Commonwealth Edison 10-Q5 May 212021 Q1 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page	3 Months Ended
Cover Page	Mar. 31, 2021shares
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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	977,175,235
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
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	440 South LaSalle Street
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60605-1028
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	127,021,380
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
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
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
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
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
		Mar. 31, 2021	Mar. 31, 2020
Operating revenues
Revenues from alternative revenue programs		$ 129	$ 67
Operating revenues from affiliates		0	1
Total operating revenues		9,890	8,747
Operating expenses
Operating and maintenance		1,979	2,204
Depreciation and amortization		1,697	1,021
Taxes other than income taxes		438	437
Total operating expenses		10,082	7,529
Gain on sales of assets and businesses		71	2
Operating income (loss)		(121)	1,220
Other income and (deductions)
Interest expense, net		(380)	(404)
Interest expense to affiliates		(6)	(6)
Other, net		225	(725)
Total other income and (deductions)		(161)	(1,135)
Income before income taxes		(282)	85
Income taxes		(19)	(294)
Equity in losses of unconsolidated affiliates		(1)	(3)
Net income (loss)		(264)	376
Net income (loss) attributable to noncontrolling interests		25	(206)
Net Income (Loss) Available to Common Stockholders, Basic		(289)	582
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(1)	(10)
Actuarial loss reclassified to periodic benefit cost		56	47
Pension and non-pension postretirement benefit plan valuation adjustment		(2)	(7)
Unrealized (loss) gain on cash flow hedges		0	(1)
Unrealized gain (loss) on foreign currency translation		1	(8)
Other comprehensive income		54	21
Comprehensive income		(210)	397
Comprehensive income (loss) attributable to noncontrolling interests		25	(206)
Comprehensive income attributable to common shareholders/membership interest		$ (235)	$ 603
Average shares of common stock outstanding:
Basic average shares of common stock outstanding		977	975
Assumed exercise and/or distributions of stock-based awards		0	1
Diluted average shares of common stock outstanding	[1]	977	976
(Losses) earnings per average common share
Basic earnings per average common share		$ (0.30)	$ 0.60
Diluted earnings per average common share		$ (0.30)	$ 0.60
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0
Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		$ (289)	$ 582
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		295	330
Total operating revenues		5,559	4,733
Operating expenses
Purchased power and/or fuel from affiliates		0	(6)
Operating and maintenance		856	1,121
Operating and maintenance from affiliates		145	142
Depreciation and amortization		940	304
Taxes other than income taxes		121	129
Total operating expenses		6,672	4,400
Gain on sales of assets and businesses		71	0
Operating income (loss)		(1,042)	333
Other income and (deductions)
Interest expense, net		(68)	(100)
Interest expense to affiliates		(4)	(9)
Other, net		167	(771)
Total other income and (deductions)		95	(880)
Income before income taxes		(947)	(547)
Income taxes		(179)	(389)
Equity in losses of unconsolidated affiliates		(1)	(3)
Net income (loss)		(769)	(161)
Net income (loss) attributable to noncontrolling interests		24	(206)
Net income attributable to membership interest		(793)	45
Other comprehensive income (loss), net of income taxes
Unrealized (loss) gain on cash flow hedges		0	(1)
Unrealized gain (loss) on foreign currency translation		1	(8)
Other comprehensive income		1	(9)
Comprehensive income		(768)	(170)
Comprehensive income (loss) attributable to noncontrolling interests		24	(206)
Comprehensive income attributable to common shareholders/membership interest		(792)	36
Commonwealth Edison Co [Member]
Operating revenues
Revenues from alternative revenue programs		54	12
Operating revenues from affiliates		6	5
Total operating revenues		1,535	1,439
Operating expenses
Purchased power and/or fuel from affiliates		85	97
Operating and maintenance		245	243
Operating and maintenance from affiliates		71	74
Depreciation and amortization		292	273
Taxes other than income taxes		75	75
Total operating expenses		1,210	1,151
Operating income (loss)		325	288
Other income and (deductions)
Interest expense, net		(93)	(91)
Interest expense to affiliates		(3)	(3)
Other, net		7	10
Total other income and (deductions)		(89)	(84)
Income before income taxes		236	204
Income taxes		39	36
Net income (loss)		197	168
Other comprehensive income (loss), net of income taxes
Comprehensive income		197	168
PECO Energy Co [Member]
Operating revenues
Revenues from alternative revenue programs		10	2
Operating revenues from affiliates		2	2
Total operating revenues		889	813
Operating expenses
Purchased power and/or fuel from affiliates		41	36
Operating and maintenance		193	179
Operating and maintenance from affiliates		41	38
Depreciation and amortization		86	86
Taxes other than income taxes		43	39
Total operating expenses		679	625
Operating income (loss)		210	188
Other income and (deductions)
Interest expense, net		(35)	(33)
Interest expense to affiliates		(3)	(3)
Other, net		5	3
Total other income and (deductions)		(33)	(33)
Income before income taxes		177	155
Income taxes		10	15
Net income (loss)		167	140
Other comprehensive income (loss), net of income taxes
Comprehensive income		167	140
PECO Energy Co [Member] \| Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		167	140
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		18	36
Operating revenues from affiliates		6	6
Total operating revenues		974	937
Operating expenses
Purchased power and/or fuel from affiliates		70	98
Operating and maintenance		152	146
Operating and maintenance from affiliates		45	42
Depreciation and amortization		152	143
Taxes other than income taxes		72	69
Total operating expenses		752	688
Operating income (loss)		222	249
Other income and (deductions)
Interest expense, net		(34)	(32)
Other, net		8	5
Total other income and (deductions)		(26)	(27)
Income before income taxes		196	222
Income taxes		(13)	41
Net income (loss)		209	181
Other comprehensive income (loss), net of income taxes
Comprehensive income		209	181
Baltimore Gas and Electric Company [Member] \| Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		209	181
Pepco Holdings LLC [Member]
Operating revenues
Revenues from alternative revenue programs		46	18
Operating revenues from affiliates		3	3
Total operating revenues		1,244	1,171
Operating expenses
Purchased power and/or fuel from affiliates		98	104
Operating and maintenance		216	219
Operating and maintenance from affiliates		40	38
Depreciation and amortization		210	194
Taxes other than income taxes		113	114
Total operating expenses		1,058	1,000
Gain on sales of assets and businesses		0	2
Operating income (loss)		186	173
Other income and (deductions)
Interest expense, net		(67)	(67)
Other, net		17	13
Total other income and (deductions)		(50)	(54)
Income before income taxes		136	119
Income taxes		8	11
Net income (loss)		128	108
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		128	108
Potomac Electric Power Company [Member]
Operating revenues
Revenues from alternative revenue programs		26	15
Operating revenues from affiliates		1	1
Total operating revenues		553	544
Operating expenses
Purchased power and/or fuel from affiliates		74	79
Operating and maintenance		56	60
Operating and maintenance from affiliates		52	51
Depreciation and amortization		102	95
Taxes other than income taxes		90	92
Total operating expenses		466	462
Operating income (loss)		87	82
Other income and (deductions)
Interest expense, net		(34)	(34)
Other, net		12	9
Total other income and (deductions)		(22)	(25)
Income before income taxes		65	57
Income taxes		6	5
Net income (loss)		59	52
Other comprehensive income (loss), net of income taxes
Comprehensive income		59	52
Potomac Electric Power Company [Member] \| Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		59	52
Delmarva Power and Light Company [Member]
Operating revenues
Revenues from alternative revenue programs		9	1
Operating revenues from affiliates		2	2
Total operating revenues		382	350
Operating expenses
Purchased power and/or fuel from affiliates		20	22
Operating and maintenance		44	42
Operating and maintenance from affiliates		39	37
Depreciation and amortization		53	48
Taxes other than income taxes		17	16
Total operating expenses		309	284
Operating income (loss)		73	66
Other income and (deductions)
Interest expense, net		(15)	(16)
Other, net		3	2
Total other income and (deductions)		(12)	(14)
Income before income taxes		61	52
Income taxes		5	7
Net income (loss)		56	45
Other comprehensive income (loss), net of income taxes
Comprehensive income		56	45
Delmarva Power and Light Company [Member] \| Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		56	45
Atlantic City Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		11	1
Operating revenues from affiliates		1	1
Total operating revenues		310	276
Operating expenses
Purchased power and/or fuel from affiliates		4	2
Operating and maintenance		42	45
Operating and maintenance from affiliates		34	33
Depreciation and amortization		47	43
Taxes other than income taxes		2	2
Total operating expenses		282	251
Gain on sales of assets and businesses		0	2
Operating income (loss)		28	27
Other income and (deductions)
Interest expense, net		(15)	(14)
Interest expense to affiliates		0	(1)
Other, net		1	2
Total other income and (deductions)		(14)	(13)
Income before income taxes		14	14
Income taxes		0	1
Net income (loss)		14	13
Other comprehensive income (loss), net of income taxes
Comprehensive income		14	13
Atlantic City Electric Company [Member] \| Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		14	13
Generation commodities and services
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		5,265	4,404
Operating expenses
Purchased power and/or fuel		4,610	2,710
Generation commodities and services \| Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		5,264	4,403
Operating expenses
Purchased power and/or fuel		4,610	2,710
Rate-regulated utility revenues
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,496	4,276
Operating expenses
Purchased power and/or fuel		1,358	1,157
Electricity, US Regulated
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		3,988	3,748
Electricity, US Regulated \| Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,475	1,422
Operating expenses
Purchased power and/or fuel		442	389
Electricity, US Regulated \| PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		649	600
Operating expenses
Purchased power and/or fuel		189	164
Electricity, US Regulated \| Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		620	595
Operating expenses
Purchased power and/or fuel		162	114
Electricity, US Regulated \| Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,124	1,086
Operating expenses
Purchased power and/or fuel		348	300
Electricity, US Regulated \| Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		526	528
Operating expenses
Purchased power and/or fuel		92	85
Electricity, US Regulated \| Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		300	283
Operating expenses
Purchased power and/or fuel		103	88
Electricity, US Regulated \| Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		298	274
Operating expenses
Purchased power and/or fuel		153	126
Natural Gas, US Regulated
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		637	595
Natural Gas, US Regulated \| PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		228	209
Operating expenses
Purchased power and/or fuel		86	83
Natural Gas, US Regulated \| Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		330	300
Operating expenses
Purchased power and/or fuel		99	76
Natural Gas, US Regulated \| Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		71	64
Operating expenses
Purchased power and/or fuel		33	31
Natural Gas, US Regulated \| Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		71	64
Operating expenses
Purchased power and/or fuel		$ 33	$ 31

[1]	The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was less than 1 million for the three months ended March 31, 2021 and March 31, 2020.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income (loss)	$ (264)	$ 376
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	2,104	1,378
Asset impairments	1	8
Gain on sales of assets and businesses	(71)	0
Deferred income taxes and amortization of investment tax credits	(142)	(245)
Net fair value changes related to derivatives	(178)	(132)
Net realized and unrealized (gains) losses on NDT funds	(118)	651
Unrealized loss on equity investments	23	0
Other non-cash operating activities	(170)	273
Changes in assets and liabilities:
Accounts receivable	(372)	800
Inventories	77	81
Accounts payable and accrued expenses	(176)	(976)
Option premiums received (paid), net	16	(38)
Collateral received (posted), net	273	(21)
Income taxes	113	(56)
Pension and non-pension postretirement benefit contributions	(537)	(531)
Other assets and liabilities	(1,840)	(488)
Net cash flows provided by operating activities	(1,261)	1,080
Cash flows from investing activities
Capital expenditures	(2,140)	(2,016)
Proceeds from NDT fund sales	2,908	1,183
Investment in NDT funds	(2,939)	(1,234)
Collection of deferred purchase price	1,574	0
Proceeds from sales of assets and businesses	680	0
Other investing activities	12	(8)
Net cash flows provided by (used in) investing activities	95	(2,075)
Cash flows from financing activities
Changes in short-term borrowings	597	109
Proceeds from short-term borrowings with maturities greater than 90 days	500	500
Issuance of long-term debt	1,705	2,652
Retirement of long-term debt	(79)	(1,032)
Dividends paid on common stock	(374)	(373)
Proceeds from employee stock plans	31	30
Other financing activities	(46)	(21)
Net cash flows provided by (used in) financing activities	2,334	1,865
Increase (Decrease) in cash, restricted cash, and cash equivalents	1,168	870
Cash, restricted cash, and cash equivalents at beginning of period	1,166	1,122
Cash, restricted cash, and cash equivalents at end of period	2,334	1,992
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(324)	(180)
Increase in deferred purchase price	1,339	0
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(769)	(161)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	1,346	661
Asset impairments	1	8
Gain on sales of assets and businesses	(71)	0
Deferred income taxes and amortization of investment tax credits	(123)	(329)
Net fair value changes related to derivatives	(178)	(127)
Net realized and unrealized (gains) losses on NDT funds	(118)	651
Unrealized loss on equity investments	23	0
Other non-cash operating activities	(202)	205
Changes in assets and liabilities:
Accounts receivable	(453)	787
Receivables from and payables to affiliates, net	59	34
Inventories	50	39
Accounts payable and accrued expenses	208	(614)
Option premiums received (paid), net	16	(38)
Collateral received (posted), net	270	(22)
Income taxes	(55)	(58)
Pension and non-pension postretirement benefit contributions	(205)	(232)
Other assets and liabilities	(1,411)	(184)
Net cash flows provided by operating activities	(1,612)	620
Cash flows from investing activities
Capital expenditures	(382)	(558)
Proceeds from NDT fund sales	2,908	1,183
Investment in NDT funds	(2,939)	(1,234)
Collection of deferred purchase price	1,574	0
Proceeds from sales of assets and businesses	680	0
Changes in Exelon/PHI intercompany money pool	0	(254)
Other investing activities	(2)	(8)
Net cash flows provided by (used in) investing activities	1,839	(871)
Cash flows from financing activities
Changes in short-term borrowings	997	275
Proceeds from short-term borrowings with maturities greater than 90 days	0	500
Issuance of long-term debt	1	1,502
Retirement of long-term debt	(35)	(1,028)
Changes in Exelon/PHI intercompany money pool	(285)	0
Distributions to member	(458)	(468)
Other financing activities	(12)	(8)
Net cash flows provided by (used in) financing activities	208	773
Increase (Decrease) in cash, restricted cash, and cash equivalents	435	522
Cash, restricted cash, and cash equivalents at beginning of period	327	449
Cash, restricted cash, and cash equivalents at end of period	762	971
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(37)	(56)
Increase in deferred purchase price	1,339	0
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	197	168
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	292	273
Deferred income taxes and amortization of investment tax credits	63	42
Other non-cash operating activities	(9)	16
Changes in assets and liabilities:
Accounts receivable	23	9
Receivables from and payables to affiliates, net	(15)	(6)
Inventories	(1)	(2)
Accounts payable and accrued expenses	(176)	(147)
Collateral received (posted), net	5	3
Income taxes	(23)	(7)
Pension and non-pension postretirement benefit contributions	(171)	(143)
Other assets and liabilities	(159)	(132)
Net cash flows provided by operating activities	26	74
Cash flows from investing activities
Capital expenditures	(613)	(506)
Other investing activities	7	5
Net cash flows provided by (used in) investing activities	(606)	(501)
Cash flows from financing activities
Changes in short-term borrowings	(188)	(130)
Issuance of long-term debt	700	1,000
Dividends paid on common stock	(127)	(125)
Contributions from parent	198	125
Other financing activities	(9)	(13)
Net cash flows provided by (used in) financing activities	574	857
Increase (Decrease) in cash, restricted cash, and cash equivalents	(6)	430
Cash, restricted cash, and cash equivalents at beginning of period	405	403
Cash, restricted cash, and cash equivalents at end of period	399	833
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(107)	(5)
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	167	140
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	86	86
Deferred income taxes and amortization of investment tax credits	6	2
Other non-cash operating activities	12	22
Changes in assets and liabilities:
Accounts receivable	(5)	14
Receivables from and payables to affiliates, net	(2)	(3)
Inventories	13	15
Accounts payable and accrued expenses	(36)	(45)
Income taxes	3	14
Pension and non-pension postretirement benefit contributions	(16)	(16)
Other assets and liabilities	(103)	(84)
Net cash flows provided by operating activities	125	145
Cash flows from investing activities
Capital expenditures	(295)	(259)
Changes in Exelon/PHI intercompany money pool	(48)	(22)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(342)	(280)
Cash flows from financing activities
Issuance of long-term debt	375	0
Changes in Exelon/PHI intercompany money pool	(40)	0
Dividends paid on common stock	(85)	(85)
Contributions from parent	0	231
Other financing activities	(4)	0
Net cash flows provided by (used in) financing activities	246	146
Increase (Decrease) in cash, restricted cash, and cash equivalents	29	11
Cash, restricted cash, and cash equivalents at beginning of period	26	27
Cash, restricted cash, and cash equivalents at end of period	55	38
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(44)	(11)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	209	181
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	152	143
Deferred income taxes and amortization of investment tax credits	(4)	33
Other non-cash operating activities	2	(8)
Changes in assets and liabilities:
Accounts receivable	12	(28)
Receivables from and payables to affiliates, net	(15)	(13)
Inventories	9	20
Accounts payable and accrued expenses	(59)	(9)
Income taxes	(9)	7
Pension and non-pension postretirement benefit contributions	(65)	(64)
Other assets and liabilities	(103)	10
Net cash flows provided by operating activities	129	272
Cash flows from investing activities
Capital expenditures	(336)	(283)
Other investing activities	2	(6)
Net cash flows provided by (used in) investing activities	(334)	(289)
Cash flows from financing activities
Changes in short-term borrowings	156	66
Dividends paid on common stock	(74)	(62)
Net cash flows provided by (used in) financing activities	82	4
Increase (Decrease) in cash, restricted cash, and cash equivalents	(123)	(13)
Cash, restricted cash, and cash equivalents at beginning of period	145	25
Cash, restricted cash, and cash equivalents at end of period	22	12
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(80)	(35)
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	128	108
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	210	194
Deferred income taxes and amortization of investment tax credits	4	(4)
Other non-cash operating activities	(25)	7
Changes in assets and liabilities:
Accounts receivable	56	36
Receivables from and payables to affiliates, net	(18)	(17)
Inventories	5	8
Accounts payable and accrued expenses	(24)	(16)
Income taxes	3	15
Pension and non-pension postretirement benefit contributions	(36)	(27)
Other assets and liabilities	(94)	(72)
Net cash flows provided by operating activities	209	232
Cash flows from investing activities
Capital expenditures	(456)	(376)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(455)	(375)
Cash flows from financing activities
Changes in short-term borrowings	(368)	(100)
Issuance of long-term debt	625	150
Retirement of long-term debt	(44)	(6)
Changes in Exelon/PHI intercompany money pool	3	7
Distributions to member	(81)	(134)
Contributions from member	560	144
Other financing activities	(5)	(1)
Net cash flows provided by (used in) financing activities	690	60
Increase (Decrease) in cash, restricted cash, and cash equivalents	444	(83)
Cash, restricted cash, and cash equivalents at beginning of period	160	181
Cash, restricted cash, and cash equivalents at end of period	604	98
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(33)	(57)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	59	52
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	102	95
Deferred income taxes and amortization of investment tax credits	4	(2)
Other non-cash operating activities	(25)	(11)
Changes in assets and liabilities:
Accounts receivable	26	14
Receivables from and payables to affiliates, net	(9)	(11)
Inventories	1	3
Accounts payable and accrued expenses	0	6
Income taxes	2	6
Pension and non-pension postretirement benefit contributions	(5)	(4)
Other assets and liabilities	(58)	(38)
Net cash flows provided by operating activities	97	110
Cash flows from investing activities
Capital expenditures	(220)	(180)
Changes in Exelon/PHI intercompany money pool	0	(114)
Other investing activities	1	(4)
Net cash flows provided by (used in) investing activities	(219)	(298)
Cash flows from financing activities
Changes in short-term borrowings	(35)	(82)
Issuance of long-term debt	150	150
Dividends paid on common stock	(28)	(28)
Contributions from parent	138	137
Other financing activities	(1)	(1)
Net cash flows provided by (used in) financing activities	224	176
Increase (Decrease) in cash, restricted cash, and cash equivalents	102	(12)
Cash, restricted cash, and cash equivalents at beginning of period	65	63
Cash, restricted cash, and cash equivalents at end of period	167	51
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(16)	(43)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	56	45
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	53	48
Deferred income taxes and amortization of investment tax credits	2	0
Other non-cash operating activities	(1)	2
Changes in assets and liabilities:
Accounts receivable	15	14
Receivables from and payables to affiliates, net	(11)	(9)
Inventories	2	3
Accounts payable and accrued expenses	11	4
Income taxes	3	7
Other assets and liabilities	(26)	(10)
Net cash flows provided by operating activities	104	104
Cash flows from investing activities
Capital expenditures	(112)	(95)
Other investing activities	0	(4)
Net cash flows provided by (used in) investing activities	(112)	(99)
Cash flows from financing activities
Changes in short-term borrowings	(146)	(2)
Issuance of long-term debt	125	0
Changes in Exelon/PHI intercompany money pool	0	37
Dividends paid on common stock	(40)	(52)
Contributions from parent	120	6
Other financing activities	(2)	0
Net cash flows provided by (used in) financing activities	57	(11)
Increase (Decrease) in cash, restricted cash, and cash equivalents	49	(6)
Cash, restricted cash, and cash equivalents at beginning of period	15	13
Cash, restricted cash, and cash equivalents at end of period	64	7
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(15)	(9)
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	14	13
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	47	43
Deferred income taxes and amortization of investment tax credits	(1)	(1)
Other non-cash operating activities	(7)	4
Changes in assets and liabilities:
Accounts receivable	13	11
Receivables from and payables to affiliates, net	1	3
Inventories	3	2
Accounts payable and accrued expenses	(11)	3
Income taxes	1	2
Pension and non-pension postretirement benefit contributions	(3)	(2)
Other assets and liabilities	(3)	(22)
Net cash flows provided by operating activities	54	56
Cash flows from investing activities
Capital expenditures	(123)	(101)
Other investing activities	0	6
Net cash flows provided by (used in) investing activities	(123)	(95)
Cash flows from financing activities
Changes in short-term borrowings	(187)	(16)
Issuance of long-term debt	350	0
Retirement of long-term debt	(44)	(5)
Changes in Exelon/PHI intercompany money pool	0	77
Dividends paid on common stock	(14)	(23)
Contributions from parent	303	1
Other financing activities	(3)	0
Net cash flows provided by (used in) financing activities	405	34
Increase (Decrease) in cash, restricted cash, and cash equivalents	336	(5)
Cash, restricted cash, and cash equivalents at beginning of period	30	28
Cash, restricted cash, and cash equivalents at end of period	366	23
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (2)	$ (4)

