noncurrent		283	307
Assets	[3]	24,502	23,736
Long-term debt due within one year		405	347
Accounts payable		479	539
Accrued expenses		300	299
Unamortized energy contract liabilities		90	92
Other		154	141
Total current liabilities		2,015	2,154
Long-term debt		7,077	6,659
Asset retirement obligations, noncurrent		69	59
Unamortized energy contract liabilities		168	235
Other		589	622
Total liabilities	[3]	13,861	13,692
Pepco Holdings LLC [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		5	3
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract assets		0	0
Inventory, net
Materials and supplies		0	0
Assets held for sale		0	0
Other current assets		4	5
Total current assets		9	8
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract assets		0	0
Other Assets, Noncurrent		9	10
Assets, Noncurrent		9	10
Assets		18	18
Long-term debt due within one year		10	26
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities		0	0
Liabilities held for sale		0	0
Other		0	0
Total current liabilities		10	26
Long-term debt		0	0
Asset retirement obligations, noncurrent		0	0
Other		0	0
Liabilities, Noncurrent		0	0
Total liabilities		10	26
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		16	17	13	12
Restricted cash and cash equivalents		5	3	$ 4	$ 2
Accounts receivable, net
Customer		184	124
Inventory, net
Other current assets		5	3
Total current assets		376	326
Property, plant and equipment, net		3,649	3,475
Other Assets, Noncurrent		48	50
Assets	[4]	4,532	4,286
Long-term debt due within one year		8	261
Accounts payable		146	177
Accrued expenses		43	46
Other		15	11
Total current liabilities		528	780
Long-term debt		1,502	1,152
Other		52	48
Total liabilities	[4]	2,977	2,895
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		5	3
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract assets		0	0
Inventory, net
Materials and supplies		0	0
Assets held for sale		0	0
Other current assets		0	0
Total current assets		5	3
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract assets		0	0
Other Assets, Noncurrent		9	10
Assets, Noncurrent		9	10
Assets		14	13
Long-term debt due within one year		6	21
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities		0	0
Liabilities held for sale		0	0
Other		0	0
Total current liabilities		6	21
Long-term debt		0	0
Asset retirement obligations, noncurrent		0	0
Other		0	0
Liabilities, Noncurrent		0	0
Total liabilities		$ 6	$ 21

[1]	Exelon’s consolidated assets include $2,722 million and $10,200 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $1,088 million and $3,598 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 17 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $2,704 million and $10,182 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $1,078 million and $3,572 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 17 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both September 30, 2021 and December 31, 2020 of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $10 million and $26 million at September 30, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 17 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $14 million and $13 million at September 30, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $6 million and $21 million at September 30, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 17 — Variable Interest Entities for additional information.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Total assets	[1]	$ 132,621	$ 129,317
Total liabilities	[1]	98,362	94,449
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,151	1,178
Total liabilities		289	284
Exelon's ownership interest in VIE		143	157
Other ownership interests in VIE		719	737
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	[2]	48,010	48,094
Total liabilities	[2]	35,975	33,418
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,151	1,178
Total liabilities		289	284
Exelon's ownership interest in VIE		143	157
Other ownership interests in VIE		719	737
Commercial Agreement VIE [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		781	777
Total liabilities		80	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		701	716
Commercial Agreement VIE [Member] \| Exelon Generation Co L L C [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		781	777
Total liabilities		80	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		701	716
Equity Investment VIE [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		370	401
Total liabilities		209	223
Exelon's ownership interest in VIE		143	157
Other ownership interests in VIE		18	21
Equity Investment VIE [Member] \| Exelon Generation Co L L C [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		370	401
Total liabilities		209	223
Exelon's ownership interest in VIE		143	157
Other ownership interests in VIE		$ 18	$ 21

[1]	Exelon’s consolidated assets include $2,722 million and $10,200 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $1,088 million and $3,598 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 17 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $2,704 million and $10,182 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $1,078 million and $3,572 million at September 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 17 — Variable Interest Entities for additional information.