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) shares in Millions, $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents		$ 1,908	$ 663
Restricted cash and cash equivalents		374	438
Accounts receivable
Customer accounts receivable		4,017	3,597
Customer allowance for credit losses		(442)	(366)
Customer accounts receivable, net		3,575	3,231
Other accounts receivable		1,320	1,469
Other allowance for credit losses		(79)	(71)
Other accounts receivable, net		1,241	1,398
Mark-to-market derivative assets, current		568	644
Unamortized energy contract assets, current		38	38
Inventories, net
Fossil fuel and emission allowances		205	297
Materials and supplies		1,427	1,425
Regulatory assets, current		1,269	1,228
Renewable energy credits, current		694	633
Assets held for sale		11	958
Other		1,687	1,609
Total current assets		12,997	12,562
Property, plant and equipment, net		82,588	82,584
Accumulated depreciation and amortization		28,121	26,727
Deferred debits and other assets
Regulatory assets, noncurrent		8,810	8,759
Nuclear decommissioning trust funds		14,688	14,464
Investments		431	440
Goodwill		6,677	6,677
Mark-to-market derivative assets, noncurrent		491	555
Unamortized energy contract assets, noncurrent		285	294
Other		3,033	2,982
Total deferred debits and other assets		34,415	34,171
Total assets	[1]	130,000	129,317
Current Liabilities
Short-term borrowings		3,128	2,031
Long-term debt due within one year		2,281	1,819
Accounts payable		3,430	3,562
Accrued expenses		1,729	2,078
Payables to affiliates, current		5	5
Regulatory liabilities, current		663	581
Mark-to-market derivative liabilities, current		422	295
Unamortized energy contract liabilities, current		98	100
Renewable energy credit obligation		645	661
Liabilities held for sale		3	375
Other		1,176	1,264
Total current liabilities		13,580	12,771
Long-term debt		36,248	35,093
Long-term debt to financing trusts		390	390
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,129	13,035
Asset retirement obligations, noncurrent		12,405	12,300
Pension obligations		3,951	4,503
Non-pension postretirement benefit obligations		1,988	2,011
Spent nuclear fuel obligation		1,208	1,208
Regulatory liabilities, noncurrent		9,130	9,485
Mark-to-market derivative liabilities, noncurrent		453	473
Unamortized energy contract liabilities, noncurrent		217	238
Other		2,988	2,942
Total deferred credits and other liabilities		45,469	46,195
Total liabilities	[1]	95,687	94,449
Commitments and contingencies
Common Stock, No Par Value		$ 0	$ 0
Shareholders' equity
Common stock, shares authorized		2,000	2,000
Common stock, shares outstanding		977	976
Common stock		$ 19,412	$ 19,373
Treasury stock, shares		2	2
Treasury stock, at cost		$ (123)	$ (123)
Retained earnings/Undistributed earnings (losses)		16,072	16,735
Accumulated other comprehensive loss, net		(3,346)	(3,400)
Total shareholders’ equity		32,015	32,585
Member’s equity
Noncontrolling interests		2,298	2,283
Total equity		34,313	34,868
Total liabilities and shareholders’ equity		130,000	129,317
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		175	98
Restricted cash and cash equivalents		37	47
Accounts receivable
Customer accounts receivable, net		145	148
Unamortized energy contract assets, current		22	22
Inventories, net
Materials and supplies		242	244
Assets held for sale		0	101
Other		448	674
Total current assets		1,104	1,370
Property, plant and equipment, net		5,747	5,803
Deferred debits and other assets
Nuclear decommissioning trust funds		3,089	3,007
Unamortized energy contract assets, noncurrent		243	249
Other		47	52
Total assets		10,230	10,481
Current Liabilities
Long-term debt due within one year		90	94
Accounts payable		95	81
Accrued expenses		67	70
Unamortized energy contract liabilities, current		3	4
Liabilities held for sale		0	16
Other		1	5
Total current liabilities		256	270
Long-term debt		861	889
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		2,347	2,318
Other		116	129
Total liabilities		3,580	3,606
Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		9,985	10,200
Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		3,578	3,598
Exelon Generation Co L L C [Member]
Current Assets
Cash and cash equivalents		721	226
Restricted cash and cash equivalents		41	89
Accounts receivable
Customer accounts receivable		1,857	1,330
Customer allowance for credit losses		(65)	(32)
Customer accounts receivable, net		1,792	1,298
Other accounts receivable		348	352
Other accounts receivable, net		348	352
Mark-to-market derivative assets, current		569	644
Receivables from affiliates, current		106	153
Unamortized energy contract assets, current		38	38
Inventories, net
Fossil fuel and emission allowances		175	233
Materials and supplies		973	978
Renewable energy credits, current		676	621
Assets held for sale		11	958
Other		1,290	1,357
Total current assets		6,740	6,947
Property, plant and equipment, net		21,311	22,214
Accumulated depreciation and amortization		14,355	13,370
Deferred debits and other assets
Nuclear decommissioning trust funds		14,688	14,464
Investments		178	184
Goodwill		47	47
Mark-to-market derivative assets, noncurrent		491	555
Prepaid pension asset		1,736	1,558
Unamortized energy contract assets, noncurrent		285	293
Deferred income taxes		15	6
Other		1,835	1,826
Total deferred debits and other assets		19,275	18,933
Total assets	[2]	47,326	48,094
Current Liabilities
Short-term borrowings		1,837	840
Long-term debt due within one year		699	197
Accounts payable		1,529	1,253
Accrued expenses		692	788
Payables to affiliates, current		125	107
Borrowings from Exelon/PHI intercompany money pool		0	285
Mark-to-market derivative liabilities, current		392	262
Unamortized energy contract liabilities, current		5	7
Renewable energy credit obligation		645	661
Liabilities held for sale		3	375
Other		371	444
Total current liabilities		6,298	5,219
Long-term debt		5,038	5,566
Long-term debt to affiliates		323	324
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		3,542	3,656
Asset retirement obligations, noncurrent		12,157	12,054
Non-pension postretirement benefit obligations		857	858
Spent nuclear fuel obligation		1,208	1,208
Payables to affiliates, noncurrent		2,865	3,017
Mark-to-market derivative liabilities, noncurrent		190	205
Unamortized energy contract liabilities, noncurrent		3	3
Other		1,405	1,308
Total deferred credits and other liabilities		22,227	22,309
Total liabilities	[2]	33,886	33,418
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		1,554	2,805
Accumulated other comprehensive loss, net		(29)	(30)
Member’s equity
Membership interest		9,624	9,624
Total members' equity		11,149	12,399
Noncontrolling interests		2,291	2,277
Total equity		13,440	14,676
Total liabilities and shareholders’ equity		47,326	48,094
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		175	98
Restricted cash and cash equivalents		33	44
Accounts receivable
Customer accounts receivable, net		145	148
Unamortized energy contract assets, current		22	22
Inventories, net
Materials and supplies		242	244
Assets held for sale		0	101
Other		443	669
Total current assets		1,095	1,362
Property, plant and equipment, net		5,747	5,803
Deferred debits and other assets
Nuclear decommissioning trust funds		3,089	3,007
Unamortized energy contract assets, noncurrent		243	249
Other		38	42
Total assets		10,212	10,463
Current Liabilities
Long-term debt due within one year		69	68
Accounts payable		95	81
Accrued expenses		67	70
Unamortized energy contract liabilities, current		3	4
Liabilities held for sale		0	16
Other		1	5
Total current liabilities		235	244
Long-term debt		861	889
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		2,347	2,318
Other		116	129
Total liabilities		3,559	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		9,967	10,182
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		3,557	3,572
Commonwealth Edison Co [Member]
Current Assets
Cash and cash equivalents		86	83
Restricted cash and cash equivalents		270	279
Accounts receivable
Customer accounts receivable		626	656
Customer allowance for credit losses		(103)	(97)
Customer accounts receivable, net		523	559
Other accounts receivable		243	239
Other allowance for credit losses		(22)	(21)
Other accounts receivable, net		221	218
Receivables from affiliates, current		21	22
Inventories, net
Inventories, net		170	170
Regulatory assets, current		294	279
Other		55	49
Total current assets		1,640	1,659
Property, plant and equipment, net		24,840	24,557
Accumulated depreciation and amortization		5,811	5,672
Deferred debits and other assets
Regulatory assets, noncurrent		1,840	1,749
Investments		6	6
Goodwill		2,625	2,625
Receivables from affiliates, noncurrent		2,375	2,541
Prepaid pension asset		1,165	1,022
Other		334	307
Total deferred debits and other assets		8,345	8,250
Total assets		34,825	34,466
Current Liabilities
Short-term borrowings		135	323
Long-term debt due within one year		350	350
Accounts payable		533	683
Accrued expenses		242	390
Payables to affiliates, current		80	96
Customer deposits		84	86
Regulatory liabilities, current		360	289
Mark-to-market derivative liabilities, current		31	33
Other		128	143
Total current liabilities		1,943	2,393
Long-term debt		9,324	8,633
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,427	4,341
Asset retirement obligations, noncurrent		127	126
Non-pension postretirement benefit obligations		177	173
Regulatory liabilities, noncurrent		6,172	6,403
Mark-to-market derivative liabilities, noncurrent		264	268
Other		589	595
Total deferred credits and other liabilities		11,756	11,906
Total liabilities		23,228	23,137
Commitments and contingencies
Shareholders' equity
Common stock		1,588	1,588
Other paid-in capital		8,483	8,285
Retained deficit unappropriated		(1,639)	(1,639)
Retained earnings appropriated		3,165	3,095
Total shareholders’ equity		11,597	11,329
Member’s equity
Total liabilities and shareholders’ equity		34,825	34,466
PECO Energy Co [Member]
Current Assets
Cash and cash equivalents		48	19
Restricted cash and cash equivalents		7	7
Accounts receivable
Customer accounts receivable		499	511
Customer allowance for credit losses		(130)	(116)
Customer accounts receivable, net		369	395
Other accounts receivable		140	130
Other allowance for credit losses		(11)	(8)
Other accounts receivable, net		129	122
Receivables from affiliates, current		0	2
Receivable from Exelon/PHI intercompany money pool		48	0
Inventories, net
Fossil fuel and emission allowances		15	33
Materials and supplies		43	38
Prepaid utility taxes		103	0
Regulatory assets, current		29	25
Other		22	21
Total current assets		813	662
Property, plant and equipment, net		10,352	10,181
Accumulated depreciation and amortization		3,897	3,843
Deferred debits and other assets
Regulatory assets, noncurrent		828	776
Investments		30	30
Receivables from affiliates, noncurrent		490	475
Prepaid pension asset		389	375
Other		35	32
Total deferred debits and other assets		1,772	1,688
Total assets		12,937	12,531
Current Liabilities
Long-term debt due within one year		300	300
Accounts payable		431	479
Accrued expenses		100	129
Payables to affiliates, current		46	50
Borrowings from Exelon/PHI intercompany money pool		0	40
Customer deposits		54	59
Regulatory liabilities, current		127	121
Other		31	30
Total current liabilities		1,089	1,208
Long-term debt		3,825	3,453
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,297	2,242
Asset retirement obligations, noncurrent		29	29
Non-pension postretirement benefit obligations		286	286
Regulatory liabilities, noncurrent		519	503
Other		93	93
Total deferred credits and other liabilities		3,224	3,153
Total liabilities		8,322	7,998
Commitments and contingencies
Shareholders' equity
Common stock		3,014	3,014
Retained earnings/Undistributed earnings (losses)		1,601	1,519
Total shareholders’ equity		4,615	4,533
Member’s equity
Total liabilities and shareholders’ equity		12,937	12,531
Baltimore Gas and Electric Company [Member]
Current Assets
Cash and cash equivalents		21	144
Restricted cash and cash equivalents		1	1
Accounts receivable
Customer accounts receivable		476	487
Customer allowance for credit losses		(43)	(35)
Customer accounts receivable, net		433	452
Other accounts receivable		125	117
Other allowance for credit losses		(9)	(9)
Other accounts receivable, net		116	108
Receivables from affiliates, current		0	3
Inventories, net
Fossil fuel and emission allowances		12	25
Materials and supplies		45	41
Prepaid utility taxes		43	0
Regulatory assets, current		179	168
Other		9	6
Total current assets		859	948
Property, plant and equipment, net		10,026	9,872
Accumulated depreciation and amortization		4,115	4,034
Deferred debits and other assets
Regulatory assets, noncurrent		481	481
Investments		10	10
Prepaid pension asset		314	270
Other		69	69
Total deferred debits and other assets		874	830
Total assets		11,759	11,650
Current Liabilities
Short-term borrowings		156	0
Long-term debt due within one year		300	300
Accounts payable		266	346
Accrued expenses		142	205
Payables to affiliates, current		43	61
Customer deposits		105	110
Regulatory liabilities, current		41	30
Other		83	91
Total current liabilities		1,136	1,143
Long-term debt		3,365	3,364
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,609	1,521
Asset retirement obligations, noncurrent		24	23
Non-pension postretirement benefit obligations		182	189
Regulatory liabilities, noncurrent		1,016	1,109
Other		95	104
Total deferred credits and other liabilities		2,926	2,946
Total liabilities		7,427	7,453
Commitments and contingencies
Shareholders' equity
Common stock		2,318	2,318
Retained earnings/Undistributed earnings (losses)		2,014	1,879
Total shareholders’ equity		4,332	4,197
Member’s equity
Total liabilities and shareholders’ equity		11,759	11,650
Pepco Holdings LLC [Member]
Current Assets
Cash and cash equivalents		558	111
Restricted cash and cash equivalents		37	39
Accounts receivable
Customer accounts receivable		557	611
Customer allowance for credit losses		(101)	(86)
Customer accounts receivable, net		456	525
Other accounts receivable		261	260
Other allowance for credit losses		(37)	(33)
Other accounts receivable, net		224	227
Receivables from affiliates, current		0	8
Inventories, net
Fossil fuel and emission allowances		3	6
Materials and supplies		196	198
Regulatory assets, current		450	440
Other		52	45
Total current assets		1,976	1,599
Property, plant and equipment, net		15,651	15,377
Accumulated depreciation and amortization		1,930	1,811
Deferred debits and other assets
Regulatory assets, noncurrent		1,912	1,933
Investments		141	140
Goodwill		4,005	4,005
Prepaid pension asset		383	365
Deferred income taxes		9	10
Other		310	307
Total deferred debits and other assets		6,760	6,760
Total assets	[3]	24,387	23,736
Current Liabilities
Short-term borrowings		0	368
Long-term debt due within one year		304	347
Accounts payable		503	539
Accrued expenses		279	299
Payables to affiliates, current		78	104
Borrowings from Exelon/PHI intercompany money pool		24	21
Customer deposits		96	106
Regulatory liabilities, current		130	137
Unamortized energy contract liabilities, current		92	92
Other		137	141
Total current liabilities		1,643	2,154
Long-term debt		7,273	6,659
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,481	2,439
Asset retirement obligations, noncurrent		59	59
Non-pension postretirement benefit obligations		80	86
Regulatory liabilities, noncurrent		1,391	1,438
Unamortized energy contract liabilities, noncurrent		214	235
Other		595	622
Total deferred credits and other liabilities		4,820	4,879
Total liabilities	[3]	13,736	13,692
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		(21)	(68)
Member’s equity
Membership interest		10,672	10,112
Total members' equity		10,651	10,044
Total equity		10,651	10,044
Total liabilities and shareholders’ equity		24,387	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		4	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		5	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		21	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		21	26
Long-term debt		0	0
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total liabilities		21	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		21	26
Potomac Electric Power Company [Member]
Current Assets
Cash and cash equivalents		134	30
Restricted cash and cash equivalents		33	35
Accounts receivable
Customer accounts receivable		252	279
Customer allowance for credit losses		(41)	(32)
Customer accounts receivable, net		211	247
Other accounts receivable		138	131
Other allowance for credit losses		(15)	(13)
Other accounts receivable, net		123	118
Receivables from affiliates, current		0	2
Inventories, net
Inventories, net		110	111
Regulatory assets, current		224	214
Other		19	13
Total current assets		854	770
Property, plant and equipment, net		7,606	7,456
Accumulated depreciation and amortization		3,746	3,697
Deferred debits and other assets
Regulatory assets, noncurrent		563	570
Investments		116	115
Prepaid pension asset		283	284
Other		71	69
Total deferred debits and other assets		1,033	1,038
Total assets		9,493	9,264
Current Liabilities
Short-term borrowings		0	35
Long-term debt due within one year		4	3
Accounts payable		213	226
Accrued expenses		165	164
Payables to affiliates, current		44	55
Customer deposits		45	51
Regulatory liabilities, current		39	46
Merger related obligation		33	33
Current portion of DC PLUG obligation		30	30
Other		30	31
Total current liabilities		603	674
Long-term debt		3,313	3,162
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,209	1,189
Asset retirement obligations, noncurrent		39	39
Non-pension postretirement benefit obligations		9	13
Regulatory liabilities, noncurrent		624	644
Other		324	340
Total deferred credits and other liabilities		2,205	2,225
Total liabilities		6,121	6,061
Commitments and contingencies
Shareholders' equity
Common stock		2,196	2,058
Retained earnings/Undistributed earnings (losses)		1,176	1,145
Total shareholders’ equity		3,372	3,203
Member’s equity
Total liabilities and shareholders’ equity		9,493	9,264
Delmarva Power and Light Company [Member]
Current Assets
Cash and cash equivalents		64	15
Restricted cash and cash equivalents		0	0
Accounts receivable
Customer accounts receivable		160	176
Customer allowance for credit losses		(25)	(22)
Customer accounts receivable, net		135	154
Other accounts receivable		66	68
Other allowance for credit losses		(10)	(9)
Other accounts receivable, net		56	59
Receivables from affiliates, current		0	1
Inventories, net
Fossil fuel and emission allowances		2	6
Materials and supplies		53	51
Prepaid utility taxes		10	11
Regulatory assets, current		65	58
Renewable energy credits, current		14	10
Other		2	3
Total current assets		401	368
Property, plant and equipment, net		4,368	4,314
Accumulated depreciation and amortization		1,563	1,533
Deferred debits and other assets
Regulatory assets, noncurrent		226	222
Goodwill		8	8
Prepaid pension asset		161	162
Other		68	66
Total deferred debits and other assets		463	458
Total assets		5,232	5,140
Current Liabilities
Short-term borrowings		0	146
Long-term debt due within one year		82	82
Accounts payable		119	126
Accrued expenses		49	46
Payables to affiliates, current		24	36
Customer deposits		30	32
Regulatory liabilities, current		49	47
Other		19	20
Total current liabilities		372	535
Long-term debt		1,720	1,595
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		734	715
Asset retirement obligations, noncurrent		14	14
Non-pension postretirement benefit obligations		14	15
Regulatory liabilities, noncurrent		474	493
Other		92	97
Total deferred credits and other liabilities		1,328	1,334
Total liabilities		3,420	3,464
Commitments and contingencies
Shareholders' equity
Common stock		1,209	1,089
Retained earnings/Undistributed earnings (losses)		603	587
Total shareholders’ equity		1,812	1,676
Member’s equity
Total liabilities and shareholders’ equity		5,232	5,140
Atlantic City Electric Company [Member]
Current Assets
Cash and cash equivalents		353	17
Restricted cash and cash equivalents		4	3
Accounts receivable
Customer accounts receivable		146	156
Customer allowance for credit losses		(35)	(32)
Customer accounts receivable, net		111	124
Other accounts receivable		69	72
Other allowance for credit losses		(12)	(11)
Other accounts receivable, net		57	61
Receivables from affiliates, current		1	6
Inventories, net
Inventories, net		34	37
Regulatory assets, current		69	75
Other		2	3
Total current assets		631	326
Property, plant and equipment, net		3,552	3,475
Accumulated depreciation and amortization		1,329	1,303
Deferred debits and other assets
Regulatory assets, noncurrent		407	395
Prepaid pension asset		39	40
Other		50	50
Total deferred debits and other assets		496	485
Total assets	[4]	4,679	4,286
Current Liabilities
Short-term borrowings		0	187
Long-term debt due within one year		218	261
Accounts payable		162	177
Accrued expenses		48	46
Payables to affiliates, current		27	31
Customer deposits		21	23
Regulatory liabilities, current		41	44
Other		9	11
Total current liabilities		526	780
Long-term debt		1,500	1,152
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		629	624
Non-pension postretirement benefit obligations		16	17
Regulatory liabilities, noncurrent		266	274
Other		48	48
Total deferred credits and other liabilities		959	963
Total liabilities	[4]	2,985	2,895
Commitments and contingencies
Shareholders' equity
Common stock		1,574	1,271
Retained earnings/Undistributed earnings (losses)		120	120
Total shareholders’ equity		1,694	1,391
Member’s equity
Total liabilities and shareholders’ equity		4,679	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		4	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		4	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		13	13
Current Liabilities
Long-term debt due within one year		16	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		16	21
Long-term debt		0	0
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total liabilities		16	21
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		13	13
Atlantic City Electric Company [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		$ 16	$ 21

[1]	Exelon’s consolidated assets include $9,985 million and $10,200 million at March 31, 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 $3,578 million and $3,598 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,967 million and $10,182 million at March 31, 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 $3,557 million and $3,572 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both March 31, 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 $21 million and $26 million at March 31, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $13 million at both March 31, 2021 and December 31, 2020, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $16 million and $21 million at March 31, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 16 — 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	Common Stock [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]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]	Exelon Generation Co L L C [Member]Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Retained Earnings [Member]	Commonwealth Edison Co [Member]Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member]Other Paid-in-Capital [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]Membership Interest [Member]	Pepco Holdings LLC [Member]Retained Earnings, Unappropriated [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	$ (32)	$ 2,346	$ 9,566	$ 3,950													$ 9,608	$ 9,618	$ (10)
Beginning Balance at Dec. 31, 2019												$ 10,677	$ 1,588		$ (1,639)	$ 7,572	$ 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)		(206)		45	168			168			140		140	181		181	108		108	52		52	45		45	13		13
Long -Term Incentive Plan Activity (shares)	1,354
Lont-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)	(9)	0		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	(41)	2,129	9,568	3,527													9,726	9,762	(36)
Ending Balance at Mar. 31, 2020												10,845	1,588		(1,639)	7,697	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
Appropriation of retained earnings for future dividends														$ 0	(168)		168
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	(30)	2,277	9,624	2,805													10,044	10,112	(68)
Beginning Balance at Dec. 31, 2020	32,585											11,329	1,588		(1,639)	8,285	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)		24		(793)	197			197			167		167	209		209	128		128	59		59	56		56	14		14
Long -Term Incentive Plan Activity (shares)	640
Lont-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	1	0		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	$ (29)	$ 2,291	$ 9,624	$ 1,554													$ 10,651	$ 10,672	$ (21)
Ending Balance at Mar. 31, 2021	$ 32,015											11,597	$ 1,588		(1,639)	$ 8,483	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
Appropriation of retained earnings for future dividends												$ 3,165		$ 0	$ (197)		$ 197

Significant Accounting Policies

Significant Accounting Policies (All Registrants)	3 Months Ended
Significant Accounting Policies (All Registrants)	Mar. 31, 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” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of March 31, 2021 and for the three months ended March 31, 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, except as otherwise disclosed. The

Mergers, Acquisitions, and Disp

Mergers, Acquisitions, and Dispositions (Exelon and Generation)	3 Months Ended
	Mar. 31, 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) Generation owns 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 16 — 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 has 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. The Put Option Agreement’s terms also provide that in the event the put closing has not been completed prior to the 18-month anniversary of the exercise date, EDF may withdraw its exercise notice. In the event of a withdrawal, EDF retains the right to exercise the put option until the later of June 30, 2022 and 18 months following the date of withdrawal, but in no event later than January 1, 2024. EDF is not entitled to this withdrawal right in the event it breaches any provision of the Put Option Agreement that results in the failure of the put to close on or before the 18-month anniversary of the exercise date. The Put Option Agreement provides that the purchase price is to be determined by agreement of the parties, or absent such agreement, by a third-party arbitration process. The third parties determining fair market value of EDF’s 49.99% interest are to take into consideration all rights and obligations under the LLC Operating Agreement and Employee Matters Agreement including but not limited to Generation’s rights with respect to any unpaid aggregate preferred distributions and the related return. As of March 31, 2021, the total unpaid aggregate preferred distributions and related return owed to Generation is $632 million. 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. At this time, Generation cannot reasonably predict the ultimate purchase price that will be paid to EDF for its interest in CENG. The transaction required approval by the FERC and the NYPSC, which approvals were received on July 30, 2020 and April 15, 2021, respectively. The sale process is currently expected to close in the second half of 2021. 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. Completion of the transaction is expected in the second half of 2021 and is subject to various customary closing conditions. As a result, in the second quarter of 2021, Exelon and Generation will reclassify these assets and liabilities as held for sale and expect to record an impairment loss in a range of $135 million to $150 million on a pre-tax basis, which will be recorded within Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	3 Months Ended
Regulatory Matters (All Registrants)	Mar. 31, 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 the 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 BGE - Maryland (b) May 15, 2020 (amended September 11, 2020) Electric 137 81 9.50 % December 16, 2020 January 1, 2021 Natural Gas 91 21 9.65 % __________ (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 in 2021, 2022, and 2023, respectively, and natural gas revenue requirement increases of $53 million, $11 million, and $10 million in 2021, 2022, and 2023, respectively. However, the MDPSC utilized certain tax benefits to fully offset the increases in 2021 so 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 revenue requirement increases in 2022 and 2023 and BGE cannot predict the outcome. 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 March 30, 2021 Electric 246 10.95 % Fourth quarter of 2021 PECO - Pennsylvania September 30, 2020 Natural Gas 69 10.95 % Second quarter of 2021 Pepco - District of Columbia (b) May 30, 2019 (amended June 1, 2020) Electric 136 9.7 % Second quarter of 2021 Pepco - Maryland (c) October 26, 2020 (amended March 31, 2021) Electric 104 10.2 % Second quarter of 2021 DPL - Delaware (d) March 6, 2020 (amended February 2, 2021) Electric 23 10.3 % Third quarter of 2021 ACE - New Jersey (e) December 9, 2020 (amended February 26, 2021) Electric 67 10.3 % Fourth quarter of 2021 __________ (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) Pepco filed the multi-year plan enhanced proposal as an alternative to address the impacts of COVID-19. Reflects a three-year cumulative multi-year plan for 2020 through 2022 and requested revenue requirement increases of $73 million in 2022 and $63 million in 2023, to recover capital investments made during 2018 through 2020 and planned capital investments through the end of 2022. (c) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024 and total requested revenue requirement increases of $52 million effective April 1, 2023 and $52 million effective April 1, 2024 to recover capital investments made in 2019 and 2020 and planned capital investments through March 31, 2024. (d) The rates went into effect on October 6, 2020, subject to refund. (e) Requested increases are before New Jersey sales and use tax. ACE intends to put rates into effect on September 8, 2021 subject to refund. Transmission Formula Rates For 2021, the following total increases were included in ComEd’s electric transmission formula rate update. PECO, BGE, Pepco, DPL, and ACE intend to file by the required deadline for the annual update. Registrant (a) Initial Revenue Requirement Increase Annual Reconciliation Increase Total Revenue Requirement Increase Allowed Return on Rate Base (b) Allowed ROE (c) ComEd $ 33 $ 12 $ 45 8.20 % 11.50 % (a) Rates are effective June 30, 2021 - May 31, 2022, subject to review by interested parties pursuant to review protocols of ComEd's tariff. (b) Represents the weighted average debt and equity return on transmission rate bases. (c) As part of the FERC-approved settlements of ComEd’s 2007 rate case, the rate of return on common equity is 11.50%, 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%. 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 $106 million primarily due to an increase of $55 million in the Electric Distribution Formula Rate Annual Reconciliations regulatory asset, and $38 million in the Energy Efficiency Costs regulatory asset. PECO. Regulatory assets increased $56 million primarily due to an increase of $48 million in the Deferred Income Taxes regulatory asset and $9 million in the Vacation Accrual regulatory asset. BGE . Regulatory liabilities decreased $82 million primarily due to a decrease of $93 million in the Deferred Income Taxes regulatory liability, partially offset by an increase of $9 million in the Electric Energy and Natural Gas 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 March 31, 2021 $ 49 $ — $ — $ 43 $ 6 $ 3 $ 3 $ — 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 first quarter of 2021 arising from these market and weather conditions was a reduction of approximately $880 million. 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 final settlement data, 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 32 hours between February 18 and February 19 after firm load shedding ceased and to cap ancillary services at $9,000 per MWh. Appeals of certain of the PUCT’s orders also have been filed in state court. On April 19, 2021, Generation filed a declaratory action and appeal in state court challenging the PUCT’s orders setting prices at $9,000 per MWh. 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, resulting in approximately a $2.9 billion payment shortfall in collections, which is allocated to the remaining ERCOT market participants. Generation recorded its portion of this obligation of approximately $28 million on a discounted basis in the first quarter of 2021, which is to be paid over a term of 96 years. Current ERCOT rules limit recovery of default from market participants to $2.5 million per month market-wide. In February 2021, the PUCT gave ERCOT discretion to disregard its current rules, but ERCOT has declined to exercise that discretion thus far. Generation's request for rehearing of this PUCT order was denied on April 17, 2021 and an appeal is pending in state court. Additionally, several pending legislative proposals were introduced in the Texas legislature during February and March 2021 concerning the amount, timing and allocation of recovery of the $2.9 billion shortfall. Exelon and Generation are monitoring the proposed legislation and cannot predict the outcome or the financial statement impact. In addition, several other legislative proposals have been introduced in the Texas legislature during February and March 2021 addressing cold-weather preparation for power plants and natural gas production and transportation infrastructure. The proposed legislation provides the PUCT and the Railroad Commission of Texas with the option of imposing fines if the new proposed standards are not met. Exelon and Generation are monitoring the proposed legislation and cannot predict the outcome. However, such proposed legislation could have a material adverse impact in Exelon’s and Generation’s consolidated financial statements. In February 2021, more than 70 local distribution companies (LDCs) in multiple states throughout the mid-continent region, where Generation serves natural gas transportation customers, issued operational flow orders (OFOs), curtailments or other limitations on natural gas use to preserve adequate pressure on the system. When in effect, gas use above these limitations is severely penalized according to the LDCs’ tariff. Gas 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 are either voluntarily waiving or seeking regulatory approvals to waive the penalties associated with these restrictions. During March 2021, three natural gas pipelines filed individual petitions with the FERC requesting approval to waive these penalties. Generation also filed motions in March 2021 to intervene with the FERC in support of these requests from the pipelines. On March 25, 2021, the FERC issued an order on one of the petitions approving the request to waive the penalties for February 15, 2021. On April 23, 2021, Generation and several other entities filed a request for rehearing and a complaint to expand the order to include additional days of the weather events in February, from February 15 through February 19, 2021. On April 9, 2021 and April 19, 2021, the FERC issued orders on the remaining petitions approving the requests to waive the penalties. Exelon and Generation cannot predict the outcome of the FERC proceeding or the determinations made by the LDCs. New Jersey Regulatory Matters New Jersey Clean Energy Legislation. On May 23, 2018, New Jersey enacted legislation that established a ZEC program that provides compensation for nuclear plants that demonstrate to the NJBPU that they meet certain requirements, including that they make a significant contribution to air quality in the state and that their revenues are insufficient to cover their costs and risks. Under the legislation, the NJBPU will issue ZECs to qualifying nuclear power plants and the electric distribution utilities in New Jersey, including ACE, will be required to purchase those ZECs. On April 18, 2019, the NJBPU approved the award of ZECs to Salem 1 and Salem 2. Upon approval, Generation began recognizing revenue for the sale of New Jersey ZECs in the month they are generated. On March 19, 2021, a three-judge panel of the Superior Court of New Jersey Appellate Division unanimously affirmed the NJBPU’s April 2019 order awarding ZECs for the first eligibility period. On April 8, 2021, New Jersey Rate Counsel filed a notice of appeal of the Superior Court’s order to the New Jersey Supreme Court. Exelon and Generation cannot predict the outcome of the appeal. On October 1, 2020, PSEG and Generation filed applications seeking ZECs for the second eligibility period (June 2022 through May 2025). On April 27, 2021, the NJBPU approved the award of ZECs to Salem 1 and Salem 2 for the second eligibility period. See Note 7 — Early Plant Retirements for additional information related to Salem. New England Regulatory Matters Mystic Units 8 & 9 and Everett Marine Terminal Cost of Service Agreement (Exelon and Generation). On March 29, 2018, Generation notified grid operator ISO-NE of its plans to early retire Mystic Units 8 and 9 absent regulatory reforms on June 1, 2022. On May 16, 2018, Generation made a filing with FERC to establish cost-of-service compensation and terms and conditions of service for Mystic Units 8 & 9 for the period between June 1, 2022 - May 31, 2024. On December 20, 2018, FERC issued an order accepting the cost of service compensation, reflecting a number of adjustments to the annual fixed revenue requirement and allowing for recovery of a substantial portion of the costs associated with the adjacent Everett Marine Terminal acquired by Generation in October 2018. Those adjustments were reflected in a compliance filing made on March 1, 2019. In the December 20, 2018 order, FERC also directed a paper hearing on ROE using a new methodology. On January 22, 2019, Exelon and several other parties filed requests for rehearing of certain findings in the order. On July 17, 2020, FERC issued three orders, which together affirmed the recovery of key elements of Mystic's cost of service compensation, including recovery of costs associated with the operation of the Everett Marine Terminal. FERC directed a downward adjustment to the rate base for Mystic Units 8 and 9, the effect of which will be partially offset by elimination of a crediting mechanism for third party gas sales during the term of the cost of service agreement. In addition, several parties filed protests to a compliance filing by Generation on September 15, 2020, taking issue with how gross plant in-service was calculated, and Generation filed an answer to the protests on October 21, 2020. On December 21, 2020, FERC issued an order on rehearing of the three July 17, 2020 orders, clarifying several cost of service provisions. Several parties appealed the December 21, 2020 order to the U.S. Court of Appeals for the D.C. Circuit and that appeal was consolidated with appeals of orders issued December 20, 2018 and July 17, 2020 in the Mystic proceeding. The briefing schedule for the consolidated appeal has not yet been set. On February 25, 2021, Mystic made its filing to comply with the December 21, 2020 order. On April 26, 2021, FERC rejected Mystic’s language and directed another compliance filing relating to the claw back provision language, which only applies if Mystic 8 and 9 were to continue operation after the conclusion of the cost-of-service period. FERC’s April 26, 2021 order also accepted in part and rejected in part Mystic’s September 15, 2020 compliance filing. It directed a further compliance filing in 60 days consistent with the information provided in Mystic’s October 21, 2020 answer to protests. On August 25, 2020, a group of New England generators filed a complaint against Generation seeking to extend the scope of the claw back provision in the cost-of-service agreement, whereby Generation would refund certain amounts recovered during the term of the cost of service if it returns to market afterwards. On April 15, 2021 FERC dismissed the complaint. On February 16, 2021, Generation filed an unopposed motion to voluntarily dismiss an appeal filed with the U.S. Court of Appeals for the D.C. Circuit stemming from a June 2020 complaint filed with the FERC against ISO-NE over failures to follow its tariff in evaluating Mystic for transmission security for the 2024 to 2025 Capacity Commitment Period, which was granted on February 18, 2021. See Note 7 — Early Plant Retirements for additional information on the impacts of Generation’s August 2020 decision to retire Mystic Units 8 & 9 upon expiration of the cost of service agreement. Federal Regulatory Matters Operating License Renewals Conowingo Hydroelectric Project. On August 29, 2012, Generation submitted a hydroelectric license application to FERC for a new license for the Conowingo Hydroelectric Project (Conowingo). In connection with Generation’s efforts to obtain a water quality certification pursuant to Section 401 of the Clean Water Act (401 Certification) from MDE for Conowingo, Generation had been working with MDE and other stakeholders to resolve water quality licensing issues, including: (1) water quality, (2) fish habitat, and (3) sediment. On April 27, 2018, MDE issued its 401 Certification for Conowingo. On October 29, 2019, Generation and MDE filed with FERC a Joint Offer of Settlement (Offer of Settlement) that would resolve all outstanding issues relating to the 401 Certification. Pursuant to the Offer of Settlement, the parties submitted Proposed License Articles to FERC to be incorporated by FERC into the new license in accordance with FERC’s discretionary authority under the Federal Power Act.

Revenue from Contracts with Cus

Revenue from Contracts with Customers (All Registrants)	3 Months Ended
Revenue from Contracts with Customers (All Registrants)	Mar. 31, 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 within Other current assets and Customer accounts receivable, net, respectively, within 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 months ended March 31, 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 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 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 within Other current liabilities and Other noncurrent liabilities within 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 months ended March 31, 2021 and 2020. As of March 31, 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 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 $ — $ — $ — $ — The following table reflects revenues recognized in the three months ended March 31, 2021 and 2020, which were included in contract liabilities at December 31, 2020 and 2019, respectively: Three Months Ended March 31, 2021 2020 Exelon $ 17 $ 9 Generation 39 19 PHI 2 — Pepco 2 — 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 March 31, 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 $ 233 $ 100 $ 56 $ 41 $ 330 $ 760 Generation 286 131 56 35 243 751 PHI 7 8 8 6 87 116 Pepco 5 6 6 5 70 92 DPL 1 1 1 — 9 12 ACE 1 1 1 1 8 12 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)	3 Months Ended
Segment Information (All Registrants)	Mar. 31, 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 California ISO. • 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 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 months ended March 31, 2021 and 2020 is as follows: Three Months Ended March 31, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 4,187 $ — $ — $ — $ — $ — $ (293) $ 3,894 Competitive businesses natural gas revenues 1,326 — — — — — 1,326 Competitive businesses other revenues 46 — — — — — (1) 45 Rate-regulated electric revenues — 1,535 661 632 1,170 — (10) 3,988 Rate-regulated natural gas revenues — — 228 342 71 — (4) 637 Shared service and other revenues — — — — 3 491 (494) — Total operating revenues $ 5,559 $ 1,535 $ 889 $ 974 $ 1,244 $ 491 $ (802) $ 9,890 2020 Competitive businesses electric revenues $ 3,752 $ — $ — $ — $ — $ — $ (326) $ 3,426 Competitive businesses natural gas revenues 672 — — — — — (3) 669 Competitive businesses other revenues 309 — — — — — (1) 308 Rate-regulated electric revenues — 1,439 604 613 1,104 — (12) 3,748 Rate-regulated natural gas revenues — — 209 324 64 — (2) 595 Shared service and other revenues — — — — 3 480 (482) 1 Total operating revenues $ 4,733 $ 1,439 $ 813 $ 937 $ 1,171 $ 480 $ (826) $ 8,747 Intersegment revenues (c) : 2021 $ 295 $ 6 $ 2 $ 6 $ 3 $ 487 $ (799) $ — 2020 330 5 2 6 3 479 (824) 1 Depreciation and amortization: Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon 2021 $ 940 $ 292 $ 86 $ 152 $ 210 $ 17 $ — $ 1,697 2020 304 273 86 143 194 21 — 1,021 Operating expenses: 2021 $ 6,672 $ 1,210 $ 679 $ 752 $ 1,058 $ 492 $ (781) $ 10,082 2020 4,400 1,151 625 688 1,000 481 (816) 7,529 Interest expense, net: 2021 $ 72 $ 96 $ 38 $ 34 $ 67 $ 79 $ — $ 386 2020 109 94 36 32 67 72 — 410 Income (loss) before income taxes: 2021 $ (947) $ 236 $ 177 $ 196 $ 136 $ (80) $ — $ (282) 2020 (547) 204 155 222 119 (69) 1 85 Income Taxes: 2021 $ (179) $ 39 $ 10 $ (13) $ 8 $ 116 $ — $ (19) 2020 (389) 36 15 41 11 (8) — (294) Net income (loss): 2021 $ (769) $ 197 $ 167 $ 209 $ 128 $ (196) $ — $ (264) 2020 (161) 168 140 181 108 (61) 1 376 Capital Expenditures: 2021 $ 382 $ 613 $ 295 $ 336 $ 456 $ 58 $ — $ 2,140 2020 558 506 259 283 376 34 — 2,016 Total assets: March 31, 2021 $ 47,326 $ 34,825 $ 12,937 $ 11,759 $ 24,387 $ 8,788 $ (10,022) $ 130,000 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 17 — 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 18 — 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 $ 553 $ 311 $ 310 $ — $ (4) $ 1,170 Rate-regulated natural gas revenues — 71 — — — 71 Shared service and other revenues — — — 95 (92) 3 Total operating revenues $ 553 $ 382 $ 310 $ 95 $ (96) $ 1,244 2020 Rate-regulated electric revenues $ 544 $ 286 $ 276 $ — $ (2) $ 1,104 Rate-regulated natural gas revenues — 64 — — — 64 Shared service and other revenues — — — 93 (90) 3 Total operating revenues $ 544 $ 350 $ 276 $ 93 $ (92) $ 1,171 Intersegment revenues (c) : 2021 $ 1 $ 2 $ 1 $ 95 $ (96) $ 3 2020 1 2 1 92 (93) 3 Depreciation and amortization: 2021 $ 102 $ 53 $ 47 $ 8 $ — $ 210 2020 95 48 43 9 (1) 194 Operating expenses: 2021 $ 466 $ 309 $ 282 $ 97 $ (96) $ 1,058 2020 462 284 251 93 (90) 1,000 Interest expense, net: 2021 $ 34 $ 15 $ 15 $ 3 $ — $ 67 2020 34 16 15 3 (1) 67 Income (loss) before income taxes: 2021 $ 65 $ 61 $ 14 $ (4) $ — $ 136 2020 (d) 57 52 14 (4) — 119 Income Taxes: 2021 $ 6 $ 5 $ — $ (3) $ — $ 8 2020 5 7 1 (2) — 11 Net income (loss): 2021 $ 59 $ 56 $ 14 $ (1) $ — $ 128 2020 52 45 13 (2) — 108 Capital Expenditures: 2021 $ 220 $ 112 $ 123 $ 1 $ — $ 456 2020 180 95 101 — — 376 Total assets: March 31, 2021 $ 9,493 $ 5,232 $ 4,679 $ 5,020 $ (37) $ 24,387 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 17 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes in Other and Intersegment Eliminations have been adjusted by an offsetting $110 million in 2020. 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 March 31, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,174 $ (14) $ 1,160 $ 5 $ 1,165 Midwest 1,009 (11) 998 — 998 New York 382 (45) 337 — 337 ERCOT 353 (101) 252 5 257 Other Power Regions 1,172 268 1,440 (10) 1,430 Total Competitive Businesses Electric Revenues 4,090 97 4,187 — 4,187 Competitive Businesses Natural Gas Revenues 864 462 1,326 — 1,326 Competitive Businesses Other Revenues (c) 89 (43) 46 — 46 Total Generation Consolidated Operating Revenues $ 5,043 $ 516 $ 5,559 $ — $ 5,559 Three Months Ended March 31, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,264 $ (96) $ 1,168 $ 6 $ 1,174 Midwest 944 64 1,008 (6) 1,002 New York 335 (21) 314 — 314 ERCOT 155 28 183 7 190 Other Power Regions 1,007 72 1,079 (7) 1,072 Total Competitive Businesses Electric Revenues 3,705 47 3,752 — 3,752 Competitive Businesses Natural Gas Revenues 503 169 672 — 672 Competitive Businesses Other Revenues (c) 99 210 309 — 309 Total Generation Consolidated Operating Revenues $ 4,307 $ 426 $ 4,733 $ — $ 4,733 __________ (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 $84 million and gains of $179 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 562 $ 5 $ 567 $ 559 $ 8 $ 567 Midwest 702 — 702 732 (5) 727 New York 240 2 242 189 4 193 ERCOT (1,036) (148) (1,184) 76 4 80 Other Power Regions 250 (33) 217 177 (19) 158 Total Revenues net of purchased power and fuel expense for Reportable Segments 718 (174) 544 1,733 (8) 1,725 Other (b) 231 174 405 296 8 304 Total Generation Revenues net of purchased power and fuel expense $ 949 $ — $ 949 $ 2,029 $ — $ 2,029 __________ (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 $175 million and gains of $132 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 $54 million in 2021; and • the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended March 31, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 741 $ 433 $ 362 $ 605 $ 253 $ 190 $ 162 Small commercial & industrial 367 100 69 118 33 46 39 Large commercial & industrial 134 57 105 248 184 21 43 Public authorities & electric railroads 11 9 7 13 6 4 3 Other (a) 220 52 77 143 51 41 52 Total rate-regulated electric revenues (b) $ 1,473 $ 651 $ 620 $ 1,127 $ 527 $ 302 $ 299 Rate-regulated natural gas revenues Residential $ — $ 160 $ 216 $ 46 $ — $ 46 $ — Small commercial & industrial — 59 35 18 — 18 — Large commercial & industrial — — 54 2 — 2 — Transportation — 7 — 4 — 4 — Other (c) — 2 31 1 — 1 — Total rate-regulated natural gas revenues (d) $ — $ 228 $ 336 $ 71 $ — $ 71 $ — Total rate-regulated revenues from contracts with customers $ 1,473 $ 879 $ 956 $ 1,198 $ 527 $ 373 $ 299 Other revenues Revenues from alternative revenue programs $ 54 $ 10 $ 18 $ 46 $ 26 $ 9 $ 11 Other rate-regulated electric revenues (e) 8 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ 62 $ 10 $ 18 $ 46 $ 26 $ 9 $ 11 Total rate-regulated revenues for reportable segments $ 1,535 $ 889 $ 974 $ 1,244 $ 553 $ 382 $ 310 Three Months Ended March 31, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 701 $ 382 $ 339 $ 534 $ 236 $ 161 $ 137 Small commercial & industrial 362 99 67 115 35 43 37 Large commercial & industrial 134 53 103 253 188 23 42 Public authorities & electric railroads 13 7 7 15 9 3 3 Other (a) 211 58 79 169 60 54 55 Total rate-regulated electric revenues (b) $ 1,421 $ 599 $ 595 $ 1,086 $ 528 $ 284 $ 274 Rate-regulated natural gas revenues Residential $ — $ 150 $ 206 $ 40 $ — $ 40 $ — Small commercial & industrial — 51 34 17 — 17 — Large commercial & industrial — — 51 1 — 1 — Transportation — 6 — 4 — 4 — Other (c) — 1 9 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 208 $ 300 $ 64 $ — $ 64 $ — Total rate-regulated revenues from contracts with customers $ 1,421 $ 807 $ 895 $ 1,150 $ 528 $ 348 $ 274 Other revenues Revenues from alternative revenue programs $ 12 $ 2 $ 36 $ 18 $ 15 $ 1 $ 1 Other rate-regulated electric revenues (e) 6 3 3 3 1 1 1 Other rate-regulated natural gas revenues (e) — 1 3 — — — — Total other revenues $ 18 $ 6 $ 42 $ 21 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,439 $ 813 $ 937 $ 1,171 $ 544 $ 350 $ 276 __________ (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: • $6 million, $5 million at ComEd • $1 million, $2 million at PECO • $2 million, $6 million at BGE • $3 million, $3 million at PHI • $1 million, $1 million at Pepco • $2 million, $2 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 for both 2021 and 2020 • $4 million, $3 million at BGE (e) Includes late payment charge revenues.

Accounts Receivable (All Regist

Accounts Receivable (All Registrants)	3 Months Ended
Accounts Receivable (All Registrants)	Mar. 31, 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 March 31, 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 (a) 104 34 21 20 9 20 11 6 3 Less: Write-offs, net of recoveries (b) 28 1 15 6 1 5 2 3 — Balance as of March 31, 2021 $ 442 $ 65 $ 103 $ 130 $ 43 $ 101 $ 41 $ 25 $ 35 Three Months Ended March 31, 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 55 4 18 18 8 7 3 2 2 Less: Write-offs, net of recoveries (b) 20 3 6 7 2 2 1 — 1 Balance as of March 31, 2020 $ 278 $ 81 $ 71 $ 66 $ 18 $ 42 $ 15 $ 13 $ 14 _________ (a) For Generation, primarily relates to the impacts of the February 2021 extreme cold weather event. See Note 3 — Regulatory Matters for additional information. For the Utility Registrants, the increase is primarily as a result of increased receivable balances due to the colder weather and the increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnection of service to customers previously disconnected due to COVID-19. (b) Recoveries were not material to the Registrants. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended March 31, 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 10 — 1 4 1 4 2 1 1 Less: Write-offs, net of recoveries (a) 2 — — 1 1 — — — — Balance as of March 31, 2021 $ 79 $ — $ 22 $ 11 $ 9 $ 37 $ 15 $ 10 $ 12 Three Months Ended March 31, 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 8 — 3 1 2 2 1 — 1 Less: Write-offs, net of recoveries (a) 4 — 1 1 2 — — — — Balance as of March 31, 2020 $ 52 $ — $ 22 $ 7 $ 5 $ 18 $ 8 $ 4 $ 6 _________ (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 March 31, 2021 and December 31, 2020. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2021 $ 1,178 $ 671 $ 161 $ 102 $ 126 $ 118 $ 58 $ 38 $ 22 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 of $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. T he 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. Under 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 on Exelon’s and Generation’s Consolidated Balance Sheets. On April 8, 2020, Generation derecognized and transferred approximately $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 DPP. On February 17, 2021, Generation received additional cash of $250 million from the Purchasers for the remaining available funding in the Facility. On March 31, 2021, Generation received cash of approximately $150 million from the Purchasers in connection with the increased funding limit at the time of the Facility renewal. The following table summarizes the impact of the sale of certain receivables: March 31, 2021 December 31, 2020 Derecognized receivables transferred at fair value $ 1,301 $ 1,139 Cash proceeds received 900 500 DPP 401 639 Three Months Ended March 31, 2021 Loss on sale of receivables (a) $ 17 _________ (a) Reflected in Operating and maintenance expense on Exelon's and Generation's Consolidated Statement of Operations and Comprehensive Income. Three Months Ended March 31, 2021 Proceeds from new transfers (a) $ 1,036 Cash collections received on DPP and reinvested in the Facility (b) 1,174 Cash collections reinvested in the Facility 2,210 _________ (a) Customer accounts receivable sold into the Facility were $2,375 million for the three months ended March 31, 2021. (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 Statement of Cash Flows. The collection and reinvestment of DPP is recognized in Net cash provided by investing activities of the Consolidated Statement of Cash Flows. See Note 13 — Fair Value of Financial Assets and Liabilities and Note 16 — 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, 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. Three Months Ended March 31, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 1,011 $ — $ 266 $ 290 $ 199 $ 268 $ 166 $ 56 $ 46 Total receivables sold 69 81 — — — — — — — Related party transactions: Receivables purchased from Generation — — — — 12 — — — — Receivables sold to the Utility Registrants — 12 — — — — — — — Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 781 $ — $ 280 $ 284 $ 195 $ 264 $ 165 $ 53 $ 46 Total receivables sold 507 749 — — — — — — — Related party transactions: Receivables purchased from Generation — — 34 67 69 72 51 13 8 Receivables sold to the Utility Registrants — 242 — — — — — — —