Supplemental Financial Inform_3

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Supplemental Statement of Operations Information [Line Items]
Operating lease income	$ 30	$ 30	$ 47	$ 48
Variable lease income	71	76	208	225
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	263	50	698	127
Net realized income on NDT funds - Non-regulatory agreement units	102	23	392	127
Net unrealized gains on NDT funds - Regulatory agreement units	(195)	398	84	111
Net unrealized gains on NDT funds - Non-regulatory agreement units	(88)	254	38	1
Regulatory offset to NDT fund-related activities	(38)	(359)	(607)	(192)
Decommissioning-related activities	44	366	605	174
AFUDC - Equity	36	27	99	76
Non-service net periodic benefit cost	19	15	64	38
Unrealized Gain (Loss) on Investments	(179)		(83)
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	29	28	44	43
Variable lease income	71	76	207	224
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	263	50	698	127
Net realized income on NDT funds - Non-regulatory agreement units	102	23	392	127
Net unrealized gains on NDT funds - Regulatory agreement units	(195)	398	84	111
Net unrealized gains on NDT funds - Non-regulatory agreement units	(88)	254	38	1
Regulatory offset to NDT fund-related activities	(38)	(359)	(607)	(192)
Decommissioning-related activities	44	366	605	174
AFUDC - Equity	0	0	0	0
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	(179)		(83)
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	10	7	23	22
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	7	5	19	12
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	7	6	21	16
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	1	1	3	3
Variable lease income	0	0	1	1
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	12	9	36	26
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	9	7	30	20
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	1	1	3	3
Variable lease income	0	0	1	1
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	2	1	4	3
Non-service net periodic benefit cost	0	0	0	0
Unrealized Gain (Loss) on Investments	0		0
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0	0	0
Regulatory offset to NDT fund-related activities	0	0	0	0
Decommissioning-related activities	0	0	0	0
AFUDC - Equity	1	1	2	3
Non-service net periodic benefit cost	0	$ 0	0	$ 0
Unrealized Gain (Loss) on Investments	$ 0		$ 0

Supplemental Financial Inform_4

Supplemental Financial Information - Taxes Other Than Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Supplemental Statement of Operations Information [Line Items]
Utility taxes	$ 242	$ 237	$ 665	$ 651
Property	165	152	470	449
Payroll	57	59	180	183
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	27	26	73	75
Property	66	66	199	199
Payroll	26	29	83	88
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	67	66	188	181
Property	13	7	30	23
Payroll	7	7	20	21
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	41	41	107	102
Property	5	4	13	12
Payroll	4	4	12	12
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	21	21	66	65
Property	46	42	131	121
Payroll	5	4	14	13
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	86	83	231	228
Property	34	32	97	94
Payroll	7	6	21	21
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	80	77	212	210
Property	23	21	65	63
Payroll	2	2	5	6
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	6	5	17	16
Property	10	10	30	29
Payroll	1	1	4	4
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	0	1	2	2
Property	1	1	2	2
Payroll	$ 1	$ 1	$ 2	$ 3