Early Plant Retirements (Exelon

Early Plant Retirements (Exelon and Generation)	3 Months Ended
Early Plant Retirements (Exelon and Generation)	Mar. 31, 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 In 2015 and 2016, Generation identified the Clinton and Quad Cities nuclear plants in Illinois, Ginna and Nine Mile Point nuclear plants in New York, and TMI nuclear plant in Pennsylvania as having the greatest risk of early retirement based on economic valuation and other factors. In 2017, PSEG made public similar financial challenges facing its New Jersey nuclear plants, including Salem, of which Generation owns a 42.59% ownership interest. PSEG is the operator of Salem and also has the decision-making authority to retire Salem. Assuming the continued effectiveness of the Illinois ZES, New Jersey ZEC program, and the New York CES, Generation and CENG, through its ownership of Ginna and Nine Mile Point, no longer consider Clinton, Quad Cities, Salem, Ginna, or Nine Mile Point to be at heightened risk for early retirement. However, to the extent the Illinois ZES, New Jersey ZEC program, or the New York CES do not operate as expected over their full terms, each of these plants, in addition to FitzPatrick, would be at heightened risk for early retirement, which could have a material impact on Exelon’s and Generation’s future financial statements. In addition, FERC’s December 19, 2019 order on the MOPR in PJM may undermine the continued effectiveness of the Illinois ZES and the New Jersey ZEC program unless Illinois and New Jersey implement an FRR mechanism under which the Generation plants in these states would be removed from PJM’s capacity auction. 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, New York CES, and FERC's December 19, 2019 order on the MOPR in PJM. Generation’s Dresden, Byron, and Braidwood nuclear plants in Illinois are also showing increased signs of economic distress, in a market that does not currently compensate them for their unique contribution to grid resiliency and their ability to produce large amounts of energy without carbon and air pollution. The May 2018 PJM capacity auction for the 2021-2022 planning year resulted in the largest volume of nuclear capacity ever not selected in the auction, including all of Dresden, and portions of Byron and Braidwood. While all of LaSalle's capacity did clear in the 2021-2022 planning year auction, Generation has become increasingly concerned about the economic viability of this plant as well in a landscape where energy market prices remain depressed and energy market rules remain fatally flawed. On August 27, 2020, Generation announced that it intends to permanently cease generation operations at Byron in September 2021 and at Dresden in November 2021. The current NRC licenses for Byron Units 1 and 2 expire in 2044 and 2046, respectively, and the licenses for Dresden Units 2 and 3 expire in 2029 and 2031, respectively. 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 further discussed below, and construction work-in-progress impairments, among other items. In addition, as a result of the decisions to early retire Byron and Dresden, there are 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. The total impact for the three months ended March 31, 2021 on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income is summarized in the table below. Income statement expense (pre-tax) Three Months Ended March 31, 2021 (a) Depreciation and amortization Accelerated depreciation (a) $ 620 Accelerated nuclear fuel amortization 54 Operating and maintenance Other charges 2 Contractual offset (b) (226) Total $ 450 _________ (a) Includes the accelerated depreciation of plant assets including any ARC. (b) Reflects contractual offset for ARO accretion and ARC depreciation. Based on the regulatory agreement with the ICC, decommissioning-related activities in the first quarter of 2021 have been offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset in 2021 resulted in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 10 - Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information. Severance benefit costs will be provided to employees impacted by the early retirements of Byron and Dresden, to the extent they are not redeployed to other nuclear plants. In 2020, Exelon and Generation recorded estimated severance expense of $81 million within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. The severance liability was $81 million as of March 31, 2021 on Exelon's and Generation's Consolidated Balance Sheets. The final amount of severance benefit costs will depend on the specific employees severed. The following table provides the balance sheet amounts as of March 31, 2021 for Exelon's and Generation's significant assets and liabilities associated with the Braidwood and LaSalle nuclear plants. Current depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Braidwood LaSalle Total Asset Balances Materials and supplies inventory, net $ 83 $ 103 $ 186 Nuclear fuel inventory, net 165 264 429 Completed plant, net 1,379 1,566 2,945 Construction work in progress 33 70 103 Liability Balances Asset retirement obligation (577) (964) (1,541) NRC License First Renewal Term 2046 (Unit 1) 2042 (Unit 1) 2047 (Unit 2) 2043 (Unit 2) Exelon continues to work with stakeholders on state policy solutions, while also advocating for broader market reforms at the regional and federal level. The absence of such solutions or reforms could result in future impairments of the Midwest asset group, or accelerated depreciation for specific plants over their shortened estimated useful lives, both of which 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 the 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, 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 incremental Depreciation and amortization expense of $20 million for the three months ended March 31, 2021.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	3 Months Ended
Nuclear Decommissioning (Exelon and Generation)	Mar. 31, 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 within Property, plant, and equipment on 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 within 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 March 31, 2021: Nuclear decommissioning ARO at December 31, 2020 (a) $ 11,922 Accretion expense 124 Costs incurred related to decommissioning plants (20) Nuclear decommissioning ARO at March 31, 2021 (a) $ 12,026 _________ (a) Includes $80 million as the current portion of the ARO at March 31, 2021 and December 31, 2020, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. NDT Funds Exelon and Generation had NDT funds totaling $14,927 million and $14,599 million at March 31, 2021 and December 31, 2020, respectively. The NDT funds also include $239 million and $134 million for the current portion of the NDT funds at March 31, 2021 and December 31, 2020, respectively, which are included in Other current assets in Exelon's and Generation's Consolidated Balance Sheets. See Note 17 — Supplemental Financial Information for additional information on activities of the NDT funds. 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 stated that it intends to submit its PSDAR with additional decommissioning cost information by July 1, 2021, for Byron Units 1 and 2, and will evaluate the status of funding assurance based on the updated cost information and provide additional funding assurance by the time of shutdown if required. 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.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	3 Months Ended
Income Taxes (All Registrants)	Mar. 31, 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 March 31, 2021 Exelon (a) Generation (a) ComEd (b) PECO (b) BGE (b),(c) PHI (b) Pepco (b) DPL (b) ACE (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 14.6 4.4 6.8 (1.6) (10.1) 6.1 5.5 6.4 6.9 Qualified NDT fund income (18.4) (5.5) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference 2.4 0.6 (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences 8.8 — (0.6) (10.5) (1.4) (1.5) (2.1) (0.7) (0.9) Production tax credits and other credits 6.7 1.8 (0.2) — (0.4) (0.2) (0.2) (0.1) (0.3) Noncontrolling interests 0.6 0.2 — — — — — — — Excess deferred tax amortization 27.9 — (6.9) (3.2) (15.5) (19.3) (15.1) (18.5) (28.7) Other (d) (56.9) (3.6) (3.5) (0.1) (0.1) (0.1) 0.1 0.3 2.2 Effective income tax rate 6.7% 18.9% 16.5% 5.6% (6.6)% 5.9% 9.2% 8.2% —% Three Months Ended March 31, 2020 Exelon (b) Generation (e) ComEd (b) PECO (b) BGE (b) PHI (b) Pepco (b) DPL (b) ACE (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 34.0 0.7 8.3 0.1 5.7 5.8 4.7 6.6 6.7 Qualified NDT fund income (235.8) 36.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.5) 0.5 (0.2) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (23.0) — (1.1) (8.4) (1.2) (1.4) (2.1) (0.7) (0.8) Production tax credits and other credits (9.9) 1.3 (0.2) — (0.2) — — — — Noncontrolling interests 10.6 (1.6) — — — — — — — Excess deferred tax amortization (71.7) — (10.5) (3.0) (7.3) (15.5) (14.2) (12.7) (18.8) Tax Settlements (79.1) 12.2 — — — — — — — Other 12.5 0.6 0.3 — 0.6 (0.6) (0.6) (0.5) (0.8) Effective income tax rate (345.9)% 71.1% 17.6% 9.7% 18.5% 9.2% 8.8% 13.5% 7.1% __________ (a) Exelon and Generation recognized a loss before income taxes for the quarter ended March 31, 2021. As a result, positive percentages represent an income tax benefit for the period presented. (b) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (c) 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. (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) Generation recognized a loss before income taxes for the quarter ended March 31, 2020. As a result, positive percentages represent an income tax benefit for the period presented. Unrecognized Tax Benefits PHI and ACE have the following unrecognized tax benefits as of March 31, 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 March 31, 2021 $ 52 $ 15 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 March 31, 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.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	3 Months Ended
Retirement Benefits (All Registrants)	Mar. 31, 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 within the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three months ended March 31, 2021 and 2020. Pension Benefits OPEB Three Months Ended March 31, Three Months Ended March 31, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 110 $ 97 $ 21 $ 23 Interest cost 161 189 28 38 Expected return on assets (336) (318) (40) (41) Amortization of: Prior service cost (credit) 1 1 (8) (31) Actuarial loss 150 128 9 12 Curtailment benefits — — (1) — Net periodic benefit cost $ 86 $ 97 $ 9 $ 1 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 March 31, Pension and OPEB Costs 2021 2020 Exelon $ 95 $ 98 Generation 26 27 ComEd 32 28 PECO 2 1 BGE 15 16 PHI 12 17 Pepco 2 3 DPL 1 1 ACE 3 3 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 months ended March 31, 2021 and 2020, respectively. Three Months Ended March 31, Savings Plans Matching Contributions 2021 2020 Exelon $ 33 $ 33 Generation 13 13 ComEd 8 7 PECO 3 3 BGE 2 2 PHI 3 3 Pepco 1 1 DPL 1 1

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	3 Months Ended
Derivative Financial Instruments (All Registrants)	Mar. 31, 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 March 31, 2021 and December 31, 2020 and is not presented in the fair value tables below. The following table provides a summary of the derivative fair value balances recorded by Exelon, Generation, and ComEd as of March 31, 2021 and December 31, 2020: Exelon Generation ComEd March 31, 2021 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 569 $ 2,566 $ 28 $ 24 $ (2,049) $ 569 $ — Mark-to-market derivative assets 488 1,400 5 45 (962) 488 — Total mark-to-market derivative assets 1,057 3,966 33 69 (3,011) 1,057 — Mark-to-market derivative liabilities (418) (2,472) (13) 49 2,049 (387) (31) Mark-to-market derivative liabilities (454) (1,179) (1) 28 962 (190) (264) Total mark-to-market derivative liabilities (872) (3,651) (14) 77 3,011 (577) (295) Total mark-to-market derivative net assets (liabilities) $ 185 $ 315 $ 19 $ 146 $ — $ 480 $ (295) 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. These amounts are not material and not reflected in the table above. (b) Of the collateral posted, $148 million and $209 million represents variation margin on the exchanges as of March 31, 2021 and December 31, 2020 respectively. Economic Hedges (Commodity Price Risk) Generation. For the three months ended March 31, 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 2021 2020 Income Statement Location Gain (Loss) Operating revenues $ (83) $ 175 Purchased power and fuel 265 (47) Total Exelon and Generation $ 182 $ 128 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 March 31, 2021, the percentage of expected generation hedged for the Mid-Atlantic, Midwest, New York, and ERCOT reportable segments is 94%-97% for 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 months ended March 31, 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 $563 million and $665 million for Exelon and Generation as of March 31, 2021 and December 31, 2020, respectively. The mark-to-market derivative assets and liabilities as of March 31, 2021 and December 31, 2020 and the mark-to-market gains and losses for the three months ended March 31, 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 March 31, 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 March 31, 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 $ 431 $ 31 $ 400 — $ — Non-investment grade 43 4 39 No external ratings Internally rated — investment grade 146 1 145 Internally rated — non-investment grade 70 25 45 Total $ 690 $ 61 $ 629 — $ — Net Credit Exposure by Type of Counterparty As of March 31, 2021 Investor-owned utilities, marketers, power producers $ 451 Energy cooperatives and municipalities 123 Other 55 Total $ 629 _________ (a) As of March 31, 2021, credit collateral held from counterparties where Generation had credit exposure included $32 million of cash and $29 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 March 31, 2021, the Utility Registrants’ counterparty credit risk with suppliers was not material. 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 March 31, 2021 December 31, 2020 Gross fair value of derivative contracts containing this feature (a) $ (948) $ (834) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 518 537 Net fair value of derivative contracts containing this feature (c) $ (430) $ (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 March 31, 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. March 31, 2021 December 31, 2020 Cash collateral posted $ 232 $ 511 Letters of credit posted 242 226 Cash collateral held 101 110 Letters of credit held 41 40 Additional collateral required in the event of a credit downgrade below investment grade 1,379 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)	3 Months Ended
Debt and Credit Agreements (All Registrants)	Mar. 31, 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 March 31, 2021 and December 31, 2020. PECO had no commercial paper borrowings as of both March 31, 2021 and December 31, 2020. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer March 31, 2021 December 31, 2020 March 31, 2021 December 31, 2020 Exelon (a)(b) $ 1,628 $ 1,031 0.52 % 0.25 % Generation (b) 1,337 340 0.60 % 0.27 % ComEd 135 323 0.16 % 0.23 % BGE 156 — 0.15 % — % PHI (c) — 368 — % 0.24 % Pepco — 35 — % 0.22 % DPL — 146 — % 0.24 % ACE — 187 — % 0.25 % __________ (a) Exelon Corporate had no outstanding commercial paper borrowings as of both March 31, 2021 and December 31, 2020. (b) Higher outstanding commercial paper primarily driven by increased liquidity needs from the February 2021 extreme cold weather event. See Note 3 – Regulatory Matters for additional information. (c) Represents the consolidated amounts of Pepco, DPL, and ACE. 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 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. Long-Term Debt Issuance of Long-Term Debt During the three months ended March 31, 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 Energy Efficiency Project Financing (a) 2.53 % May 31, 2021 1 Funding to install energy conservation measures for the Fort AP Hill 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. PECO First and Refunding Mortgage Bonds 3.05 % March 15, 2051 375 Funding for general corporate purposes. Pepco (b) First Mortgage Bonds 2.32 % March 30, 2031 150 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) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt. (b) On March 30, 2021, Pepco entered into a purchase agreement of First Mortgage Bonds of $125 million at 3.29% due on September 28, 2051. The closing date of the issuance is expected to occur in September 2021. Debt Covenants As of March 31, 2021, the Registrants are in compliance with debt covenants.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	3 Months Ended
	Mar. 31, 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 March 31, 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 on their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. March 31, 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 $ 38,529 $ 39,255 $ 3,115 $ 42,370 $ 36,912 $ 40,688 $ 3,064 $ 43,752 Generation 6,060 5,497 1,158 6,655 6,087 5,648 1,208 6,856 ComEd 9,674 10,853 — 10,853 8,983 11,117 — 11,117 PECO 4,125 4,491 50 4,541 3,753 4,553 50 4,603 BGE 3,665 3,991 — 3,991 3,664 4,366 — 4,366 PHI 7,577 6,050 1,907 7,957 7,006 6,099 1,806 7,905 Pepco 3,317 3,112 823 3,935 3,165 3,336 748 4,084 DPL 1,802 1,386 524 1,910 1,677 1,484 455 1,939 ACE 1,718 1,302 560 1,862 1,413 1,018 602 1,620 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 465 $ 465 $ 390 $ — $ 467 $ 467 ComEd 205 — 243 243 205 — 246 246 PECO 184 — 222 222 184 — 221 221 SNF Obligation Exelon $ 1,208 $ 979 $ — $ 979 $ 1,208 $ 909 $ — $ 909 Generation 1,208 979 — 979 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 March 31, 2021 and December 31, 2020: Exelon and Generation Exelon Generation As of March 31, 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) $ 968 $ — $ — $ — $ 968 $ 125 $ — $ — $ — $ 125 NDT fund investments Cash equivalents (b) 509 95 — — 604 509 95 — — 604 Equities 4,439 1,574 — 1,555 7,568 4,439 1,574 — 1,555 7,568 Fixed income Corporate debt (c) — 1,023 283 — 1,306 — 1,023 283 — 1,306 U.S. Treasury and agencies 2,030 41 — — 2,071 2,030 41 — — 2,071 Foreign governments — 51 — — 51 — 51 — — 51 State and municipal debt — 40 — — 40 — 40 — — 40 Other 40 35 — 1,285 1,360 40 35 — 1,285 1,360 Fixed income subtotal 2,070 1,190 283 1,285 4,828 2,070 1,190 283 1,285 4,828 Private credit — — 196 617 813 — — 196 617 813 Private equity — — — 532 532 — — — 532 532 Real estate — — — 686 686 — — — 686 686 NDT fund investments subtotal (d)(e) 7,018 2,859 479 4,675 15,031 7,018 2,859 479 4,675 15,031 Rabbi trust investments Cash equivalents 60 — — — 60 4 — — — 4 Mutual funds 95 — — — 95 31 — — — 31 Fixed income — 10 — — 10 — — — — — Life insurance contracts — 89 35 — 124 — 29 — — 29 Rabbi trust investments subtotal 155 99 35 — 289 35 29 — — 64 Investments in equities (f) 177 — — — 177 177 — — — 177 Commodity derivative assets Economic hedges 478 1,748 1,740 — 3,966 478 1,748 1,740 — 3,966 Proprietary trading — 16 17 — 33 — 16 17 — 33 Effect of netting and allocation of collateral (g)(h) (356) (1,387) (1,199) — (2,942) (356) (1,387) (1,199) — (2,942) Commodity derivative assets subtotal 122 377 558 — 1,057 122 377 558 — 1,057 DPP consideration — 401 — — 401 — 401 — — 401 Exelon Generation As of March 31, 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 8,440 3,736 1,072 4,675 17,923 7,477 3,666 1,037 4,675 16,855 Liabilities Commodity derivative liabilities Economic hedges (359) (1,642) (1,945) — (3,946) (359) (1,642) (1,650) — (3,651) Proprietary trading — (9) (5) — (14) — (9) (5) — (14) Effect of netting and allocation of collateral (g)(h) 252 1,532 1,304 — 3,088 252 1,532 1,304 — 3,088 Commodity derivative liabilities subtotal (107) (119) (646) — (872) (107) (119) (351) — (577) Deferred compensation obligation — (146) — — (146) — (43) — — (43) Total liabilities (107) (265) (646) — (1,018) (107) (162) (351) — (620) Total net assets $ 8,333 $ 3,471 $ 426 $ 4,675 $ 16,905 $ 7,370 $ 3,504 $ 686 $ 4,675 $ 16,235 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 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 $1,273 million and $409 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $93 million and $59 million at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $52 million and $53 million at March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $608 million and $171 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $29 million and $20 million at March 31, 2021 and December 31, 2020, respectively. (b) Includes $108 million and $116 million of cash received from outstanding repurchase agreements at March 31, 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 $(58) million and $(62) million as of March 31, 2021 and December 31, 2020, respectively, held in an investment vehicle primarily to hedge the equity option component of its convertible debt. (d) Includes derivative assets of less than $1 million and $2 million, which have total notional amounts of $2,049 million and $1,043 million at March 31, 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 $104 million and $181 million at March 31, 2021 and December 31, 2020, respectively, which include certain derivative assets that have notional amounts of $158 million and $104 million at March 31, 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. Generation recorded the fair value of these investments in Other current assets on Exelon's and Generation's Consolidated Balance Sheets based on the quoted market prices of the stocks at March 31, 2021 and December 31, 2020, which resulted in unrealized gains of $95 million and $186 million within Other, net in Exelon's and Generation's Consolidated Statement of Operations and Comprehensive Income for the three months ended March 31, 2021 and for the year ended December 31, 2020, respectively. (g) Collateral (received)/posted from counterparties, net of collateral paid to counterparties, totaled $(104) million, $145 million, and $105 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of March 31, 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) Of the collateral (received)/posted, $(148) million and $209 million represents variation margin on the exchanges as of March 31, 2021 and December 31, 2020, respectively. As of March 31, 2021, Exelon and Generation have outstanding commitments to invest in private credit, private equity, and real estate investments of approximately $298 million, $239 million, and $344 million, respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation hold investments without readily determinable fair values with carrying amounts of $61 million and $50 million as of March 31, 2021, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three months ended March 31, 2021. ComEd, PECO, and BGE ComEd PECO BGE As of March 31, 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) $ 300 $ — $ — $ 300 $ 7 $ — $ — $ 7 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 9 — — 9 11 — — 11 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 11 — — 11 Total assets 300 — — 300 16 13 — 29 11 — — 11 Liabilities Deferred compensation obligation — (8) — (8) — (9) — (9) — (6) — (6) Mark-to-market derivative liabilities (b) — — (295) (295) — — — — — — — — Total liabilities — (8) (295) (303) — (9) — (9) — (6) — (6) Total net assets (liabilities) $ 300 $ (8) $ (295) $ (3) $ 16 $ 4 $ — $ 20 $ 11 $ (6) $ — $ 5 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 $59 million and $83 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $40 million and $37 million at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $43 million at both March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $48 million and $18 million at March 31, 2021 and December 31, 2020, respectively. BGE excludes cash of $21 million and $24 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $1 million at both March 31, 2021 and December 31, 2020. (b) The Level 3 balance consists of the current and noncurrent liability of $31 million and $264 million, respectively, at March 31, 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 March 31, 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) $ 527 $ — $ — $ 527 $ 86 $ — $ — $ 86 Rabbi trust investments Cash equivalents 53 — — 53 55 — — 55 Mutual funds 15 — — 15 14 — — 14 Fixed income — 10 — 10 — 11 — 11 Life insurance contracts — 26 35 61 — 26 34 60 Rabbi trust investments subtotal 68 36 35 139 69 37 34 140 Total assets 595 36 35 666 155 37 34 226 Liabilities Deferred compensation obligation — (16) — (16) — (17) — (17) Total liabilities — (16) — (16) — (17) — (17) Total net assets $ 595 $ 20 $ 35 $ 650 $ 155 $ 20 $ 34 $ 209 Pepco DPL ACE As of March 31, 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) $ 128 $ — $ — $ 128 $ 50 $ — $ — $ 50 $ 349 $ — $ — $ 349 Rabbi trust investments Cash equivalents 53 — — 53 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 35 61 — — — — — — — — Rabbi trust investments subtotal 53 28 35 116 — — — — — — — — Total assets 181 28 35 244 50 — — 50 349 — — 349 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 181 $ 26 $ 35 $ 242 $ 50 $ — $ — $ 50 $ 349 $ — $ — $ 349 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 $72 million and $74 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $34 million and $30 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at March 31, 2021 and December 31, 2020, respectively. DPL excludes cash of $14 million and $15 million at March 31, 2021 and December 31, 2020, respectively. ACE excludes cash of $17 million at both March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at March 31, 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 months ended March 31, 2021 and 2020: Exelon Generation ComEd PHI and Pepco Three months ended March 31, 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 (276) 1 (278) (a) (277) — 1 — Included in noncurrent payables to affiliates — 1 — 1 — — (1) Included in regulatory assets 7 — — — 6 (b) — 1 Change in collateral (57) — (57) (57) — — — Purchases, sales, issuances and settlements Purchases 109 — 109 109 — — — Sales 1 — 1 1 — — — Settlements (20) (20) — (20) — — — Transfers out of Level 3 2 — 2 (c) 2 — — — Balance as of March 31, 2021 $ 426 $ 479 $ 207 $ 686 $ (295) $ 35 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2021 $ (147) $ 1 $ (149) $ (148) $ — $ 1 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 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 10 (1) 10 (a) 9 — 1 — Included in noncurrent payables to affiliates — (1) — (1) — — 1 Included in regulatory assets (14) — — — (13) (b) — (1) Change in collateral 1 — 1 1 — — — Purchases, sales, issuances and settlements Purchases 42 3 39 42 — — — Sales (22) — (22) (22) — — — Settlements (14) (14) — (14) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 15 — 15 (c) 15 — — — Balance as of March 31, 2020 $ 1,088 $ 498 $ 862 $ 1,360 $ (314) $ 42 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2020 $ 187 $ (1) $ 187 $ 186 $ — $ 1 $ — __________ (a) Includes a reduction for the reclassification of $129 million and $177 million of realized losses due to the settlement of derivative contracts for the three months ended March 31, 2021 and 2020 respectively. (b) Includes $2 million of decreases in fair value and an increase for realized losses due to settlements of $8 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2021. Includes $23 million of decrease in fair value and an increase for realized losses due to settlements of $10 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 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 months ended March 31, 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 for the three months ended March 31, 2021 $ (116) $ (162) $ 1 $ 1 $ (116) $ (162) $ 1 $ 1 Total unrealized (losses) gains for the three months ended March 31, 2021 (65) (84) 1 1 (65) (84) 1 1 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total gains (losses) for the three months ended March 31, 2020 $ 72 $ (62) $ 1 $ (1) $ 72 $ (62) $ (1) $ 1 Total unrealized gains (losses) gains for the three months ended March 31, 2020 205 (18) 1 (1) 205 (18) (1) 1 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 March 31, 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) $ 90 $ 245 Discounted Forward power $1.35 - $235 $32 $2.25 - $163 $30 Forward gas $1.42 - $8.18 $2.59 $1.57 - $7.88 $2.59 Option Volatility 11% - 116% 27% 11% - 237% 32% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 12 $ 23 Discounted Forward power $9 - $102 $30 $10 - $106 $27 Mark-to-market derivatives (Exelon and ComEd) $ (295) $ (301) Discounted Forward heat (c) 8x - 9x 8.85x 8x - 9x 8.85x Marketability 3% - 8% 4.93% 3% - 8% 4.93% Renewable 90% - 123% 99% 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 posted on level three positions of $105 million and $162 million as of March 31, 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 (

Commitments and Contingencies (All Registrants)	3 Months Ended
Commitments and Contingencies (All Registrants)	Mar. 31, 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 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 March 31, 2021: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 79 64 53 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 March 31, 2021, 27 MWs of new generation were developed and Exelon and Generation have incurred costs of $121 million. 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 March 31, 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 $ 1,639 $ 1,156 $ 483 $ — $ — $ — $ — Surety bonds (a) 1,077 919 158 — — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 29 — 3 4 6 5 11 Total commercial commitments $ 3,123 $ 2,075 $ 644 $ 4 $ 6 $ 5 $ 389 Generation Letters of credit $ 1,623 $ 1,141 $ 482 $ — $ — $ — $ — Surety bonds (a) 932 794 138 — — — — Total commercial commitments $ 2,555 $ 1,935 $ 620 $ — $ — $ — $ — ComEd Letters of credit $ 7 $ 7 $ — $ — $ — $ — $ — Surety bonds (a) 17 14 3 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 224 $ 21 $ 3 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 2 $ 2 $ — $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 180 $ 2 $ — $ — $ — $ — $ 178 BGE Letters of credit $ 3 $ 2 $ 1 $ — $ — $ — $ — Surety bonds (a) 3 3 — — — — — Total commercial commitments $ 6 $ 5 $ 1 $ — $ — $ — $ — PHI Surety bonds (a) $ 23 $ 20 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 29 — 3 4 6 5 11 Total commercial commitments $ 52 $ 20 $ 6 $ 4 $ 6 $ 5 $ 11 Pepco Surety bonds (a) $ 14 $ 14 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 10 — 1 1 2 2 4 Total commercial commitments $ 24 $ 14 $ 1 $ 1 $ 2 $ 2 $ 4 DPL Surety bonds (a) $ 5 $ 2 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 12 — 1 2 3 2 4 Total commercial commitments $ 17 $ 2 $ 4 $ 2 $ 3 $ 2 $ 4 ACE Surety bonds (a) $ 4 $ 4 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 11 $ 4 $ 1 $ 1 $ 1 $ 1 $ 3 __________ (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 $73 million guaranteed by Exelon and PHI, of which $25 million, $30 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 2026. • PECO has 8 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 ex pected 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 March 31, 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 within their respective Consolidated Balance Sheets: March 31, 2021 December 31, 2020 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 473 $ 306 $ 483 $ 314 Generation 119 — 121 — ComEd 281 280 293 293 PECO 23 21 23 21 BGE 6 5 2 — PHI 44 — 44 — Pepco 42 — 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 by early 2022. 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 $280 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 on 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 on 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 $30 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 on 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 August 31, 2021 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 the National Park Service 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. 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 March 31, 2021 and December 31, 2020, Exelon and Generation had recorded estimated liabilities of approximately $88 million and $89 million, respectively, in total for asbestos-related bodily injury claims. As of March 31, 2021, approximately $24 million of this amount related to 243 open claims presented to Generation, while the remaining $64 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 on 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: • 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. Defendants' responsive pleading is due June 9, 2021. • 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. These three state cases were consolidated into a single action in October of 2020. In addition, on November 2, 2020, the Citizens Utility Board (CUB) filed a motion to intervene in the state 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 CUB’s 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, to jointly engage in mediation and have informed the court. The parties will report back to the court on the status of the mediation planning on April 29, 2021. A tentative date of June 1, 2021 has been set for oral argument on the pending motion to dismiss, but the parties have agreed to extend that date so long as a date to mediate has been selected by that time. • 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, CUB filed a motion to intervene in these cases on October 22, 2020 which was granted on December 23, 2020. In addition, 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. The Potter plaintiffs decided not to move forward with their separate lawsuit at this time and 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. Briefing on that motion was completed on March 22, 2021. As noted above, on March 25, 2021, the parties agreed, along with the state court plaintiffs, to jointly engage in mediation. The parties have notified the court of their decision to mediate. Oral argument on the pending motion to dismiss and any discovery will be stayed pending mediation. • 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. 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. 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 information. Various lawsuits have been filed against Generation during March and April of 2021 related to these events, including: • On March 5, 2021, Generation, along with more than 160 power generators and transmission and distribution companies, was sued by approximately 160 individually named plaintiffs, purportedly on behalf of all Texans who allegedly suffered loss of life or sustained personal injury, property damage or other losses as a result of the weather events. The plaintiffs allege that the defendants failed to properly prepare for the cold weather and failed to properly conduct their operations, seeking compensatory as well as punitive damages. On April 26, 2021, another multi-plaintiff lawsuit was filed on behalf of approximately 90 plaintiffs against more than 300 defendants, including Generation, involving similar allegations of liability and claims of personal injury and property damage. During March and April of 2021, approximately 45 additional wrongful death lawsuits, naming multiple defendants including Generation, were filed by individual plaintiffs in different Texas counties, all arising out of the February weather events. Co-defendants in these lawsuits include ERCOT, transmission and distribution utilities and other generators. Generation disputes liability and denies that it is responsible for any of plaintiffs’ alleged claims and is vigorously contesting them. No loss contingencies have been reflected in Exelon’s and Generation’s consolidated financial statements with respect to these matters, as such contingencies are neither probable nor reasonably estimable at this time. • On March 22, 2021, a LDC filed a lawsuit in Missouri federal court against Generation for breach of contract and unjust enrichment, seeking damages of approximately $40 million. The plaintiff claims that Generation failed to deliver gas to its customers in February of 2021, causing the plaintiff to incur damages by forcing it to purchase gas for Generation’s customers and by Generation’s refusal to pay the resulting penalties. On March 26, 2021, Generation filed a complaint with the MPSC against the LDC to void the OFO penalties, or alternatively to grant a waiver or variance from the tariff requirements, to prohibit the LDC from billing or otherwise attempting to collect from Generation or any Missouri customer any portion of the penalties claimed by the LDC until the resolution of the complaint, and to prohibit the LDC from taking any retaliatory measure, including termination of service. Generation has requested expedited treatment, but there is no timeline by which the MPSC must act. Based on the penalty provisions within the tariff that was in effect at the relevant time, Exelon and Generation recorded a liability of approximately $40 million as of March 31, 2021. General (All Registrants). The Registrants are involved in various other litigation matters that are being defended and handled in the ordinary course of business. The assessment of whether a loss is probable or reasonably possible, and whether the loss or a range of loss is estimable, often involves a series of complex judgments about future events. The Registrants maintain accruals for such losses that are probable of being incurred and subject to reasonable estimation. Management is sometimes unable to estimate an amount or range of reasonably possible loss, particularly where (1) the damages sought are indeterminate, (2) the proceedings are in the early stages, or (3) the matters involve novel or unsettled legal theories. In such cases, there is considerable uncertainty regarding the timing or ultimate resolution of such matters, including a possible eventual loss.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon)	3 Months Ended
Changes in Accumulated Other Comprehensive Income (Exelon)	Mar. 31, 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 March 31, 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 — (2) 1 (1) Amounts reclassified from AOCI — 55 — 55 Net current-period OCI — 53 1 54 Ending balance $ (5) $ (3,319) $ (22) $ (3,346) Three Months Ended March 31, 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 (1) (7) (8) (16) Amounts reclassified from AOCI — 37 — 37 Net current-period OCI (1) 30 (8) 21 Ending balance $ (3) $ (3,135) $ (35) $ (3,173) _________ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 10 — 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 March 31, 2021 2020 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 1 $ 4 Actuarial loss reclassified to periodic benefit cost (19) (17) Pension and non-pension postretirement benefit plans valuation adjustment — 3

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, PHI and ACE)	3 Months Ended
	Mar. 31, 2021
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure	Variable Interest Entities (Exelon, Generation, PHI and ACE) At March 31, 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 March 31, 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. March 31, 2021 December 31, 2020 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 175 $ 175 $ — $ — $ 98 $ 98 $ — $ — Restricted cash and cash equivalents 37 33 4 4 47 44 3 3 Accounts receivable Customer 145 145 — — 148 148 — — Other 35 35 — — 36 36 — — Unamortized energy contract assets 22 22 — — 22 22 — — Inventories, net Materials and supplies 242 242 — — 244 244 — — Assets held for sale (b) — — — — 101 101 — — Other current assets 448 443 5 — 674 669 5 — Total current assets 1,104 1,095 9 4 1,370 1,362 8 3 Property, plant, and equipment, net 5,747 5,747 — — 5,803 5,803 — — Nuclear decommissioning trust funds 3,089 3,089 — — 3,007 3,007 — — Unamortized energy contract assets 243 243 — — 249 249 — — Other noncurrent assets 47 38 9 9 52 42 10 10 Total noncurrent assets 9,126 9,117 9 9 9,111 9,101 10 10 Total assets (c) $ 10,230 $ 10,212 $ 18 $ 13 $ 10,481 $ 10,463 $ 18 $ 13 Long-term debt due within one year $ 90 $ 69 $ 21 $ 16 $ 94 $ 68 $ 26 $ 21 Accounts payable 95 95 — — 81 81 — — Accrued expenses 67 67 — — 70 70 — — Unamortized energy contract liabilities 3 3 — — 4 4 — — Liabilities held for sale (b) — — — — 16 16 — — Other current liabilities 1 1 — — 5 5 — — Total current liabilities 256 235 21 16 270 244 26 21 Long-term debt 861 861 — — 889 889 — — Asset retirement obligations 2,347 2,347 — — 2,318 2,318 — — Other noncurrent liabilities 116 116 — — 129 129 — — Total noncurrent liabilities 3,324 3,324 — — 3,336 3,336 — — Total liabilities (d) $ 3,580 $ 3,559 $ 21 $ 16 $ 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) Ex elon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $22 million and $22 million, non-current unamortized energy contract assets of $222 million and $249 million, Assets held for sale of $0 million and $9 million, and other unrestricted assets of $1 million and $1 million as of March 31, 2021 and December 31, 2020, respectively (d) Exelon’s and Generation’s balances include liabilities with recourse of $2 million a nd $8 million as of March 31, 2021 and December 31, 2020, respectively. As of March 31, 2021 and December 31, 2020, Exelon's and Generation's consolidated VIEs consist of: Consolidated VIE or VIE groups: Reason entity is a VIE: Reason Generation is primary beneficiary: CENG - A joint venture between Generation and EDF. Generation has a 50.01% equity ownership in CENG. 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. EDF has the option to sell its 49.99% equity interest in CENG to Generation. 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. 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, • Generation and EDF share in the $688 million of contingent payment obligations for the payment of contingent retrospective premium adjustments for the nuclear liability insurance, and • 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. 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 March 31, 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 March 31, 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: March 31, 2021 December 31, 2020 Commercial Equity Total Commercial Equity Total Total assets (a) $ 789 $ 386 $ 1,175 $ 777 $ 401 $ 1,178 Total liabilities (a) 95 218 313 61 223 284 Exelon's ownership interest in VIE (a) — 150 150 — 157 157 Other ownership interests in VIE (a) 694 18 712 716 21 737 _________ (a) These items represent amounts on 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 March 31, 2021 and December 31, 2020. As of March 31, 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)	3 Months Ended
Supplemental Financial Information (All Registrants)	Mar. 31, 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 March 31, 2021 Operating lease income $ 4 $ 3 $ 1 $ 1 Variable lease income 64 64 — — Three Months Ended March 31, 2020 Operating lease income $ 5 $ 3 $ 1 $ 1 Variable lease income 69 69 — — Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2021 Utility taxes (a) $ 217 $ 24 $ 59 $ 35 $ 25 $ 74 $ 67 $ 6 $ 1 Property 154 68 8 4 42 32 21 10 1 Payroll 61 28 7 4 5 7 2 1 — Three Months Ended March 31, 2020 Utility taxes (a) $ 218 $ 26 $ 60 $ 31 $ 26 $ 75 $ 69 $ 6 $ — Property 150 69 7 4 39 31 21 9 1 Payroll 63 31 7 4 4 8 2 1 1 __________ (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 March 31, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 291 $ 291 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 203 203 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units (82) (82) — — — — — — — Non-Regulatory Agreement Units (66) (66) — — — — — — — Regulatory offset to NDT fund-related activities (b) (167) (167) — — — — — — — Decommissioning-related activities 179 179 — — — — — — — AFUDC — Equity 28 — 4 6 7 11 9 1 1 Non-service net periodic benefit cost 20 — — — — — — — — Three Months Ended March 31, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 47 $ 47 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 82 82 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units (932) (932) — — — — — — — Non-Regulatory Agreement Units (706) (706) — — — — — — — Regulatory offset to NDT fund-related activities (b) 709 709 — — — — — — — Decommissioning-related activities (800) (800) — — — — — — — AFUDC — Equity 23 — 6 3 5 9 6 1 2 Non-service net periodic benefit cost 10 — — — — — — — — __________ (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, including the elimination of income taxes related to all NDT fund activity for those units. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning. 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 Three Months Ended March 31, 2021 Property, plant, and equipment (a) $ 1,522 $ 928 $ 239 $ 82 $ 106 $ 154 $ 67 $ 42 $ 37 Amortization of regulatory assets (a) 160 — 53 4 46 56 35 11 10 Amortization of intangible assets, net (a) 15 12 — — — — — — — Amortization of energy contract assets and liabilities (b) 4 3 — — — — — — — Nuclear fuel (c) 276 276 — — — — — — — ARO accretion (d) 127 127 — — — — — — — Total depreciation, amortization and accretion $ 2,104 $ 1,346 $ 292 $ 86 $ 152 $ 210 $ 102 $ 53 $ 47 Three Months Ended March 31, 2020 Property, plant, and equipment (a) $ 856 $ 290 $ 228 $ 79 $ 97 $ 144 $ 64 $ 38 $ 34 Amortization of regulatory assets (a) 149 — 45 7 46 50 31 10 9 Amortization of intangible assets, net (a) 16 14 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 231 231 — — — — — — — ARO accretion (d) 124 124 — — — — — — — Total depreciation, amortization and accretion $ 1,378 $ 661 $ 273 $ 86 $ 143 $ 194 $ 95 $ 48 $ 43 __________ (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 Three Months Ended March 31, 2021 Pension and non-pension postretirement benefit costs $ 95 $ 26 $ 32 $ 2 $ 14 $ 12 $ 2 $ 1 $ 3 Allowance for credit losses 85 34 13 24 4 10 5 4 1 Other decommissioning-related activity (a) (322) (332) — — — — — — — Energy-related options (b) 17 17 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) (129) — (54) (10) (18) (46) (26) (9) (11) Long-term incentive plan 32 — — — — — — — — Amortization of operating ROU asset 37 21 — — 7 7 1 3 1 AFUDC - Equity (28) — (4) (6) (7) (11) (9) (1) (1) Three Months Ended March 31, 2020 Pension and non-pension postretirement benefit costs $ 98 $ 27 $ 28 $ 1 $ 15 $ 17 $ 3 $ 1 $ 3 Allowance for credit losses 45 4 7 17 7 10 4 3 3 Other decommissioning-related activity (a) 128 128 — — — — — — — Energy-related options (b) 6 6 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (d) (71) — (17) — (35) (19) (15) (4) — Long-term incentive plan (7) — — — — — — — — Amortization of operating ROU asset 51 35 — — 8 5 2 2 1 AFUDC - Equity (23) — (6) (3) (5) (9) (6) (1) (2) __________ (a) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income, and income taxes related to all NDT fund activity for these units. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (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, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO and ACE, reflects the change in regulatory assets and liabilities associated with their transmission formula rates. See Note 3 — Regulatory Matters for additional information. (d) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution and energy efficiency formula rates. For BGE, Pepco, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms. See Note 3 — Regulatory Matters for additional information. 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 March 31, 2021 Cash and cash equivalents $ 1,908 $ 721 $ 86 $ 48 $ 21 $ 558 $ 134 $ 64 $ 353 Restricted cash and cash equivalents 374 41 270 7 1 37 33 — 4 Restricted cash included in other long-term assets 52 — 43 — — 9 — — 9 Total cash, restricted cash, and cash equivalents $ 2,334 $ 762 $ 399 $ 55 $ 22 $ 604 $ 167 $ 64 $ 366 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 March 31, 2020 Cash and cash equivalents $ 1,457 $ 821 $ 514 $ 31 $ 11 $ 49 $ 18 $ 7 $ 8 Restricted cash and cash equivalents 414 150 211 7 1 37 33 — 3 Restricted cash included in other long-term assets 121 — 108 — — 12 — — 12 Total cash, restricted cash, and cash equivalents $ 1,992 $ 971 $ 833 $ 38 $ 12 $ 98 $ 51 $ 7 $ 23 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 March 31, 2021 Compensation-related accruals (a) $ 581 $ 210 $ 91 $ 42 $ 49 $ 73 $ 26 $ 15 $ 12 Taxes accrued 540 279 70 18 50 108 92 10 12 Interest accrued 424 76 65 36 41 79 37 20 20 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)	3 Months Ended
Related Party Transactions (All Registrants)	Mar. 31, 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 March 31, 2021 2020 Operating revenues from affiliates: ComEd (a)(b) $ 78 $ 90 PECO (c) 42 37 BGE (d) 72 99 PHI 100 103 Pepco (e) 75 79 DPL (f) 21 22 ACE (g) 4 2 Other 3 1 Total operating revenues from affiliates (Generation) $ 295 $ 330 __________ (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 months ended March 31, 2021, ComEd’s Purchased power from Generation of $84 million is recorded as Operating revenues from ComEd of $78 million and as Purchased power and fuel from ComEd of $6 million at Generation. For the three months ended March 31, 2020 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $90 million and as Purchased power and fuel from ComEd of $7 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. Operating and maintenance expense from affiliates 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 March 31, Three Months Ended March 31, 2021 2020 2021 2020 Exelon BSC $ 124 $ 113 PHISCO 17 14 Generation BSC $ 144 $ 140 10 11 ComEd BSC 71 72 45 42 PECO BSC 39 37 17 16 BGE BSC 43 41 20 28 PHI BSC 39 37 32 16 PHISCO — — 17 14 Pepco BSC 22 21 13 6 PHISCO 30 30 7 6 DPL BSC 14 13 10 5 PHISCO 25 24 5 4 ACE BSC 12 11 8 4 PHISCO 22 22 5 4 Current Receivables from/Payables to affiliates The following tables present current receivables from affiliates and current payables to affiliates: March 31, 2021 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 17 $ — $ — $ — $ — $ — $ 84 $ — $ 24 $ 125 ComEd $ 50 (a) — — — — — 49 — 5 104 PECO 15 — — — — — 24 — 7 46 BGE 11 1 — — — — 30 — 1 43 PHI — 1 — — — — — 7 — 10 18 Pepco 12 1 — — — — 16 14 1 44 DPL 2 — — — — — 11 11 — 24 ACE 8 — — — — — 8 10 1 27 Other 8 1 — — — — 1 — — 10 Total $ 106 $ 21 $ — $ — $ — $ — $ 1 $ 229 $ 35 $ 49 $ 441 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 March 31, 2021 and December 31, 2020, Generation had a contract liability with ComEd for $24 million and $50 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. At March 31, 2021 and December 31, 2020, ComEd had a Current Payable to Generation of $26 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: March 31, 2021 December 31, 2020 ComEd $ 2,375 $ 2,541 PECO 490 475 Long-term debt to financing trusts The following table presents Long-term debt to financing trusts: March 31, 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	3 Months Ended
Planned Separation	Mar. 31, 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)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 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” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of March 31, 2021 and for the three months ended March 31, 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, except as otherwise disclosed. The
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.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
Regulatory Matters (Tables)	Mar. 31, 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 BGE - Maryland (b) May 15, 2020 (amended September 11, 2020) Electric 137 81 9.50 % December 16, 2020 January 1, 2021 Natural Gas 91 21 9.65 % __________ (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 in 2021, 2022, and 2023, respectively, and natural gas revenue requirement increases of $53 million, $11 million, and $10 million in 2021, 2022, and 2023, respectively. However, the MDPSC utilized certain tax benefits to fully offset the increases in 2021 so 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 revenue requirement increases in 2022 and 2023 and BGE cannot predict the outcome. 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 March 30, 2021 Electric 246 10.95 % Fourth quarter of 2021 PECO - Pennsylvania September 30, 2020 Natural Gas 69 10.95 % Second quarter of 2021 Pepco - District of Columbia (b) May 30, 2019 (amended June 1, 2020) Electric 136 9.7 % Second quarter of 2021 Pepco - Maryland (c) October 26, 2020 (amended March 31, 2021) Electric 104 10.2 % Second quarter of 2021 DPL - Delaware (d) March 6, 2020 (amended February 2, 2021) Electric 23 10.3 % Third quarter of 2021 ACE - New Jersey (e) December 9, 2020 (amended February 26, 2021) Electric 67 10.3 % Fourth quarter of 2021 __________ (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) Pepco filed the multi-year plan enhanced proposal as an alternative to address the impacts of COVID-19. Reflects a three-year cumulative multi-year plan for 2020 through 2022 and requested revenue requirement increases of $73 million in 2022 and $63 million in 2023, to recover capital investments made during 2018 through 2020 and planned capital investments through the end of 2022. (c) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024 and total requested revenue requirement increases of $52 million effective April 1, 2023 and $52 million effective April 1, 2024 to recover capital investments made in 2019 and 2020 and planned capital investments through March 31, 2024. (d) The rates went into effect on October 6, 2020, subject to refund. (e) Requested increases are before New Jersey sales and use tax. ACE intends to put rates into effect on September 8, 2021 subject to refund.
Public Utilities Transmission Rate Filings [Table Text Block]	For 2021, the following total increases were included in ComEd’s electric transmission formula rate update. PECO, BGE, Pepco, DPL, and ACE intend to file by the required deadline for the annual update. Registrant (a) Initial Revenue Requirement Increase Annual Reconciliation Increase Total Revenue Requirement Increase Allowed Return on Rate Base (b) Allowed ROE (c) ComEd $ 33 $ 12 $ 45 8.20 % 11.50 % (a) Rates are effective June 30, 2021 - May 31, 2022, subject to review by interested parties pursuant to review protocols of ComEd's tariff. (b) Represents the weighted average debt and equity return on transmission rate bases.
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 March 31, 2021 $ 49 $ — $ — $ 43 $ 6 $ 3 $ 3 $ — 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)	3 Months Ended
Revenue from Contracts with Customers (Tables)	Mar. 31, 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 March 31, 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 $ 233 $ 100 $ 56 $ 41 $ 330 $ 760 Generation 286 131 56 35 243 751 PHI 7 8 8 6 87 116 Pepco 5 6 6 5 70 92 DPL 1 1 1 — 9 12 ACE 1 1 1 1 8 12
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 months ended March 31, 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 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
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 months ended March 31, 2021 and 2020. As of March 31, 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 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 $ — $ — $ — $ — The following table reflects revenues recognized in the three months ended March 31, 2021 and 2020, which were included in contract liabilities at December 31, 2020 and 2019, respectively: Three Months Ended March 31, 2021 2020 Exelon $ 17 $ 9 Generation 39 19 PHI 2 — Pepco 2 —

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
Segment Information (Tables)	Mar. 31, 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 months ended March 31, 2021 and 2020 is as follows: Three Months Ended March 31, 2021 and 2020 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2021 Competitive businesses electric revenues $ 4,187 $ — $ — $ — $ — $ — $ (293) $ 3,894 Competitive businesses natural gas revenues 1,326 — — — — — 1,326 Competitive businesses other revenues 46 — — — — — (1) 45 Rate-regulated electric revenues — 1,535 661 632 1,170 — (10) 3,988 Rate-regulated natural gas revenues — — 228 342 71 — (4) 637 Shared service and other revenues — — — — 3 491 (494) — Total operating revenues $ 5,559 $ 1,535 $ 889 $ 974 $ 1,244 $ 491 $ (802) $ 9,890 2020 Competitive businesses electric revenues $ 3,752 $ — $ — $ — $ — $ — $ (326) $ 3,426 Competitive businesses natural gas revenues 672 — — — — — (3) 669 Competitive businesses other revenues 309 — — — — — (1) 308 Rate-regulated electric revenues — 1,439 604 613 1,104 — (12) 3,748 Rate-regulated natural gas revenues — — 209 324 64 — (2) 595 Shared service and other revenues — — — — 3 480 (482) 1 Total operating revenues $ 4,733 $ 1,439 $ 813 $ 937 $ 1,171 $ 480 $ (826) $ 8,747 Intersegment revenues (c) : 2021 $ 295 $ 6 $ 2 $ 6 $ 3 $ 487 $ (799) $ — 2020 330 5 2 6 3 479 (824) 1 Depreciation and amortization: Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon 2021 $ 940 $ 292 $ 86 $ 152 $ 210 $ 17 $ — $ 1,697 2020 304 273 86 143 194 21 — 1,021 Operating expenses: 2021 $ 6,672 $ 1,210 $ 679 $ 752 $ 1,058 $ 492 $ (781) $ 10,082 2020 4,400 1,151 625 688 1,000 481 (816) 7,529 Interest expense, net: 2021 $ 72 $ 96 $ 38 $ 34 $ 67 $ 79 $ — $ 386 2020 109 94 36 32 67 72 — 410 Income (loss) before income taxes: 2021 $ (947) $ 236 $ 177 $ 196 $ 136 $ (80) $ — $ (282) 2020 (547) 204 155 222 119 (69) 1 85 Income Taxes: 2021 $ (179) $ 39 $ 10 $ (13) $ 8 $ 116 $ — $ (19) 2020 (389) 36 15 41 11 (8) — (294) Net income (loss): 2021 $ (769) $ 197 $ 167 $ 209 $ 128 $ (196) $ — $ (264) 2020 (161) 168 140 181 108 (61) 1 376 Capital Expenditures: 2021 $ 382 $ 613 $ 295 $ 336 $ 456 $ 58 $ — $ 2,140 2020 558 506 259 283 376 34 — 2,016 Total assets: March 31, 2021 $ 47,326 $ 34,825 $ 12,937 $ 11,759 $ 24,387 $ 8,788 $ (10,022) $ 130,000 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 17 — 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 18 — 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 $ 553 $ 311 $ 310 $ — $ (4) $ 1,170 Rate-regulated natural gas revenues — 71 — — — 71 Shared service and other revenues — — — 95 (92) 3 Total operating revenues $ 553 $ 382 $ 310 $ 95 $ (96) $ 1,244 2020 Rate-regulated electric revenues $ 544 $ 286 $ 276 $ — $ (2) $ 1,104 Rate-regulated natural gas revenues — 64 — — — 64 Shared service and other revenues — — — 93 (90) 3 Total operating revenues $ 544 $ 350 $ 276 $ 93 $ (92) $ 1,171 Intersegment revenues (c) : 2021 $ 1 $ 2 $ 1 $ 95 $ (96) $ 3 2020 1 2 1 92 (93) 3 Depreciation and amortization: 2021 $ 102 $ 53 $ 47 $ 8 $ — $ 210 2020 95 48 43 9 (1) 194 Operating expenses: 2021 $ 466 $ 309 $ 282 $ 97 $ (96) $ 1,058 2020 462 284 251 93 (90) 1,000 Interest expense, net: 2021 $ 34 $ 15 $ 15 $ 3 $ — $ 67 2020 34 16 15 3 (1) 67 Income (loss) before income taxes: 2021 $ 65 $ 61 $ 14 $ (4) $ — $ 136 2020 (d) 57 52 14 (4) — 119 Income Taxes: 2021 $ 6 $ 5 $ — $ (3) $ — $ 8 2020 5 7 1 (2) — 11 Net income (loss): 2021 $ 59 $ 56 $ 14 $ (1) $ — $ 128 2020 52 45 13 (2) — 108 Capital Expenditures: 2021 $ 220 $ 112 $ 123 $ 1 $ — $ 456 2020 180 95 101 — — 376 Total assets: March 31, 2021 $ 9,493 $ 5,232 $ 4,679 $ 5,020 $ (37) $ 24,387 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 17 — Supplemental Financial Information for additional information on total utility taxes. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes in Other and Intersegment Eliminations have been adjusted by an offsetting $110 million in 2020.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended March 31, 2021 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 741 $ 433 $ 362 $ 605 $ 253 $ 190 $ 162 Small commercial & industrial 367 100 69 118 33 46 39 Large commercial & industrial 134 57 105 248 184 21 43 Public authorities & electric railroads 11 9 7 13 6 4 3 Other (a) 220 52 77 143 51 41 52 Total rate-regulated electric revenues (b) $ 1,473 $ 651 $ 620 $ 1,127 $ 527 $ 302 $ 299 Rate-regulated natural gas revenues Residential $ — $ 160 $ 216 $ 46 $ — $ 46 $ — Small commercial & industrial — 59 35 18 — 18 — Large commercial & industrial — — 54 2 — 2 — Transportation — 7 — 4 — 4 — Other (c) — 2 31 1 — 1 — Total rate-regulated natural gas revenues (d) $ — $ 228 $ 336 $ 71 $ — $ 71 $ — Total rate-regulated revenues from contracts with customers $ 1,473 $ 879 $ 956 $ 1,198 $ 527 $ 373 $ 299 Other revenues Revenues from alternative revenue programs $ 54 $ 10 $ 18 $ 46 $ 26 $ 9 $ 11 Other rate-regulated electric revenues (e) 8 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ 62 $ 10 $ 18 $ 46 $ 26 $ 9 $ 11 Total rate-regulated revenues for reportable segments $ 1,535 $ 889 $ 974 $ 1,244 $ 553 $ 382 $ 310 Three Months Ended March 31, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 701 $ 382 $ 339 $ 534 $ 236 $ 161 $ 137 Small commercial & industrial 362 99 67 115 35 43 37 Large commercial & industrial 134 53 103 253 188 23 42 Public authorities & electric railroads 13 7 7 15 9 3 3 Other (a) 211 58 79 169 60 54 55 Total rate-regulated electric revenues (b) $ 1,421 $ 599 $ 595 $ 1,086 $ 528 $ 284 $ 274 Rate-regulated natural gas revenues Residential $ — $ 150 $ 206 $ 40 $ — $ 40 $ — Small commercial & industrial — 51 34 17 — 17 — Large commercial & industrial — — 51 1 — 1 — Transportation — 6 — 4 — 4 — Other (c) — 1 9 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 208 $ 300 $ 64 $ — $ 64 $ — Total rate-regulated revenues from contracts with customers $ 1,421 $ 807 $ 895 $ 1,150 $ 528 $ 348 $ 274 Other revenues Revenues from alternative revenue programs $ 12 $ 2 $ 36 $ 18 $ 15 $ 1 $ 1 Other rate-regulated electric revenues (e) 6 3 3 3 1 1 1 Other rate-regulated natural gas revenues (e) — 1 3 — — — — Total other revenues $ 18 $ 6 $ 42 $ 21 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,439 $ 813 $ 937 $ 1,171 $ 544 $ 350 $ 276 __________ (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: • $6 million, $5 million at ComEd • $1 million, $2 million at PECO • $2 million, $6 million at BGE • $3 million, $3 million at PHI • $1 million, $1 million at Pepco • $2 million, $2 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 for both 2021 and 2020 • $4 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 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 March 31, 2021 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,174 $ (14) $ 1,160 $ 5 $ 1,165 Midwest 1,009 (11) 998 — 998 New York 382 (45) 337 — 337 ERCOT 353 (101) 252 5 257 Other Power Regions 1,172 268 1,440 (10) 1,430 Total Competitive Businesses Electric Revenues 4,090 97 4,187 — 4,187 Competitive Businesses Natural Gas Revenues 864 462 1,326 — 1,326 Competitive Businesses Other Revenues (c) 89 (43) 46 — 46 Total Generation Consolidated Operating Revenues $ 5,043 $ 516 $ 5,559 $ — $ 5,559 Three Months Ended March 31, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,264 $ (96) $ 1,168 $ 6 $ 1,174 Midwest 944 64 1,008 (6) 1,002 New York 335 (21) 314 — 314 ERCOT 155 28 183 7 190 Other Power Regions 1,007 72 1,079 (7) 1,072 Total Competitive Businesses Electric Revenues 3,705 47 3,752 — 3,752 Competitive Businesses Natural Gas Revenues 503 169 672 — 672 Competitive Businesses Other Revenues (c) 99 210 309 — 309 Total Generation Consolidated Operating Revenues $ 4,307 $ 426 $ 4,733 $ — $ 4,733 __________ (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 $84 million and gains of $179 million in 2021 and 2020, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 562 $ 5 $ 567 $ 559 $ 8 $ 567 Midwest 702 — 702 732 (5) 727 New York 240 2 242 189 4 193 ERCOT (1,036) (148) (1,184) 76 4 80 Other Power Regions 250 (33) 217 177 (19) 158 Total Revenues net of purchased power and fuel expense for Reportable Segments 718 (174) 544 1,733 (8) 1,725 Other (b) 231 174 405 296 8 304 Total Generation Revenues net of purchased power and fuel expense $ 949 $ — $ 949 $ 2,029 $ — $ 2,029 __________ (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 $175 million and gains of $132 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 $54 million in 2021; and • the elimination of intersegment RNF.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	3 Months Ended
Accounts Receivable (Tables)	Mar. 31, 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 March 31, 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 (a) 104 34 21 20 9 20 11 6 3 Less: Write-offs, net of recoveries (b) 28 1 15 6 1 5 2 3 — Balance as of March 31, 2021 $ 442 $ 65 $ 103 $ 130 $ 43 $ 101 $ 41 $ 25 $ 35 Three Months Ended March 31, 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 55 4 18 18 8 7 3 2 2 Less: Write-offs, net of recoveries (b) 20 3 6 7 2 2 1 — 1 Balance as of March 31, 2020 $ 278 $ 81 $ 71 $ 66 $ 18 $ 42 $ 15 $ 13 $ 14 _________ (a) For Generation, primarily relates to the impacts of the February 2021 extreme cold weather event. See Note 3 — Regulatory Matters for additional information. For the Utility Registrants, the increase is primarily as a result of increased receivable balances due to the colder weather and the increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnection of service to customers previously disconnected due to COVID-19. (b) Recoveries were not material to the Registrants. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended March 31, 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 10 — 1 4 1 4 2 1 1 Less: Write-offs, net of recoveries (a) 2 — — 1 1 — — — — Balance as of March 31, 2021 $ 79 $ — $ 22 $ 11 $ 9 $ 37 $ 15 $ 10 $ 12 Three Months Ended March 31, 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 8 — 3 1 2 2 1 — 1 Less: Write-offs, net of recoveries (a) 4 — 1 1 2 — — — — Balance as of March 31, 2020 $ 52 $ — $ 22 $ 7 $ 5 $ 18 $ 8 $ 4 $ 6 _________ (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 March 31, 2021 and December 31, 2020. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2021 $ 1,178 $ 671 $ 161 $ 102 $ 126 $ 118 $ 58 $ 38 $ 22 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: March 31, 2021 December 31, 2020 Derecognized receivables transferred at fair value $ 1,301 $ 1,139 Cash proceeds received 900 500 DPP 401 639 Three Months Ended March 31, 2021 Loss on sale of receivables (a) $ 17 _________ (a) Reflected in Operating and maintenance expense on Exelon's and Generation's Consolidated Statement of Operations and Comprehensive Income. Three Months Ended March 31, 2021 Proceeds from new transfers (a) $ 1,036 Cash collections received on DPP and reinvested in the Facility (b) 1,174 Cash collections reinvested in the Facility 2,210 _________ (a) Customer accounts receivable sold into the Facility were $2,375 million for the three months ended March 31, 2021. (b) Does not include the $400 million in cash proceeds received from the Purchasers in the first quarter of 2021. Three Months Ended March 31, 2021 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 1,011 $ — $ 266 $ 290 $ 199 $ 268 $ 166 $ 56 $ 46 Total receivables sold 69 81 — — — — — — — Related party transactions: Receivables purchased from Generation — — — — 12 — — — — Receivables sold to the Utility Registrants — 12 — — — — — — — Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total receivables purchased $ 781 $ — $ 280 $ 284 $ 195 $ 264 $ 165 $ 53 $ 46 Total receivables sold 507 749 — — — — — — — Related party transactions: Receivables purchased from Generation — — 34 67 69 72 51 13 8 Receivables sold to the Utility Registrants — 242 — — — — — — —