Supplemental Financial Inform_5

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			$ 4,505	$ 2,831
Amortization of regulatory assets			439	434
Amortization of intangible assets, net			44	47
Amortization of energy contract assets and liabilities			23	24
Nuclear fuel			810	708
ARO accretion			383	375
Total depreciation, amortization and accretion			6,204	4,419
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			304	310
Allowance for credit losses			155	130
Other decommissioning-related activity			(810)	(301)
Energy-related options			45	79
True-up adjustments to decoupling mechanisms and formula rates	$ (47)	$ (11)	129	(66)
Restructuring Costs			(67)	96
Inventory Write-down				119
Long-term incentive plan			94	(8)
Amortization of operating ROU asset			146	185
Deferred payments for legal settlements				200
AFUDC - Equity	(36)	(27)	(99)	(76)
Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(129)	66
Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(99)	(76)
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			2,698	1,121
Amortization of regulatory assets			0	0
Amortization of intangible assets, net			37	40
Amortization of energy contract assets and liabilities			23	22
Nuclear fuel			810	708
ARO accretion			383	375
Total depreciation, amortization and accretion			3,951	2,266
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			92	89
Allowance for credit losses			59	16
Other decommissioning-related activity			(810)	(301)
Energy-related options			45	79
Restructuring Costs			(75)	88
Inventory Write-down				118
Long-term incentive plan			0	0
Amortization of operating ROU asset			98	135
Deferred payments for legal settlements				0
AFUDC - Equity	0	0	0	0
Exelon Generation Co L L C [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			0	0
Exelon Generation Co L L C [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			0	0
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			721	689
Amortization of regulatory assets			172	152
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			893	841
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			97	85
Allowance for credit losses			34	23
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	(32)	(38)	32	(51)
Restructuring Costs			1	1
Inventory Write-down				1
Long-term incentive plan			0	0
Amortization of operating ROU asset			2	1
Deferred payments for legal settlements				200
AFUDC - Equity	(10)	(7)	(23)	(22)
Commonwealth Edison Co [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(32)	51
Commonwealth Edison Co [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(23)	(22)
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			249	238
Amortization of regulatory assets			10	21
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			259	259
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			5	4
Allowance for credit losses			36	38
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	3	5	20	10
Restructuring Costs			0	0
Inventory Write-down				1
Long-term incentive plan			0	0
Amortization of operating ROU asset			0	0
Deferred payments for legal settlements				0
AFUDC - Equity	(7)	(5)	(19)	(12)
PECO Energy Co [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(20)	(10)
PECO Energy Co [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(19)	(12)
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			324	293
Amortization of regulatory assets			110	112
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			434	405
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			45	46
Allowance for credit losses			7	12
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	(24)	(9)	(17)	(10)
Restructuring Costs			0	0
Inventory Write-down				0
Long-term incentive plan			0	0
Amortization of operating ROU asset			22	23
Deferred payments for legal settlements				0
AFUDC - Equity	(7)	(6)	(21)	(16)
Baltimore Gas and Electric Company [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			17	10
Baltimore Gas and Electric Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(21)	(16)
Pepco Holdings LLC [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			467	436
Amortization of regulatory assets			147	149
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			614	585
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			36	52
Allowance for credit losses			18	41
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	6	31	94	(15)
Restructuring Costs			1	0
Inventory Write-down				(1)
Long-term incentive plan			0	0
Amortization of operating ROU asset			21	21
Deferred payments for legal settlements				0
AFUDC - Equity	(12)	(9)	(36)	(26)
Pepco Holdings LLC [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(94)	15
Pepco Holdings LLC [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(36)	(26)
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			204	191
Amortization of regulatory assets			98	91
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			302	282
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			5	11
Allowance for credit losses			9	24
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	9	18	54	20
Restructuring Costs			0	0
Inventory Write-down				0
Long-term incentive plan			0	0
Amortization of operating ROU asset			5	5
Deferred payments for legal settlements				0
AFUDC - Equity	(9)	(7)	(30)	(20)
Potomac Electric Power Company [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(54)	(20)
Potomac Electric Power Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(30)	(20)
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			126	116
Amortization of regulatory assets			31	27
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			157	143
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			2	6
Allowance for credit losses			3	15
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	(2)	8	17	(15)
Restructuring Costs			0	0
Inventory Write-down				(1)
Long-term incentive plan			0	0
Amortization of operating ROU asset			7	6
Deferred payments for legal settlements				0
AFUDC - Equity	(2)	(1)	(4)	(3)
Delmarva Power and Light Company [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(17)	15
Delmarva Power and Light Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			(4)	(3)
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			115	104
Amortization of regulatory assets			18	30
Amortization of intangible assets, net			0	0
Amortization of energy contract assets and liabilities			0	0
Nuclear fuel			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			133	134
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			8	10
Allowance for credit losses			6	2
Other decommissioning-related activity			0	0
Energy-related options			0	0
True-up adjustments to decoupling mechanisms and formula rates	0	5	23	(20)
Restructuring Costs			0	0
Inventory Write-down				0
Long-term incentive plan			0	0
Amortization of operating ROU asset			3	2
Deferred payments for legal settlements				0
AFUDC - Equity	$ (1)	$ (1)	(2)	(3)
Atlantic City Electric Company [Member] \| Other Non-Cash Activity
Other Non-Cash Operating Activities [Abstract]
True-up adjustments to decoupling mechanisms and formula rates			(23)	20
Atlantic City Electric Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity			$ (2)	$ (3)