Early Plant Retirements (Tables

Early Plant Retirements (Tables)	3 Months Ended
Early Plant Retirements (Tables)	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Restructuring and Related Costs [Table Text Block]	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 further discussed below, and construction work-in-progress impairments, among other items. In addition, as a result of the decisions to early retire Byron and Dresden, there are 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. The total impact for the three months ended March 31, 2021 on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income is summarized in the table below. Income statement expense (pre-tax) Three Months Ended March 31, 2021 (a) Depreciation and amortization Accelerated depreciation (a) $ 620 Accelerated nuclear fuel amortization 54 Operating and maintenance Other charges 2 Contractual offset (b) (226) Total $ 450 _________ (a) Includes the accelerated depreciation of plant assets including any ARC. (b) Reflects contractual offset for ARO accretion and ARC depreciation. Based on the regulatory agreement with the ICC, decommissioning-related activities in the first quarter of 2021 have been offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset in 2021 resulted in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 10 - Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information.
Implications of Potential Early Plant Retirement on Balance Sheet [Table Text Block]	The following table provides the balance sheet amounts as of March 31, 2021 for Exelon's and Generation's significant assets and liabilities associated with the Braidwood and LaSalle nuclear plants. Current depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Braidwood LaSalle Total Asset Balances Materials and supplies inventory, net $ 83 $ 103 $ 186 Nuclear fuel inventory, net 165 264 429 Completed plant, net 1,379 1,566 2,945 Construction work in progress 33 70 103 Liability Balances Asset retirement obligation (577) (964) (1,541) NRC License First Renewal Term 2046 (Unit 1) 2042 (Unit 1) 2047 (Unit 2) 2043 (Unit 2)

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	3 Months Ended
Nuclear Decommissioning (Tables)	Mar. 31, 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 March 31, 2021: Nuclear decommissioning ARO at December 31, 2020 (a) $ 11,922 Accretion expense 124 Costs incurred related to decommissioning plants (20) Nuclear decommissioning ARO at March 31, 2021 (a) $ 12,026 _________ (a) Includes $80 million as the current portion of the ARO at March 31, 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)	3 Months Ended
Income Taxes (Tables)	Mar. 31, 2021
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
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 March 31, 2021 Exelon (a) Generation (a) ComEd (b) PECO (b) BGE (b),(c) PHI (b) Pepco (b) DPL (b) ACE (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 14.6 4.4 6.8 (1.6) (10.1) 6.1 5.5 6.4 6.9 Qualified NDT fund income (18.4) (5.5) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference 2.4 0.6 (0.1) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences 8.8 — (0.6) (10.5) (1.4) (1.5) (2.1) (0.7) (0.9) Production tax credits and other credits 6.7 1.8 (0.2) — (0.4) (0.2) (0.2) (0.1) (0.3) Noncontrolling interests 0.6 0.2 — — — — — — — Excess deferred tax amortization 27.9 — (6.9) (3.2) (15.5) (19.3) (15.1) (18.5) (28.7) Other (d) (56.9) (3.6) (3.5) (0.1) (0.1) (0.1) 0.1 0.3 2.2 Effective income tax rate 6.7% 18.9% 16.5% 5.6% (6.6)% 5.9% 9.2% 8.2% —% Three Months Ended March 31, 2020 Exelon (b) Generation (e) ComEd (b) PECO (b) BGE (b) PHI (b) Pepco (b) DPL (b) ACE (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 34.0 0.7 8.3 0.1 5.7 5.8 4.7 6.6 6.7 Qualified NDT fund income (235.8) 36.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.5) 0.5 (0.2) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (23.0) — (1.1) (8.4) (1.2) (1.4) (2.1) (0.7) (0.8) Production tax credits and other credits (9.9) 1.3 (0.2) — (0.2) — — — — Noncontrolling interests 10.6 (1.6) — — — — — — — Excess deferred tax amortization (71.7) — (10.5) (3.0) (7.3) (15.5) (14.2) (12.7) (18.8) Tax Settlements (79.1) 12.2 — — — — — — — Other 12.5 0.6 0.3 — 0.6 (0.6) (0.6) (0.5) (0.8) Effective income tax rate (345.9)% 71.1% 17.6% 9.7% 18.5% 9.2% 8.8% 13.5% 7.1% __________ (a) Exelon and Generation recognized a loss before income taxes for the quarter ended March 31, 2021. As a result, positive percentages represent an income tax benefit for the period presented. (b) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (c) 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. (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) Generation recognized a loss before income taxes for the quarter ended March 31, 2020. As a result, positive percentages represent an income tax benefit for the period presented.
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	PHI and ACE have the following unrecognized tax benefits as of March 31, 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 March 31, 2021 $ 52 $ 15 December 31, 2020 52 15

Retirement Benefits (Tables)

Retirement Benefits (Tables)	3 Months Ended
Retirement Benefits (Tables)	Mar. 31, 2021
Retirement Benefits [Abstract]
Calculation of Net Periodic Benefit Costs	A portion of the net periodic benefit cost for all plans is capitalized within the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three months ended March 31, 2021 and 2020. Pension Benefits OPEB Three Months Ended March 31, Three Months Ended March 31, 2021 2020 2021 2020 Components of net periodic benefit cost: Service cost $ 110 $ 97 $ 21 $ 23 Interest cost 161 189 28 38 Expected return on assets (336) (318) (40) (41) Amortization of: Prior service cost (credit) 1 1 (8) (31) Actuarial loss 150 128 9 12 Curtailment benefits — — (1) — Net periodic benefit cost $ 86 $ 97 $ 9 $ 1
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 March 31, Pension and OPEB Costs 2021 2020 Exelon $ 95 $ 98 Generation 26 27 ComEd 32 28 PECO 2 1 BGE 15 16 PHI 12 17 Pepco 2 3 DPL 1 1 ACE 3 3
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 months ended March 31, 2021 and 2020, respectively. Three Months Ended March 31, Savings Plans Matching Contributions 2021 2020 Exelon $ 33 $ 33 Generation 13 13 ComEd 8 7 PECO 3 3 BGE 2 2 PHI 3 3 Pepco 1 1 DPL 1 1

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
Derivative Financial Instruments (Tables)	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	The following table provides a summary of the derivative fair value balances recorded by Exelon, Generation, and ComEd as of March 31, 2021 and December 31, 2020: Exelon Generation ComEd March 31, 2021 Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 569 $ 2,566 $ 28 $ 24 $ (2,049) $ 569 $ — Mark-to-market derivative assets 488 1,400 5 45 (962) 488 — Total mark-to-market derivative assets 1,057 3,966 33 69 (3,011) 1,057 — Mark-to-market derivative liabilities (418) (2,472) (13) 49 2,049 (387) (31) Mark-to-market derivative liabilities (454) (1,179) (1) 28 962 (190) (264) Total mark-to-market derivative liabilities (872) (3,651) (14) 77 3,011 (577) (295) Total mark-to-market derivative net assets (liabilities) $ 185 $ 315 $ 19 $ 146 $ — $ 480 $ (295) 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. These amounts are not material and not reflected in the table above. (b) Of the collateral posted, $148 million and $209 million represents variation margin on the exchanges as of March 31, 2021 and December 31, 2020 respectively.
Economic Hedges (Commodity Price Risk)	For the three months ended March 31, 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 2021 2020 Income Statement Location Gain (Loss) Operating revenues $ (83) $ 175 Purchased power and fuel 265 (47) Total Exelon and Generation $ 182 $ 128
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 March 31, 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 March 31, 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 $ 431 $ 31 $ 400 — $ — Non-investment grade 43 4 39 No external ratings Internally rated — investment grade 146 1 145 Internally rated — non-investment grade 70 25 45 Total $ 690 $ 61 $ 629 — $ — Net Credit Exposure by Type of Counterparty As of March 31, 2021 Investor-owned utilities, marketers, power producers $ 451 Energy cooperatives and municipalities 123 Other 55 Total $ 629 _________ (a) As of March 31, 2021, credit collateral held from counterparties where Generation had credit exposure included $32 million of cash and $29 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 March 31, 2021 December 31, 2020 Gross fair value of derivative contracts containing this feature (a) $ (948) $ (834) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 518 537 Net fair value of derivative contracts containing this feature (c) $ (430) $ (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 March 31, 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. March 31, 2021 December 31, 2020 Cash collateral posted $ 232 $ 511 Letters of credit posted 242 226 Cash collateral held 101 110 Letters of credit held 41 40 Additional collateral required in the event of a credit downgrade below investment grade 1,379 1,432

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	3 Months Ended
Debt and Credit Agreements (Tables)	Mar. 31, 2021
Line of Credit Facility [Line Items]
Schedule of Long-term Debt Instruments [Table Text Block]	During the three months ended March 31, 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 Energy Efficiency Project Financing (a) 2.53 % May 31, 2021 1 Funding to install energy conservation measures for the Fort AP Hill 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. PECO First and Refunding Mortgage Bonds 3.05 % March 15, 2051 375 Funding for general corporate purposes. Pepco (b) First Mortgage Bonds 2.32 % March 30, 2031 150 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) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt. (b) On March 30, 2021, Pepco entered into a purchase agreement of First Mortgage Bonds of $125 million at 3.29% due on September 28, 2051. The closing date of the issuance is expected to occur in September 2021.
Commercial Paper [Member]
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 March 31, 2021 and December 31, 2020. PECO had no commercial paper borrowings as of both March 31, 2021 and December 31, 2020. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer March 31, 2021 December 31, 2020 March 31, 2021 December 31, 2020 Exelon (a)(b) $ 1,628 $ 1,031 0.52 % 0.25 % Generation (b) 1,337 340 0.60 % 0.27 % ComEd 135 323 0.16 % 0.23 % BGE 156 — 0.15 % — % PHI (c) — 368 — % 0.24 % Pepco — 35 — % 0.22 % DPL — 146 — % 0.24 % ACE — 187 — % 0.25 % __________ (a) Exelon Corporate had no outstanding commercial paper borrowings as of both March 31, 2021 and December 31, 2020. (b) Higher outstanding commercial paper primarily driven by increased liquidity needs from the February 2021 extreme cold weather event. See Note 3 – Regulatory Matters for additional information. (c) Represents the consolidated amounts of Pepco, DPL, and ACE.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
Fair Value of Financial Assets and Liabilities (Tables)	Mar. 31, 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 March 31, 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 on their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. March 31, 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 $ 38,529 $ 39,255 $ 3,115 $ 42,370 $ 36,912 $ 40,688 $ 3,064 $ 43,752 Generation 6,060 5,497 1,158 6,655 6,087 5,648 1,208 6,856 ComEd 9,674 10,853 — 10,853 8,983 11,117 — 11,117 PECO 4,125 4,491 50 4,541 3,753 4,553 50 4,603 BGE 3,665 3,991 — 3,991 3,664 4,366 — 4,366 PHI 7,577 6,050 1,907 7,957 7,006 6,099 1,806 7,905 Pepco 3,317 3,112 823 3,935 3,165 3,336 748 4,084 DPL 1,802 1,386 524 1,910 1,677 1,484 455 1,939 ACE 1,718 1,302 560 1,862 1,413 1,018 602 1,620 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 465 $ 465 $ 390 $ — $ 467 $ 467 ComEd 205 — 243 243 205 — 246 246 PECO 184 — 222 222 184 — 221 221 SNF Obligation Exelon $ 1,208 $ 979 $ — $ 979 $ 1,208 $ 909 $ — $ 909 Generation 1,208 979 — 979 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 March 31, 2021 and December 31, 2020: Exelon and Generation Exelon Generation As of March 31, 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) $ 968 $ — $ — $ — $ 968 $ 125 $ — $ — $ — $ 125 NDT fund investments Cash equivalents (b) 509 95 — — 604 509 95 — — 604 Equities 4,439 1,574 — 1,555 7,568 4,439 1,574 — 1,555 7,568 Fixed income Corporate debt (c) — 1,023 283 — 1,306 — 1,023 283 — 1,306 U.S. Treasury and agencies 2,030 41 — — 2,071 2,030 41 — — 2,071 Foreign governments — 51 — — 51 — 51 — — 51 State and municipal debt — 40 — — 40 — 40 — — 40 Other 40 35 — 1,285 1,360 40 35 — 1,285 1,360 Fixed income subtotal 2,070 1,190 283 1,285 4,828 2,070 1,190 283 1,285 4,828 Private credit — — 196 617 813 — — 196 617 813 Private equity — — — 532 532 — — — 532 532 Real estate — — — 686 686 — — — 686 686 NDT fund investments subtotal (d)(e) 7,018 2,859 479 4,675 15,031 7,018 2,859 479 4,675 15,031 Rabbi trust investments Cash equivalents 60 — — — 60 4 — — — 4 Mutual funds 95 — — — 95 31 — — — 31 Fixed income — 10 — — 10 — — — — — Life insurance contracts — 89 35 — 124 — 29 — — 29 Rabbi trust investments subtotal 155 99 35 — 289 35 29 — — 64 Investments in equities (f) 177 — — — 177 177 — — — 177 Commodity derivative assets Economic hedges 478 1,748 1,740 — 3,966 478 1,748 1,740 — 3,966 Proprietary trading — 16 17 — 33 — 16 17 — 33 Effect of netting and allocation of collateral (g)(h) (356) (1,387) (1,199) — (2,942) (356) (1,387) (1,199) — (2,942) Commodity derivative assets subtotal 122 377 558 — 1,057 122 377 558 — 1,057 DPP consideration — 401 — — 401 — 401 — — 401 Exelon Generation As of March 31, 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 8,440 3,736 1,072 4,675 17,923 7,477 3,666 1,037 4,675 16,855 Liabilities Commodity derivative liabilities Economic hedges (359) (1,642) (1,945) — (3,946) (359) (1,642) (1,650) — (3,651) Proprietary trading — (9) (5) — (14) — (9) (5) — (14) Effect of netting and allocation of collateral (g)(h) 252 1,532 1,304 — 3,088 252 1,532 1,304 — 3,088 Commodity derivative liabilities subtotal (107) (119) (646) — (872) (107) (119) (351) — (577) Deferred compensation obligation — (146) — — (146) — (43) — — (43) Total liabilities (107) (265) (646) — (1,018) (107) (162) (351) — (620) Total net assets $ 8,333 $ 3,471 $ 426 $ 4,675 $ 16,905 $ 7,370 $ 3,504 $ 686 $ 4,675 $ 16,235 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 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 $1,273 million and $409 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $93 million and $59 million at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $52 million and $53 million at March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $608 million and $171 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $29 million and $20 million at March 31, 2021 and December 31, 2020, respectively. (b) Includes $108 million and $116 million of cash received from outstanding repurchase agreements at March 31, 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 $(58) million and $(62) million as of March 31, 2021 and December 31, 2020, respectively, held in an investment vehicle primarily to hedge the equity option component of its convertible debt. (d) Includes derivative assets of less than $1 million and $2 million, which have total notional amounts of $2,049 million and $1,043 million at March 31, 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 $104 million and $181 million at March 31, 2021 and December 31, 2020, respectively, which include certain derivative assets that have notional amounts of $158 million and $104 million at March 31, 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. Generation recorded the fair value of these investments in Other current assets on Exelon's and Generation's Consolidated Balance Sheets based on the quoted market prices of the stocks at March 31, 2021 and December 31, 2020, which resulted in unrealized gains of $95 million and $186 million within Other, net in Exelon's and Generation's Consolidated Statement of Operations and Comprehensive Income for the three months ended March 31, 2021 and for the year ended December 31, 2020, respectively. (g) Collateral (received)/posted from counterparties, net of collateral paid to counterparties, totaled $(104) million, $145 million, and $105 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of March 31, 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) Of the collateral (received)/posted, $(148) million and $209 million represents variation margin on the exchanges as of March 31, 2021 and December 31, 2020, respectively. As of March 31, 2021, Exelon and Generation have outstanding commitments to invest in private credit, private equity, and real estate investments of approximately $298 million, $239 million, and $344 million, respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation hold investments without readily determinable fair values with carrying amounts of $61 million and $50 million as of March 31, 2021, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three months ended March 31, 2021. ComEd, PECO, and BGE ComEd PECO BGE As of March 31, 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) $ 300 $ — $ — $ 300 $ 7 $ — $ — $ 7 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 9 — — 9 11 — — 11 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 11 — — 11 Total assets 300 — — 300 16 13 — 29 11 — — 11 Liabilities Deferred compensation obligation — (8) — (8) — (9) — (9) — (6) — (6) Mark-to-market derivative liabilities (b) — — (295) (295) — — — — — — — — Total liabilities — (8) (295) (303) — (9) — (9) — (6) — (6) Total net assets (liabilities) $ 300 $ (8) $ (295) $ (3) $ 16 $ 4 $ — $ 20 $ 11 $ (6) $ — $ 5 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 $59 million and $83 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $40 million and $37 million at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $43 million at both March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $48 million and $18 million at March 31, 2021 and December 31, 2020, respectively. BGE excludes cash of $21 million and $24 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $1 million at both March 31, 2021 and December 31, 2020. (b) The Level 3 balance consists of the current and noncurrent liability of $31 million and $264 million, respectively, at March 31, 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 March 31, 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) $ 527 $ — $ — $ 527 $ 86 $ — $ — $ 86 Rabbi trust investments Cash equivalents 53 — — 53 55 — — 55 Mutual funds 15 — — 15 14 — — 14 Fixed income — 10 — 10 — 11 — 11 Life insurance contracts — 26 35 61 — 26 34 60 Rabbi trust investments subtotal 68 36 35 139 69 37 34 140 Total assets 595 36 35 666 155 37 34 226 Liabilities Deferred compensation obligation — (16) — (16) — (17) — (17) Total liabilities — (16) — (16) — (17) — (17) Total net assets $ 595 $ 20 $ 35 $ 650 $ 155 $ 20 $ 34 $ 209 Pepco DPL ACE As of March 31, 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) $ 128 $ — $ — $ 128 $ 50 $ — $ — $ 50 $ 349 $ — $ — $ 349 Rabbi trust investments Cash equivalents 53 — — 53 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 35 61 — — — — — — — — Rabbi trust investments subtotal 53 28 35 116 — — — — — — — — Total assets 181 28 35 244 50 — — 50 349 — — 349 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 181 $ 26 $ 35 $ 242 $ 50 $ — $ — $ 50 $ 349 $ — $ — $ 349 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 $72 million and $74 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at March 31, 2021 and December 31, 2020, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $34 million and $30 million at March 31, 2021 and December 31, 2020, respectively, and restricted cash of $5 million and none at March 31, 2021 and December 31, 2020, respectively. DPL excludes cash of $14 million and $15 million at March 31, 2021 and December 31, 2020, respectively. ACE excludes cash of $17 million at both March 31, 2021 and December 31, 2020, respectively, and includes long-term restricted cash of $9 million and $10 million at March 31, 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 months ended March 31, 2021 and 2020: Exelon Generation ComEd PHI and Pepco Three months ended March 31, 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 (276) 1 (278) (a) (277) — 1 — Included in noncurrent payables to affiliates — 1 — 1 — — (1) Included in regulatory assets 7 — — — 6 (b) — 1 Change in collateral (57) — (57) (57) — — — Purchases, sales, issuances and settlements Purchases 109 — 109 109 — — — Sales 1 — 1 1 — — — Settlements (20) (20) — (20) — — — Transfers out of Level 3 2 — 2 (c) 2 — — — Balance as of March 31, 2021 $ 426 $ 479 $ 207 $ 686 $ (295) $ 35 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2021 $ (147) $ 1 $ (149) $ (148) $ — $ 1 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 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 10 (1) 10 (a) 9 — 1 — Included in noncurrent payables to affiliates — (1) — (1) — — 1 Included in regulatory assets (14) — — — (13) (b) — (1) Change in collateral 1 — 1 1 — — — Purchases, sales, issuances and settlements Purchases 42 3 39 42 — — — Sales (22) — (22) (22) — — — Settlements (14) (14) — (14) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 15 — 15 (c) 15 — — — Balance as of March 31, 2020 $ 1,088 $ 498 $ 862 $ 1,360 $ (314) $ 42 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2020 $ 187 $ (1) $ 187 $ 186 $ — $ 1 $ — __________ (a) Includes a reduction for the reclassification of $129 million and $177 million of realized losses due to the settlement of derivative contracts for the three months ended March 31, 2021 and 2020 respectively. (b) Includes $2 million of decreases in fair value and an increase for realized losses due to settlements of $8 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2021. Includes $23 million of decrease in fair value and an increase for realized losses due to settlements of $10 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 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 months ended March 31, 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 for the three months ended March 31, 2021 $ (116) $ (162) $ 1 $ 1 $ (116) $ (162) $ 1 $ 1 Total unrealized (losses) gains for the three months ended March 31, 2021 (65) (84) 1 1 (65) (84) 1 1 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total gains (losses) for the three months ended March 31, 2020 $ 72 $ (62) $ 1 $ (1) $ 72 $ (62) $ (1) $ 1 Total unrealized gains (losses) gains for the three months ended March 31, 2020 205 (18) 1 (1) 205 (18) (1) 1
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 March 31, 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) $ 90 $ 245 Discounted Forward power $1.35 - $235 $32 $2.25 - $163 $30 Forward gas $1.42 - $8.18 $2.59 $1.57 - $7.88 $2.59 Option Volatility 11% - 116% 27% 11% - 237% 32% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 12 $ 23 Discounted Forward power $9 - $102 $30 $10 - $106 $27 Mark-to-market derivatives (Exelon and ComEd) $ (295) $ (301) Discounted Forward heat (c) 8x - 9x 8.85x 8x - 9x 8.85x Marketability 3% - 8% 4.93% 3% - 8% 4.93% Renewable 90% - 123% 99% 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 posted on level three positions of $105 million and $162 million as of March 31, 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)	3 Months Ended
Commitments and Contingencies (Tables)	Mar. 31, 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 March 31, 2021: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 79 64 53 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 March 31, 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 $ 1,639 $ 1,156 $ 483 $ — $ — $ — $ — Surety bonds (a) 1,077 919 158 — — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 29 — 3 4 6 5 11 Total commercial commitments $ 3,123 $ 2,075 $ 644 $ 4 $ 6 $ 5 $ 389 Generation Letters of credit $ 1,623 $ 1,141 $ 482 $ — $ — $ — $ — Surety bonds (a) 932 794 138 — — — — Total commercial commitments $ 2,555 $ 1,935 $ 620 $ — $ — $ — $ — ComEd Letters of credit $ 7 $ 7 $ — $ — $ — $ — $ — Surety bonds (a) 17 14 3 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 224 $ 21 $ 3 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 2 $ 2 $ — $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 180 $ 2 $ — $ — $ — $ — $ 178 BGE Letters of credit $ 3 $ 2 $ 1 $ — $ — $ — $ — Surety bonds (a) 3 3 — — — — — Total commercial commitments $ 6 $ 5 $ 1 $ — $ — $ — $ — PHI Surety bonds (a) $ 23 $ 20 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 29 — 3 4 6 5 11 Total commercial commitments $ 52 $ 20 $ 6 $ 4 $ 6 $ 5 $ 11 Pepco Surety bonds (a) $ 14 $ 14 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 10 — 1 1 2 2 4 Total commercial commitments $ 24 $ 14 $ 1 $ 1 $ 2 $ 2 $ 4 DPL Surety bonds (a) $ 5 $ 2 $ 3 $ — $ — $ — $ — Guaranteed lease residual values (b) 12 — 1 2 3 2 4 Total commercial commitments $ 17 $ 2 $ 4 $ 2 $ 3 $ 2 $ 4 ACE Surety bonds (a) $ 4 $ 4 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 11 $ 4 $ 1 $ 1 $ 1 $ 1 $ 3 __________ (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 $73 million guaranteed by Exelon and PHI, of which $25 million, $30 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 March 31, 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 within their respective Consolidated Balance Sheets: March 31, 2021 December 31, 2020 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 473 $ 306 $ 483 $ 314 Generation 119 — 121 — ComEd 281 280 293 293 PECO 23 21 23 21 BGE 6 5 2 — PHI 44 — 44 — Pepco 42 — 42 — DPL 1 — 1 — ACE 1 — 1 —

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Tables)	3 Months Ended
Changes in Accumulated Other Comprehensive Income (Tables)	Mar. 31, 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 March 31, 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 — (2) 1 (1) Amounts reclassified from AOCI — 55 — 55 Net current-period OCI — 53 1 54 Ending balance $ (5) $ (3,319) $ (22) $ (3,346) Three Months Ended March 31, 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 (1) (7) (8) (16) Amounts reclassified from AOCI — 37 — 37 Net current-period OCI (1) 30 (8) 21 Ending balance $ (3) $ (3,135) $ (35) $ (3,173) _________
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 March 31, 2021 2020 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 1 $ 4 Actuarial loss reclassified to periodic benefit cost (19) (17) Pension and non-pension postretirement benefit plans valuation adjustment — 3

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
Variable Interest Entities (Tables)	Mar. 31, 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 March 31, 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. March 31, 2021 December 31, 2020 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 175 $ 175 $ — $ — $ 98 $ 98 $ — $ — Restricted cash and cash equivalents 37 33 4 4 47 44 3 3 Accounts receivable Customer 145 145 — — 148 148 — — Other 35 35 — — 36 36 — — Unamortized energy contract assets 22 22 — — 22 22 — — Inventories, net Materials and supplies 242 242 — — 244 244 — — Assets held for sale (b) — — — — 101 101 — — Other current assets 448 443 5 — 674 669 5 — Total current assets 1,104 1,095 9 4 1,370 1,362 8 3 Property, plant, and equipment, net 5,747 5,747 — — 5,803 5,803 — — Nuclear decommissioning trust funds 3,089 3,089 — — 3,007 3,007 — — Unamortized energy contract assets 243 243 — — 249 249 — — Other noncurrent assets 47 38 9 9 52 42 10 10 Total noncurrent assets 9,126 9,117 9 9 9,111 9,101 10 10 Total assets (c) $ 10,230 $ 10,212 $ 18 $ 13 $ 10,481 $ 10,463 $ 18 $ 13 Long-term debt due within one year $ 90 $ 69 $ 21 $ 16 $ 94 $ 68 $ 26 $ 21 Accounts payable 95 95 — — 81 81 — — Accrued expenses 67 67 — — 70 70 — — Unamortized energy contract liabilities 3 3 — — 4 4 — — Liabilities held for sale (b) — — — — 16 16 — — Other current liabilities 1 1 — — 5 5 — — Total current liabilities 256 235 21 16 270 244 26 21 Long-term debt 861 861 — — 889 889 — — Asset retirement obligations 2,347 2,347 — — 2,318 2,318 — — Other noncurrent liabilities 116 116 — — 129 129 — — Total noncurrent liabilities 3,324 3,324 — — 3,336 3,336 — — Total liabilities (d) $ 3,580 $ 3,559 $ 21 $ 16 $ 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) Ex elon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $22 million and $22 million, non-current unamortized energy contract assets of $222 million and $249 million, Assets held for sale of $0 million and $9 million, and other unrestricted assets of $1 million and $1 million as of March 31, 2021 and December 31, 2020, respectively (d) Exelon’s and Generation’s balances include liabilities with recourse of $2 million a nd $8 million as of March 31, 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: March 31, 2021 December 31, 2020 Commercial Equity Total Commercial Equity Total Total assets (a) $ 789 $ 386 $ 1,175 $ 777 $ 401 $ 1,178 Total liabilities (a) 95 218 313 61 223 284 Exelon's ownership interest in VIE (a) — 150 150 — 157 157 Other ownership interests in VIE (a) 694 18 712 716 21 737 _________ (a) These items represent amounts on 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 March 31, 2021 and December 31, 2020.

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	3 Months Ended
Supplemental Financial Information (Tables)	Mar. 31, 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 March 31, 2021 Operating lease income $ 4 $ 3 $ 1 $ 1 Variable lease income 64 64 — — Three Months Ended March 31, 2020 Operating lease income $ 5 $ 3 $ 1 $ 1 Variable lease income 69 69 — —
Taxes Other Than Income Taxes	Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2021 Utility taxes (a) $ 217 $ 24 $ 59 $ 35 $ 25 $ 74 $ 67 $ 6 $ 1 Property 154 68 8 4 42 32 21 10 1 Payroll 61 28 7 4 5 7 2 1 — Three Months Ended March 31, 2020 Utility taxes (a) $ 218 $ 26 $ 60 $ 31 $ 26 $ 75 $ 69 $ 6 $ — Property 150 69 7 4 39 31 21 9 1 Payroll 63 31 7 4 4 8 2 1 1 __________ (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 March 31, 2021 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 291 $ 291 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 203 203 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units (82) (82) — — — — — — — Non-Regulatory Agreement Units (66) (66) — — — — — — — Regulatory offset to NDT fund-related activities (b) (167) (167) — — — — — — — Decommissioning-related activities 179 179 — — — — — — — AFUDC — Equity 28 — 4 6 7 11 9 1 1 Non-service net periodic benefit cost 20 — — — — — — — — Three Months Ended March 31, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory Agreement Units $ 47 $ 47 $ — $ — $ — $ — $ — $ — $ — Non-Regulatory Agreement Units 82 82 — — — — — — — Net unrealized gains on NDT funds Regulatory Agreement Units (932) (932) — — — — — — — Non-Regulatory Agreement Units (706) (706) — — — — — — — Regulatory offset to NDT fund-related activities (b) 709 709 — — — — — — — Decommissioning-related activities (800) (800) — — — — — — — AFUDC — Equity 23 — 6 3 5 9 6 1 2 Non-service net periodic benefit cost 10 — — — — — — — — __________ (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, including the elimination of income taxes related to all NDT fund activity for those units. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
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 Three Months Ended March 31, 2021 Property, plant, and equipment (a) $ 1,522 $ 928 $ 239 $ 82 $ 106 $ 154 $ 67 $ 42 $ 37 Amortization of regulatory assets (a) 160 — 53 4 46 56 35 11 10 Amortization of intangible assets, net (a) 15 12 — — — — — — — Amortization of energy contract assets and liabilities (b) 4 3 — — — — — — — Nuclear fuel (c) 276 276 — — — — — — — ARO accretion (d) 127 127 — — — — — — — Total depreciation, amortization and accretion $ 2,104 $ 1,346 $ 292 $ 86 $ 152 $ 210 $ 102 $ 53 $ 47 Three Months Ended March 31, 2020 Property, plant, and equipment (a) $ 856 $ 290 $ 228 $ 79 $ 97 $ 144 $ 64 $ 38 $ 34 Amortization of regulatory assets (a) 149 — 45 7 46 50 31 10 9 Amortization of intangible assets, net (a) 16 14 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 231 231 — — — — — — — ARO accretion (d) 124 124 — — — — — — — Total depreciation, amortization and accretion $ 1,378 $ 661 $ 273 $ 86 $ 143 $ 194 $ 95 $ 48 $ 43 __________ (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 Three Months Ended March 31, 2021 Pension and non-pension postretirement benefit costs $ 95 $ 26 $ 32 $ 2 $ 14 $ 12 $ 2 $ 1 $ 3 Allowance for credit losses 85 34 13 24 4 10 5 4 1 Other decommissioning-related activity (a) (322) (332) — — — — — — — Energy-related options (b) 17 17 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) (129) — (54) (10) (18) (46) (26) (9) (11) Long-term incentive plan 32 — — — — — — — — Amortization of operating ROU asset 37 21 — — 7 7 1 3 1 AFUDC - Equity (28) — (4) (6) (7) (11) (9) (1) (1) Three Months Ended March 31, 2020 Pension and non-pension postretirement benefit costs $ 98 $ 27 $ 28 $ 1 $ 15 $ 17 $ 3 $ 1 $ 3 Allowance for credit losses 45 4 7 17 7 10 4 3 3 Other decommissioning-related activity (a) 128 128 — — — — — — — Energy-related options (b) 6 6 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (d) (71) — (17) — (35) (19) (15) (4) — Long-term incentive plan (7) — — — — — — — — Amortization of operating ROU asset 51 35 — — 8 5 2 2 1 AFUDC - Equity (23) — (6) (3) (5) (9) (6) (1) (2) __________ (a) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income, and income taxes related to all NDT fund activity for these units. See Note 10 — Asset Retirement Obligations of the Exelon 2020 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (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, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO and ACE, reflects the change in regulatory assets and liabilities associated with their transmission formula rates. See Note 3 — Regulatory Matters for additional information. (d) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution and energy efficiency formula rates. For BGE, Pepco, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms. See Note 3 — Regulatory Matters for additional information. 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 March 31, 2021 Cash and cash equivalents $ 1,908 $ 721 $ 86 $ 48 $ 21 $ 558 $ 134 $ 64 $ 353 Restricted cash and cash equivalents 374 41 270 7 1 37 33 — 4 Restricted cash included in other long-term assets 52 — 43 — — 9 — — 9 Total cash, restricted cash, and cash equivalents $ 2,334 $ 762 $ 399 $ 55 $ 22 $ 604 $ 167 $ 64 $ 366 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 March 31, 2020 Cash and cash equivalents $ 1,457 $ 821 $ 514 $ 31 $ 11 $ 49 $ 18 $ 7 $ 8 Restricted cash and cash equivalents 414 150 211 7 1 37 33 — 3 Restricted cash included in other long-term assets 121 — 108 — — 12 — — 12 Total cash, restricted cash, and cash equivalents $ 1,992 $ 971 $ 833 $ 38 $ 12 $ 98 $ 51 $ 7 $ 23 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 March 31, 2021 Compensation-related accruals (a) $ 581 $ 210 $ 91 $ 42 $ 49 $ 73 $ 26 $ 15 $ 12 Taxes accrued 540 279 70 18 50 108 92 10 12 Interest accrued 424 76 65 36 41 79 37 20 20 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)	3 Months Ended
Related Party Transactions (Tables)	Mar. 31, 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 March 31, 2021 2020 Operating revenues from affiliates: ComEd (a)(b) $ 78 $ 90 PECO (c) 42 37 BGE (d) 72 99 PHI 100 103 Pepco (e) 75 79 DPL (f) 21 22 ACE (g) 4 2 Other 3 1 Total operating revenues from affiliates (Generation) $ 295 $ 330 __________ (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 months ended March 31, 2021, ComEd’s Purchased power from Generation of $84 million is recorded as Operating revenues from ComEd of $78 million and as Purchased power and fuel from ComEd of $6 million at Generation. For the three months ended March 31, 2020 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $90 million and as Purchased power and fuel from ComEd of $7 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 March 31, Three Months Ended March 31, 2021 2020 2021 2020 Exelon BSC $ 124 $ 113 PHISCO 17 14 Generation BSC $ 144 $ 140 10 11 ComEd BSC 71 72 45 42 PECO BSC 39 37 17 16 BGE BSC 43 41 20 28 PHI BSC 39 37 32 16 PHISCO — — 17 14 Pepco BSC 22 21 13 6 PHISCO 30 30 7 6 DPL BSC 14 13 10 5 PHISCO 25 24 5 4 ACE BSC 12 11 8 4 PHISCO 22 22 5 4
Current Receivables From/Payables To Affiliates	The following tables present current receivables from affiliates and current payables to affiliates: March 31, 2021 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE Pepco DPL ACE BSC PHISCO Other Total Generation $ 17 $ — $ — $ — $ — $ — $ 84 $ — $ 24 $ 125 ComEd $ 50 (a) — — — — — 49 — 5 104 PECO 15 — — — — — 24 — 7 46 BGE 11 1 — — — — 30 — 1 43 PHI — 1 — — — — — 7 — 10 18 Pepco 12 1 — — — — 16 14 1 44 DPL 2 — — — — — 11 11 — 24 ACE 8 — — — — — 8 10 1 27 Other 8 1 — — — — 1 — — 10 Total $ 106 $ 21 $ — $ — $ — $ — $ 1 $ 229 $ 35 $ 49 $ 441 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 March 31, 2021 and December 31, 2020, Generation had a contract liability with ComEd for $24 million and $50 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. At March 31, 2021 and December 31, 2020, ComEd had a Current Payable to Generation of $26 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: March 31, 2021 December 31, 2020 ComEd $ 2,375 $ 2,541 PECO 490 475
Long Term Debt to Financing Trusts	The following table presents Long-term debt to financing trusts: March 31, 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_2

Mergers, Acquisitions, and Dispositions - Narrative (Details) $ in Millions	Apr. 01, 2014USD ($)	Mar. 31, 2021USD ($)MW	Dec. 31, 2020
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
Deconsolidation, Gain (Loss), Amount		68
Albany Green Energy biomass facility \| Minimum [Member]
Business Dispositions
Impairment of Long-Lived Assets to be Disposed of		135
Albany Green Energy biomass facility \| Maximum [Member]
Business Dispositions
Impairment of Long-Lived Assets to be Disposed of		$ 150
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
Deconsolidation, Gain (Loss), Amount		68
Exelon Generation Co L L C [Member] \| Albany Green Energy biomass facility \| Minimum [Member]
Business Dispositions
Impairment of Long-Lived Assets to be Disposed of		135
Exelon Generation Co L L C [Member] \| Albany Green Energy biomass facility \| Maximum [Member]
Business Dispositions
Impairment of Long-Lived Assets to be Disposed of		$ 150
CENG [Member]
Business Acquisitions
Equity Method Investment, Ownership Percentage		50.01%	50.01%
Payments of Capital Distribution	$ 400
Due from Affiliates	400	$ 632
CENG Preferred Distribution Return		8.50%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.99%
CENG [Member] \| Nine Mile Point
Business Acquisitions
Equity Method Investment, Ownership Percentage		82.00%
CENG [Member] \| Exelon Generation Co L L C [Member]
Business Acquisitions
Equity Method Investment, Ownership Percentage		50.01%	50.01%
Payments of Capital Distribution	400
Due from Affiliates	$ 400	$ 632
CENG Preferred Distribution Return		8.50%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.99%
CENG [Member] \| Exelon Generation Co L L C [Member] \| Nine Mile Point
Business Acquisitions
Equity Method Investment, Ownership Percentage		82.00%

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) - USD ($)	Feb. 15, 2021	Mar. 31, 2021
Texas-based generating assets
Regulatory Matters Additional Narrative Information [Line Items]
Operating and maintenance		$ 880,000,000
Market Payment Shortfall in Collections		28,000,000
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		2,900,000,000
Market-wide Limit Recovery of Default		2,500,000
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		28,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		106,000,000
Commonwealth Edison Co [Member] \| Electric Distribution Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		55,000,000
Commonwealth Edison Co [Member] \| Energy Efficiency Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		38,000,000
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		56,000,000
PECO Energy Co [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		48,000,000
PECO Energy Co [Member] \| Vacation Accrual
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets		9,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets
Increase (Decrease) in Regulatory Liabilities		(82,000,000)
Baltimore Gas and Electric Company [Member] \| Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities		(93,000,000)
Baltimore Gas and Electric Company [Member] \| electric energy and natural gas cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities		$ 9,000,000

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Completed Rate Cases (Details) - USD ($) $ in Millions	Dec. 16, 2020	Dec. 09, 2020	Sep. 11, 2020	Apr. 16, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
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, Interim Rate Increase (Decrease), Amount		$ 50
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
Baltimore Gas and Electric Company [Member] \| Maryland 2020 Electric Distribution Base Rate Case [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)			$ 137
Approved Revenue Requirement Increase (Decrease)	$ 81
Approved Return on Equity, Percentage	9.50%
Public Utilities, Interim Rate Increase (Decrease), Amount					$ 42	$ 39	$ 59
Baltimore Gas and Electric Company [Member] \| Maryland 2020 Gas Distribution Base Rate Case [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)			$ 91
Approved Revenue Requirement Increase (Decrease)	$ 21
Approved Return on Equity, Percentage	9.65%
Public Utilities, Interim Rate Increase (Decrease), Amount					$ 10	$ 11	$ 53

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Pending Rate Cases (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 30, 2021	Feb. 26, 2021	Feb. 02, 2021	Sep. 30, 2020	Jun. 01, 2020	Apr. 16, 2020	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
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%
PECO Energy Co [Member] \| Pennsylvania 2020 Natural Gas Distribution Base Rate Case
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)					$ 69
Requested Return on Equity, Percentage					10.95%
Potomac Electric Power Company [Member] \| District of Columbia 2019 Electric Distribution Base Rate Case [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended						$ 136			$ 63	$ 73
Requested Return on Equity, Percentage						9.70%
Potomac Electric Power Company [Member] \| Maryland 2020 Electric Distribution Base Rate Case [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended	$ 104							$ 52	$ 52
Requested Return on Equity, Percentage	10.20%
Delmarva Power and Light Company [Member] \| Delaware 2020 Electric Distribution Base Rate Case [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended				$ 23
Requested Return on Equity, Percentage				10.30%
Atlantic City Electric Company [Member] \| New Jersey 2020 Electric Distribution Base Rate Case
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended			$ 67
Requested Return on Equity, Percentage			10.30%

Regulatory Matters - Annual Ele

Regulatory Matters - Annual Electric Transmission Fillings (Details) - Commonwealth Edison Co [Member] - 2021 Transmission Formula Rate Annual Update [Domain] $ in Millions	Apr. 16, 2021USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 33
Annual Reconciliation Decrease	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%

Regulatory Matters - Capitalize

Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Mar. 31, 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	$ 49	$ 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	43	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	6	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	3	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
	Mar. 31, 2021	Mar. 31, 2020
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	$ 144	$ 174
Consideration (received) due, contract assets	(16)	(19)
Revenues recognized, contract assets	13	17
Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination	12
Ending Balance - Contract Assets	153	172
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	151	33
Consideration received (due), contract liabilities	20	20
Revenues recognized, contract liabilities	(27)	(24)
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	3
Ending Balance - Contract Liabilities	147	29
Contract with Customer, Performance Obligation Satisfied in Previous Period	17	9
Exelon Generation Co L L C [Member]
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	144	174
Consideration (received) due, contract assets	(16)	(19)
Revenues recognized, contract assets	13	17
Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination	12
Ending Balance - Contract Assets	153	172
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	84	71
Consideration received (due), contract liabilities	31	55
Revenues recognized, contract liabilities	(64)	(70)
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	3
Ending Balance - Contract Liabilities	54	56
Contract with Customer, Performance Obligation Satisfied in Previous Period	39	19
Pepco Holdings LLC [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	118	0
Consideration received (due), contract liabilities	0	0
Revenues recognized, contract liabilities	(2)	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0
Ending Balance - Contract Liabilities	116	0
Contract with Customer, Performance Obligation Satisfied in Previous Period	2	0
Potomac Electric Power Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	94	0
Consideration received (due), contract liabilities	0	0
Revenues recognized, contract liabilities	(2)	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0
Ending Balance - Contract Liabilities	92	0
Contract with Customer, Performance Obligation Satisfied in Previous Period	2	0
Delmarva Power and Light Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	12	0
Consideration received (due), contract liabilities	0	0
Revenues recognized, contract liabilities	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0
Ending Balance - Contract Liabilities	12	0
Atlantic City Electric Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	12	0
Consideration received (due), contract liabilities	0	0
Revenues recognized, contract liabilities	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0
Ending Balance - Contract Liabilities	$ 12	$ 0

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Mar. 31, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 760
Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	751
Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	116
Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	92
Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	12
Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	12
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	233
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 \| Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	286
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 \| Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 \| 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, Start Date [Axis]: 2021-01-01 \| 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, Start Date [Axis]: 2021-01-01 \| 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, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	100
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	131
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, 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, 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, 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, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	56
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	56
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, 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, 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, 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, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	41
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	35
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, 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, 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, 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, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	330
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	243
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, 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, 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, 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