Supplemental Financial Inform_6

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 2,957	$ 663	$ 1,858	$ 587
Restricted cash	473	438	485	358
Restricted cash included in other long-term assets	54	53	137	177
Cash, restricted cash, and cash equivalents - Held for Sale		12
Total cash, restricted cash, and cash equivalents	3,484	1,166	2,480	1,122
Accrued Expenses [Abstract]
Compensation-related accruals	894	1,069
Taxes accrued	508	527
Interest accrued	415	331
Exelon Generation Co L L C [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	1,957	226	623	303
Restricted cash	62	89	100	146
Restricted cash included in other long-term assets	0	0	0	0
Cash, restricted cash, and cash equivalents - Held for Sale		12
Total cash, restricted cash, and cash equivalents	2,019	327	723	449
Accrued Expenses [Abstract]
Compensation-related accruals	318	426
Taxes accrued	222	229
Interest accrued	77	44
Commonwealth Edison Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	241	83	76	90
Restricted cash	276	279	305	150
Restricted cash included in other long-term assets	44	43	127	163
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	561	405	508	403
Accrued Expenses [Abstract]
Compensation-related accruals	148	170
Taxes accrued	80	94
Interest accrued	65	109
PECO Energy Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	344	19	242	21
Restricted cash	8	7	7	6
Restricted cash included in other long-term assets	0	0	0	0
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	352	26	249	27
Accrued Expenses [Abstract]
Compensation-related accruals	66	73
Taxes accrued	61	16
Interest accrued	36	37
Baltimore Gas and Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	225	144	326	24
Restricted cash	27	1	1	1
Restricted cash included in other long-term assets	0	0	0	0
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	252	145	327	25
Accrued Expenses [Abstract]
Compensation-related accruals	72	84
Taxes accrued	90	73
Interest accrued	39	46
Pepco Holdings LLC [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	82	111	196	131
Restricted cash	71	39	38	36
Restricted cash included in other long-term assets	9	10	10	14
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	162	160	244	181
Accrued Expenses [Abstract]
Compensation-related accruals	108	109
Taxes accrued	98	117
Interest accrued	75	51
Potomac Electric Power Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	19	30	125	30
Restricted cash	41	35	33	33
Restricted cash included in other long-term assets	0	0	0	0
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	60	65	158	63
Accrued Expenses [Abstract]
Compensation-related accruals	34	36
Taxes accrued	67	90
Interest accrued	37	26
Delmarva Power and Light Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	13	15	26	13
Restricted cash	26	0	0	0
Restricted cash included in other long-term assets	0	0	0	0
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	39	15	26	13
Accrued Expenses [Abstract]
Compensation-related accruals	21	18
Taxes accrued	16	18
Interest accrued	20	7
Atlantic City Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	16	17	13	12
Restricted cash	5	3	4	2
Restricted cash included in other long-term assets	9	10	10	14
Cash, restricted cash, and cash equivalents - Held for Sale		0
Total cash, restricted cash, and cash equivalents	30	30	$ 27	$ 28
Accrued Expenses [Abstract]
Compensation-related accruals	16	17
Taxes accrued	7	12
Interest accrued	$ 15	$ 12

Related Party Transactions - Op

Related Party Transactions - Operating Revenues and Purchased Power and Fuel (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Related Party Transaction [Line Items]
Revenue from Related Parties	$ 0	$ 1	$ 0	$ 4
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	324	331	872	932
Exelon Generation Co L L C [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	96	71	249	241
Purchased power and/or fuel from affiliates	2	0	7	11
Exelon Generation Co L L C [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	59	68	142	146
Exelon Generation Co L L C [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	65	84	195	252
Exelon Generation Co L L C [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	99	105	276	288
Exelon Generation Co L L C [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	69	80	199	219
Exelon Generation Co L L C [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	25	21	63	60
Exelon Generation Co L L C [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	5	4	14	9
Exelon Generation Co L L C [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	5	3	10	5
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	9	15	19	31
Purchased power and/or fuel from affiliates	93	71	256	252
Commonwealth Edison Co [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Purchased power and/or fuel from affiliates	$ 94	$ 71	$ 256	$ 252

Related Party Transactions - BS

Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	$ 149	$ 148	$ 431	$ 390
PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	18	15	54	45
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	177	132	458	409
Exelon Generation Co L L C [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	145	133	424	406
Related Party Transaction Capitalized Costs Support Services	43	13	76	37
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	73	69	217	209
Commonwealth Edison Co [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	71	65	214	204
Related Party Transaction Capitalized Costs Support Services	47	49	148	133
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	43	37	126	114
PECO Energy Co [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	41	34	120	107
Related Party Transaction Capitalized Costs Support Services	12	20	57	53
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	46	39	137	122
Baltimore Gas and Electric Company [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	45	38	133	120
Related Party Transaction Capitalized Costs Support Services	20	30	62	88
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	43	38	122	111
Pepco Holdings LLC [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	40	36	116	107
Related Party Transaction Capitalized Costs Support Services	27	36	88	79
Pepco Holdings LLC [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0	0	0	0
Related Party Transaction Capitalized Costs Support Services	18	15	54	45
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	52	49	155	152
Potomac Electric Power Company [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	23	20	68	61
Related Party Transaction Capitalized Costs Support Services	11	14	36	29
Potomac Electric Power Company [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	26	28	84	90
Related Party Transaction Capitalized Costs Support Services	7	7	22	20
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	40	37	117	112
Delmarva Power and Light Company [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	14	13	43	38
Related Party Transaction Capitalized Costs Support Services	10	12	29	26
Delmarva Power and Light Company [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	24	24	73	73
Related Party Transaction Capitalized Costs Support Services	6	4	17	13
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	35	32	103	98
Atlantic City Electric Company [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	14	11	37	32
Related Party Transaction Capitalized Costs Support Services	7	10	22	22
Atlantic City Electric Company [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	21	21	64	65
Related Party Transaction Capitalized Costs Support Services	$ 5	$ 4	$ 15	$ 12

Related Party Transactions - Cu

Related Party Transactions - Current Receivables From/Payables To Affiliates (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 549	$ 544
Accounts Payable, Related Parties, Current	5	5
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	154	107
Accounts Receivable, Related Parties, Current	184	153
Exelon Generation Co L L C [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	103	78
Due to Related Parties, Current	27	50
Exelon Generation Co L L C [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	24	17
Exelon Generation Co L L C [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	15	11
Exelon Generation Co L L C [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Exelon Generation Co L L C [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	22	13
Exelon Generation Co L L C [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	4	3
Exelon Generation Co L L C [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	6
Exelon Generation Co L L C [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	25
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	131	96
Accounts Receivable, Related Parties, Current	41	22
Commonwealth Edison Co [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	36	13
Accounts Payable, Related Parties, Current	76	28
Commonwealth Edison Co [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	158	146
Commonwealth Edison Co [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	1
Commonwealth Edison Co [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	2
Commonwealth Edison Co [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Commonwealth Edison Co [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	5
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	60	50
Accounts Receivable, Related Parties, Current	9	2
PECO Energy Co [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	0
PECO Energy Co [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	2
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	49	61
Accounts Receivable, Related Parties, Current	2	3
Baltimore Gas and Electric Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	0
Baltimore Gas and Electric Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Baltimore Gas and Electric Company [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	2
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	80	104
Accounts Receivable, Related Parties, Current	3	8
Pepco Holdings LLC [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	12	15
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	51	55
Accounts Receivable, Related Parties, Current	0	2
Potomac Electric Power Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	2
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	24	36
Accounts Receivable, Related Parties, Current	1	1
Delmarva Power and Light Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	0
Delmarva Power and Light Company [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	26	31
Accounts Receivable, Related Parties, Current	1	6
Atlantic City Electric Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	6
Business Services Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	229	271
Business Services Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	86	72
Business Services Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	49	59
Business Services Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	25	28
Business Services Company [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	32	47
Business Services Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	4
Business Services Company [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	15	25
Business Services Company [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	21
Business Services Company [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	15
Business Services Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	0
PHI Service Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	33	33
PHI Service Company [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	13	14
PHI Service Company [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	11	10
PHI Service Company [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	9
PHI Service Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Other Legal Entities [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	15	43
Accounts Receivable, Related Parties, Current	49	51
Other Legal Entities [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	23	22
Other Legal Entities [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	6	9
Other Legal Entities [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	4
Other Legal Entities [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	3
Other Legal Entities [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	10	11
Other Legal Entities [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Other Legal Entities [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Other Legal Entities [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 1	$ 1

Related Party Transactions - No

Related Party Transactions - Noncurrent Receivables from/Payables to affiliates (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 3,143	$ 3,017
Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	2,597	2,541
PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 546	$ 475

Related Party Transactions - Lo

Related Party Transactions - Long Term Debt to Financing Trusts (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Long-term debt to financing trust	$ 390	$ 390
ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	206	206
PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	81	81
PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	103	103
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] \| ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] \| PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
Commonwealth Edison Co [Member] \| PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	184	184
PECO Energy Co [Member] \| ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
PECO Energy Co [Member] \| PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	81	81
PECO Energy Co [Member] \| PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	$ 103	$ 103