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
Segment Information - Narrative (Details)	Mar. 31, 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
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues		$ 9,890	$ 8,747
Revenue from Related Parties		0	1
Depreciation and Amortization		1,697	1,021
Operating Expenses		10,082	7,529
Interest expense, net		386	410
Income (Loss) before income taxes		(282)	85
Income taxes		(19)	(294)
Net income (loss)		(264)	376
Capital expenditures		2,140	2,016
Assets	[1]	130,000		$ 129,317
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		5,559	4,733
Revenue from Related Parties		295	330
Income (Loss) before income taxes		(947)	(547)
Income taxes		(179)	(389)
Net income (loss)		(769)	(161)
Capital expenditures		382	558
Assets	[2]	47,326		48,094
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		1,244	1,171
Revenue from Related Parties		3	3
Income (Loss) before income taxes		136	119
Income taxes		8	11
Net income (loss)		128	108
Capital expenditures		456	376
Assets	[3]	24,387		23,736
Commonwealth Edison Co Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		78	90
PECO Energy Co Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		42	37
Baltimore Gas And Electric Company Affiliate [Member] \| Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		72	99
Operating Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		46	18
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(802)	(826)
Revenue from Related Parties		(799)	(824)
Depreciation and Amortization		0	0
Operating Expenses		(781)	(816)
Interest expense, net		0	0
Income (Loss) before income taxes		0	1
Income taxes		0	0
Net income (loss)		0	1
Capital expenditures		0	0
Assets		(10,022)		(10,165)
Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		(96)	(92)
Revenue from Related Parties		(96)	(93)
Depreciation and Amortization		0	(1)
Operating Expenses		(96)	(90)
Interest expense, net		0	(1)
Income (Loss) before income taxes		0	0
Income taxes		0	0
Net income (loss)		0	0
Capital expenditures		0	0
Assets		(37)		(33)
Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		5,559	4,733
Depreciation and Amortization		940	304
Operating Expenses		6,672	4,400
Interest expense, net		72	109
Income (Loss) before income taxes		(947)	(547)
Income taxes		(179)	(389)
Net income (loss)		(769)	(161)
Capital expenditures		382	558
Assets		47,326		48,094
Exelon Generation Co L L C [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		295	330
Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		1,535	1,439
Depreciation and Amortization		292	273
Operating Expenses		1,210	1,151
Interest expense, net		96	94
Income (Loss) before income taxes		236	204
Income taxes		39	36
Net income (loss)		197	168
Capital expenditures		613	506
Assets		34,825		34,466
Commonwealth Edison Co [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6	5
PECO Energy Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		889	813
Depreciation and Amortization		86	86
Operating Expenses		679	625
Interest expense, net		38	36
Income (Loss) before income taxes		177	155
Income taxes		10	15
Net income (loss)		167	140
Capital expenditures		295	259
Assets		12,937		12,531
PECO Energy Co [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2	2
Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		974	937
Depreciation and Amortization		152	143
Operating Expenses		752	688
Interest expense, net		34	32
Income (Loss) before income taxes		196	222
Income taxes		(13)	41
Net income (loss)		209	181
Capital expenditures		336	283
Assets		11,759		11,650
Baltimore Gas and Electric Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6	6
Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		1,244	1,171
Depreciation and Amortization		210	194
Operating Expenses		1,058	1,000
Interest expense, net		67	67
Income (Loss) before income taxes		136	119
Income taxes		8	11
Net income (loss)		128	108
Capital expenditures		456	376
Assets		24,387		23,736
Pepco Holdings LLC [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3	3
Potomac Electric Power Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		553	544
Depreciation and Amortization		102	95
Operating Expenses		466	462
Interest expense, net		34	34
Income (Loss) before income taxes		65	57
Income taxes		6	5
Net income (loss)		59	52
Capital expenditures		220	180
Assets		9,493		9,264
Potomac Electric Power Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1	1
Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		382	350
Depreciation and Amortization		53	48
Operating Expenses		309	284
Interest expense, net		15	16
Income (Loss) before income taxes		61	52
Income taxes		5	7
Net income (loss)		56	45
Capital expenditures		112	95
Assets		5,232		5,140
Delmarva Power and Light Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2	2
Atlantic City Electric Company [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		310	276
Depreciation and Amortization		47	43
Operating Expenses		282	251
Interest expense, net		15	15
Income (Loss) before income taxes		14	14
Income taxes		0	1
Net income (loss)		14	13
Capital expenditures		123	101
Assets		4,679		4,286
Atlantic City Electric Company [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1	1
Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues		491	480
Depreciation and Amortization		17	21
Operating Expenses		492	481
Interest expense, net		79	72
Income (Loss) before income taxes		(80)	(69)
Income taxes		116	(8)
Net income (loss)		(196)	(61)
Capital expenditures		58	34
Assets		8,788		9,005
Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		95	93
Depreciation and Amortization		8	9
Operating Expenses		97	93
Interest expense, net		3	3
Income (Loss) before income taxes		(4)	(4)
Income taxes		(3)	(2)
Net income (loss)		(1)	(2)
Capital expenditures		1	0
Assets		5,020		$ 5,079
Corporate and Other [Member] \| Corporate, Non-Segment [Member] \| Pepco Holdings LLC [Member] \| Revision of Prior Period, Adjustment [Member]
Segment Reporting Information [Line Items]
Income (Loss) before income taxes			110
Corporate and Other [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		487	479
Corporate and Other [Member] \| Intersegment Eliminations [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		95	92
Competitive businesses electric revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3,894	3,426
Competitive businesses electric revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(293)	(326)
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		4,187	3,752
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
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
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
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
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
Competitive businesses natural gas revenues Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,326	669
Competitive businesses natural gas revenues Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax			(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		1,326	672
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
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
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
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
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
Competitive businesses other revenues [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		45	308
Competitive businesses other revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(1)	(1)
Competitive businesses other revenues [Member] \| Exelon Generation Co L L C [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		46	309
Competitive businesses other revenues [Member] \| Commonwealth Edison Co [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		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
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
Competitive businesses other revenues [Member] \| Pepco Holdings LLC [Member] \| Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		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
Rate-regulated electric revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3,988	3,748
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,124	1,086
Rate-regulated electric revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(10)	(12)
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)	(2)
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
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		1,535	1,439
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		661	604
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		632	613
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		1,170	1,104
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		553	544
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		311	286
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		310	276
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
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
Rate-regulated natural gas revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		637	595
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		71	64
Rate-regulated natural gas revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(4)	(2)
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
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
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
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		228	209
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		342	324
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		71	64
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
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		71	64
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
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
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
Shared service and other revenues [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0	1
Shared service and other revenues [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(494)	(482)
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		(92)	(90)
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
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
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
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
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	3
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
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
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
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		491	480
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		$ 95	$ 93

[1]	Exelon’s consolidated assets include $9,985 million and $10,200 million at March 31, 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 $3,578 million and $3,598 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,967 million and $10,182 million at March 31, 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 $3,557 million and $3,572 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both March 31, 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 $21 million and $26 million at March 31, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 9,890	$ 8,747
Revenue from Related Parties	0	1
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,165	1,174
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	998	1,002
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	337	314
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	257	190
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,430	1,072
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,187	3,752
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	1,326	672
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	46	309
Unrealized Gain (Loss) on Securities	(84)	179
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	5,559	4,733
Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,160	1,168
Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	998	1,008
Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	337	314
Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	252	183
Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,440	1,079
Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,187	3,752
Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	1,326	672
Operating Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	175	132
Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	5,559	4,733
Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	46	309
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(802)	(826)
Revenue from Related Parties	(799)	(824)
Intersegment Eliminations [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	5	6
Intersegment Eliminations [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	(6)
Intersegment Eliminations [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	5	7
Intersegment Eliminations [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(10)	(7)
Intersegment Eliminations [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,174	1,264
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,009	944
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	382	335
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	353	155
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,172	1,007
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,090	3,705
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	864	503
Revenue from Contract with Customer [Member] \| Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	5,043	4,307
Revenue from Contract with Customer [Member] \| Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	89	99
Other [Member] \| Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(14)	(96)
Other [Member] \| Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(11)	64
Other [Member] \| Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(45)	(21)
Other [Member] \| Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(101)	28
Other [Member] \| Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	268	72
Other [Member] \| Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	97	47
Other [Member] \| Operating Segment [Member] \| Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	462	169
Other [Member] \| Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	516	426
Other [Member] \| Corporate, Non-Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ (43)	$ 210

Segment Information - Generat_2

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 567	$ 567
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	702	727
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	242	193
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	(1,184)	80
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	217	158
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	544	1,725
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	405	304
Unrealized Gain (Loss) on Securities	(84)	179
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	949	2,029
Operating Segment [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
RNF from external customers	562	559
Operating Segment [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
RNF from external customers	702	732
Operating Segment [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
RNF from external customers	240	189
Operating Segment [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
RNF from external customers	(1,036)	76
Operating Segment [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
RNF from external customers	250	177
Operating Segment [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
RNF from external customers	718	1,733
Operating Segment [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	231	296
Unrealized Gain (Loss) on Securities	175	132
Accelerated nuclear fuel amortization	54
Operating Segment [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
RNF from external customers	949	2,029
Intersegment Eliminations [Member] \| Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	5	8
Intersegment Eliminations [Member] \| Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0	(5)
Intersegment Eliminations [Member] \| Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	2	4
Intersegment Eliminations [Member] \| Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(148)	4
Intersegment Eliminations [Member] \| Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(33)	(19)
Intersegment Eliminations [Member] \| Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(174)	(8)
Intersegment Eliminations [Member] \| Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	174	8
Intersegment Eliminations [Member] \| Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0	$ 0

Segment Information - Electric

Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue, Major Customer [Line Items]
Revenues	$ 9,890,000,000	$ 8,747,000,000
Revenue from Related Parties	0	1,000,000
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,535,000,000	1,439,000,000
Revenue from Related Parties	6,000,000	5,000,000
Commonwealth Edison Co [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	54,000,000	12,000,000
Commonwealth Edison Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,473,000,000	1,421,000,000
Commonwealth Edison Co [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	62,000,000	18,000,000
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	889,000,000	813,000,000
Revenue from Related Parties	2,000,000	2,000,000
PECO Energy Co [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10,000,000	2,000,000
PECO Energy Co [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	879,000,000	807,000,000
PECO Energy Co [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	10,000,000	6,000,000
PECO Energy Co [Member] \| Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1,000,000	2,000,000
PECO Energy Co [Member] \| Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	974,000,000	937,000,000
Revenue from Related Parties	6,000,000	6,000,000
Baltimore Gas and Electric Company [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	18,000,000	36,000,000
Baltimore Gas and Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	956,000,000	895,000,000
Baltimore Gas and Electric Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	18,000,000	42,000,000
Baltimore Gas and Electric Company [Member] \| Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2,000,000	6,000,000
Baltimore Gas and Electric Company [Member] \| Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4,000,000	3,000,000
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,244,000,000	1,171,000,000
Revenue from Related Parties	3,000,000	3,000,000
Pepco Holdings LLC [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	46,000,000	18,000,000
Pepco Holdings LLC [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,198,000,000	1,150,000,000
Pepco Holdings LLC [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	46,000,000	21,000,000
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	553,000,000	544,000,000
Revenue from Related Parties	1,000,000	1,000,000
Potomac Electric Power Company [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,000,000	15,000,000
Potomac Electric Power Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	527,000,000	528,000,000
Potomac Electric Power Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	26,000,000	16,000,000
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	382,000,000	350,000,000
Revenue from Related Parties	2,000,000	2,000,000
Delmarva Power and Light Company [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9,000,000	1,000,000
Delmarva Power and Light Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	373,000,000	348,000,000
Delmarva Power and Light Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	9,000,000	2,000,000
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	310,000,000	276,000,000
Revenue from Related Parties	1,000,000	1,000,000
Atlantic City Electric Company [Member] \| Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11,000,000	1,000,000
Atlantic City Electric Company [Member] \| Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	299,000,000	274,000,000
Atlantic City Electric Company [Member] \| Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	11,000,000	2,000,000
Rate-regulated electric revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,988,000,000	3,748,000,000
Rate-regulated electric revenues [Member] \| Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,475,000,000	1,422,000,000
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	1,473,000,000	1,421,000,000
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	8,000,000	6,000,000
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	741,000,000	701,000,000
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	367,000,000	362,000,000
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	134,000,000	134,000,000
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	11,000,000	13,000,000
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	220,000,000	211,000,000
Rate-regulated electric revenues [Member] \| PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	649,000,000	600,000,000
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	651,000,000	599,000,000
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	0	3,000,000
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	433,000,000	382,000,000
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	100,000,000	99,000,000
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	57,000,000	53,000,000
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	9,000,000	7,000,000
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	52,000,000	58,000,000
Rate-regulated electric revenues [Member] \| Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	620,000,000	595,000,000
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	620,000,000	595,000,000
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	0	3,000,000
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	362,000,000	339,000,000
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	69,000,000	67,000,000
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	105,000,000	103,000,000
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	7,000,000	7,000,000
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	77,000,000	79,000,000
Rate-regulated electric revenues [Member] \| Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,124,000,000	1,086,000,000
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	1,127,000,000	1,086,000,000
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	0	3,000,000
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	605,000,000	534,000,000
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	118,000,000	115,000,000
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	248,000,000	253,000,000
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	13,000,000	15,000,000
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	143,000,000	169,000,000
Rate-regulated electric revenues [Member] \| Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	526,000,000	528,000,000
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	527,000,000	528,000,000
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	0	1,000,000
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	253,000,000	236,000,000
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	33,000,000	35,000,000
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	184,000,000	188,000,000
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	6,000,000	9,000,000
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	51,000,000	60,000,000
Rate-regulated electric revenues [Member] \| Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	300,000,000	283,000,000
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	302,000,000	284,000,000
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	0	1,000,000
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	190,000,000	161,000,000
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	46,000,000	43,000,000
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	21,000,000	23,000,000
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	4,000,000	3,000,000
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	41,000,000	54,000,000
Rate-regulated electric revenues [Member] \| Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	298,000,000	274,000,000
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	299,000,000	274,000,000
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	1,000,000
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	162,000,000	137,000,000
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	39,000,000	37,000,000
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	43,000,000	42,000,000
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	3,000,000	3,000,000
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	52,000,000	55,000,000
Rate-regulated natural gas revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	637,000,000	595,000,000
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
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
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
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
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
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
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
Rate-regulated natural gas revenues [Member] \| PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	228,000,000	209,000,000
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	228,000,000	208,000,000
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	1,000,000
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	160,000,000	150,000,000
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	59,000,000	51,000,000
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
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	7,000,000	6,000,000
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	2,000,000	1,000,000
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	330,000,000	300,000,000
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	336,000,000	300,000,000
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	0	3,000,000
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	216,000,000	206,000,000
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	35,000,000	34,000,000
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	54,000,000	51,000,000
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
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	31,000,000	9,000,000
Rate-regulated natural gas revenues [Member] \| Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	71,000,000	64,000,000
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	71,000,000	64,000,000
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
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	46,000,000	40,000,000
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	18,000,000	17,000,000
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	2,000,000	1,000,000
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	4,000,000	4,000,000
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	1,000,000	2,000,000
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
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
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
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
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
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
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
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	71,000,000	64,000,000
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	71,000,000	64,000,000
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
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	46,000,000	40,000,000
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	18,000,000	17,000,000
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	2,000,000	1,000,000
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	4,000,000	4,000,000
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	1,000,000	2,000,000
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
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
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
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
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
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
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

Accounts Receivable - Narrative

Accounts Receivable - Narrative (Details) - Sale of accounts receivable [Member] - USD ($) $ in Millions	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	$ 1,301		$ 1,139	$ 1,200
Cash proceeds received	900	$ 250	500	500
DPP consideration	401		639	650
March 29, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum borrowing capacity	900
Cash proceeds received	150
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]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	1,301		1,139	1,200
Cash proceeds received	900	$ 250	500	500
DPP consideration	401		$ 639	$ 650
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
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

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	$ (85)	$ (45)
Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(34)	(4)
Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(13)	(7)
PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(24)	(17)
Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(4)	(7)
Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(10)	(10)
Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(5)	(4)
Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(4)	(3)
Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current period provision for expected credit losses	(1)	(3)
Customer accounts receivable
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	366	243
Current period provision for expected credit losses	104	55
Writeoffs, net of recoveries	28	20
Ending balance	442	278
Customer accounts receivable \| Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	32	80
Current period provision for expected credit losses	34	4
Writeoffs, net of recoveries	1	3
Ending balance	65	81
Customer accounts receivable \| Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	97	59
Current period provision for expected credit losses	21	18
Writeoffs, net of recoveries	15	6
Ending balance	103	71
Customer accounts receivable \| PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	116	55
Current period provision for expected credit losses	20	18
Writeoffs, net of recoveries	6	7
Ending balance	130	66
Customer accounts receivable \| Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	35	12
Current period provision for expected credit losses	9	8
Writeoffs, net of recoveries	1	2
Ending balance	43	18
Customer accounts receivable \| Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	86	37
Current period provision for expected credit losses	20	7
Writeoffs, net of recoveries	5	2
Ending balance	101	42
Customer accounts receivable \| Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	32	13
Current period provision for expected credit losses	11	3
Writeoffs, net of recoveries	2	1
Ending balance	41	15
Customer accounts receivable \| Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	22	11
Current period provision for expected credit losses	6	2
Writeoffs, net of recoveries	3	0
Ending balance	25	13
Customer accounts receivable \| Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	32	13
Current period provision for expected credit losses	3	2
Writeoffs, net of recoveries	0	1
Ending balance	35	14
Other receivables
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	71	48
Current period provision for expected credit losses	10	8
Writeoffs, net of recoveries	2	4
Ending balance	79	52
Other receivables \| Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	0	0
Current period provision for expected credit losses	0	0
Writeoffs, net of recoveries	0	0
Ending balance	0	0
Other receivables \| Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	21	20
Current period provision for expected credit losses	1	3
Writeoffs, net of recoveries	0	1
Ending balance	22	22
Other receivables \| PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	8	7
Current period provision for expected credit losses	4	1
Writeoffs, net of recoveries	1	1
Ending balance	11	7
Other receivables \| Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	9	5
Current period provision for expected credit losses	1	2
Writeoffs, net of recoveries	1	2
Ending balance	9	5
Other receivables \| Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	33	16
Current period provision for expected credit losses	4	2
Writeoffs, net of recoveries	0	0
Ending balance	37	18
Other receivables \| Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	13	7
Current period provision for expected credit losses	2	1
Writeoffs, net of recoveries	0	0
Ending balance	15	8
Other receivables \| Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	9	4
Current period provision for expected credit losses	1	0
Writeoffs, net of recoveries	0	0
Ending balance	10	4
Other receivables \| Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	11	5
Current period provision for expected credit losses	1	1
Writeoffs, net of recoveries	0	0
Ending balance	$ 12	$ 6

Accounts Receivable - Unbilled

Accounts Receivable - Unbilled Customer Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 1,178	$ 998
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	671	258
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	161	218
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	102	147
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	126	197
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	118	178
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	58	87
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	38	62
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 22	$ 29

Accounts Receivable - Purchases

Accounts Receivable - Purchases and Sales of Accounts Receivable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Feb. 17, 2021	Dec. 31, 2020	Apr. 08, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loss on sale receivables	$ 17
Proceeds from new transfers	1,036
Cash collections received on deferred purchase price and reinvested in the Facility	1,174
Cash collections reinvested in the Facility	2,210
Accounts Receivable, Purchase	1,011	$ 781
Accounts Receivable, Sale	69	507
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loss on sale receivables	17
Proceeds from new transfers	1,036
Cash collections received on deferred purchase price and reinvested in the Facility	1,174
Cash collections reinvested in the Facility	2,210
Accounts Receivable, Purchase	0	0
Accounts Receivable, Sale	81	749
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	266	280
Accounts Receivable, Sale	0	0
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	290	284
Accounts Receivable, Sale	0	0
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	199	195
Accounts Receivable, Sale	0	0
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	268	264
Accounts Receivable, Sale	0	0
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	166	165
Accounts Receivable, Sale	0	0
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	56	53
Accounts Receivable, Sale	0	0
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Purchase	46	46
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	12	69
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	12	$ 242
Sale of accounts receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derecognized receivables transferred at fair value	1,301			$ 1,139	$ 1,200
Cash proceeds received	900		$ 250	500	500
DPP consideration	401			639	650
Transfer of Financial Assets Accounted for as Sales, Additional Transfers	2,375
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	1,301			1,139	1,200
Cash proceeds received	900		$ 250	500	500
DPP consideration	401			$ 639	$ 650
Transfer of Financial Assets Accounted for as Sales, Additional Transfers	2,375
Sale of Accounts Receivable_Three Months Ended Q1 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cash proceeds received	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

Early Plant Retirements - Narra

Early Plant Retirements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 1,697	$ 1,021
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 940	$ 304
Salem [Member] \| Nuclear Plant [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Ownership interest	42.59%
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 20
Generation New England [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	20
Facility Closing [Member] \| Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Severance Liability	81
Severance Costs			$ 81
Facility Closing [Member] \| Midwest Asset Group [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Severance Liability	$ 81
Severance Costs			$ 81

Early Plant Retirements - Preta

Early Plant Retirements - Pretax Expense (Details) - Facility Closing [Member] - Byron Dresden $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Accelerated depreciation	$ 620
Accelerated nuclear fuel amortization	54
Operating and maintenance	2
Asset Retirement Obligation Contractual Offset	(226)
Restructuring and Related Cost, Incurred Cost	450
Exelon Generation Co L L C [Member]
Accelerated depreciation	620
Accelerated nuclear fuel amortization	54
Operating and maintenance	2
Asset Retirement Obligation Contractual Offset	(226)
Restructuring and Related Cost, Incurred Cost	$ 450

Early Plant Retirements - Impli

Early Plant Retirements - Implications of Potential Early Plant Retirement on Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	$ 1,427	$ 1,425
Property, plant and equipment, net	82,588	82,584
Braidwood [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	83
Nuclear fuel inventory, net	165
Property, plant and equipment, net	1,379
Construction work in progress	33
Asset retirement obligation	(577)
LaSalle [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Inventory, Raw Materials, Net of Reserves	103
Nuclear fuel inventory, net	264
Property, plant and equipment, net	1,566
Construction work in progress	70
Asset retirement obligation	(964)
Braidwood LaSalle [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	186
Nuclear fuel inventory, net	429
Property, plant and equipment, net	2,945
Construction work in progress	103
Asset retirement obligation	(1,541)
Exelon Generation Co L L C [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	973	978
Property, plant and equipment, net	21,311	$ 22,214
Exelon Generation Co L L C [Member] \| Braidwood [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	83
Nuclear fuel inventory, net	165
Property, plant and equipment, net	1,379
Construction work in progress	33
Asset retirement obligation	(577)
Exelon Generation Co L L C [Member] \| LaSalle [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Inventory, Raw Materials, Net of Reserves	103
Nuclear fuel inventory, net	264
Property, plant and equipment, net	1,566
Construction work in progress	70
Asset retirement obligation	(964)
Exelon Generation Co L L C [Member] \| Braidwood LaSalle [Member] \| Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	186
Nuclear fuel inventory, net	429
Property, plant and equipment, net	2,945
Construction work in progress	103
Asset retirement obligation	$ (1,541)

Nuclear Decommissioning - Narra

Nuclear Decommissioning - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 14,688	$ 14,464
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	14,688	14,464
Assets, Total [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	14,927	14,599
Assets, Total [Member] \| Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	14,927	14,599
Other Current Assets [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	239	134
Other Current Assets [Member] \| Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 239	$ 134

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	$ 127	$ 124
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	127	$ 124
Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	11,922
Accretion expense	124
Costs incurred related to decommissioning plants	(20)
ARO ending balance	12,026
Current portion of ARO	80		$ 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	124
Costs incurred related to decommissioning plants	(20)
ARO ending balance	12,026
Current portion of ARO	$ 80		$ 80

Asset Impairments - Narrative (

Asset Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 1	$ 8
Net income (loss) attributable to noncontrolling interests	25	(206)
Deferred income taxes and amortization of investment tax credits	(142)	(245)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	1	8
Net income (loss) attributable to noncontrolling interests	24	(206)
Deferred income taxes and amortization of investment tax credits	(123)	$ (329)
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	0
Antelope Valley [Member] \| Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	0
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

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) $ in Millions	Mar. 31, 2021USD ($)
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

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	14.60%	34.00%
Qualified nuclear decommissioning trust fund income	(18.40%)	(235.80%)
Amortization of investment tax credit, including deferred taxes on basis difference	2.40%	(4.50%)
Plant basis differences	8.80%	(23.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	6.70%	(9.90%)
Noncontrolling interests	0.60%	10.60%
Excess deferred tax amortization	27.90%	(71.70%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		(79.10%)
Other	(56.90%)	12.50%
Effective income tax rate	6.70%	(345.90%)
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	4.40%	0.70%
Qualified nuclear decommissioning trust fund income	(5.50%)	36.40%
Amortization of investment tax credit, including deferred taxes on basis difference	0.60%	0.50%
Plant basis differences	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	1.80%	1.30%
Noncontrolling interests	0.20%	(1.60%)
Excess deferred tax amortization	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		12.20%
Other	(3.60%)	0.60%
Effective income tax rate	18.90%	71.10%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.80%	8.30%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.20%)
Plant basis differences	(0.60%)	(1.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.20%)	(0.20%)
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(6.90%)	(10.50%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	(3.50%)	0.30%
Effective income tax rate	16.50%	17.60%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(1.60%)	0.10%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%
Plant basis differences	(10.50%)	(8.40%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(3.20%)	(3.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	(0.10%)	0.00%
Effective income tax rate	5.60%	9.70%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(10.10%)	5.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Plant basis differences	(1.40%)	(1.20%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	(0.20%)
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(15.50%)	(7.30%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	(0.10%)	0.60%
Effective income tax rate	(6.60%)	18.50%
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.10%	5.80%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Plant basis differences	(1.50%)	(1.40%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.20%)	0.00%
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(19.30%)	(15.50%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	(0.10%)	(0.60%)
Effective income tax rate	5.90%	9.20%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.50%	4.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%
Plant basis differences	(2.10%)	(2.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.20%)	0.00%
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(15.10%)	(14.20%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	0.10%	(0.60%)
Effective income tax rate	9.20%	8.80%
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.40%	6.60%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Plant basis differences	(0.70%)	(0.70%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.10%)	0.00%
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(18.50%)	(12.70%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	0.30%	(0.50%)
Effective income tax rate	8.20%	13.50%
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.90%	6.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Plant basis differences	(0.90%)	(0.80%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.30%)	0.00%
Noncontrolling interests	0.00%	0.00%
Excess deferred tax amortization	(28.70%)	(18.80%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Other	2.20%	(0.80%)
Effective income tax rate	0.00%	7.10%

Income Taxes - Unrecognized Tax

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

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended
Retirement Benefits - Narrative (Details) $ in Millions	Mar. 31, 2021USD ($)
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
	Mar. 31, 2021	Mar. 31, 2020
Amortization of:
Net periodic benefit cost	$ (20)	$ (10)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	110	97
Interest cost	161	189
Expected return on assets	(336)	(318)
Amortization of:
Prior service cost (credit)	1	1
Actuarial loss	150	128
Curtailment benefits	0	0
Net periodic benefit cost	86	97
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	23
Interest cost	28	38
Expected return on assets	(40)	(41)
Amortization of:
Prior service cost (credit)	(8)	(31)
Actuarial loss	9	12
Curtailment benefits	(1)	0
Net periodic benefit cost	$ 9	$ 1

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	$ 95	$ 98
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	95	98
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	26	27
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	26	27
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	32	28
Commonwealth Edison Co [Member] \| Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	32	28
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	2	1
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
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	14	15
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	15	16
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	12	17
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
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	2	3
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	3
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	1	1
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	1
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Costs	3	3
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

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 33	$ 33
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	13	13
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	8	7
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	3	3
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	2	2
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	3	3
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	1	1
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 1	$ 1

Derivative Financial Instrume_3

Derivative Financial Instruments - Narrative (Details) MWh in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Jun. 30, 2012MWh	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Derivative [Line Items]
Derivative, Notional Amount		$ 158	$ 104
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,379	1,432
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		158	104
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,379	1,432
Commonwealth Edison Co [Member]
Derivative [Line Items]
Long-term Purchase Commitment, Minimum Energy Volume Required \| MWh	1.3
PECO Energy Co [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		32
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		48
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 12
Minimum [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		94.00%
Maximum [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		97.00%
Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 563	665
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 563	$ 665

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Mark-to-market derivative assets, current	$ 568	$ 644
Derivative Asset, Noncurrent	491	555
Mark-to-market derivative liabilities, current	(422)	(295)
Mark-to-market derivative liabilities, noncurrent	(453)	(473)
Margin Deposit Assets	148	209
Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	569	639
Derivative Asset, Noncurrent	488	554
Total mark-to-market derivative assets	1,057	1,193
Mark-to-market derivative liabilities, current	(418)	(293)
Mark-to-market derivative liabilities, noncurrent	(454)	(472)
Total mark-to-market derivative liabilities	(872)	(765)
Total mark-to-market derivative net assets (liabilities)	185	428
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	569	644
Derivative Asset, Noncurrent	491	555
Mark-to-market derivative liabilities, current	(392)	(262)
Mark-to-market derivative liabilities, noncurrent	(190)	(205)
Margin Deposit Assets	148	209
Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	569	639
Derivative Asset, Noncurrent	488	554
Total mark-to-market derivative assets	1,057	1,193
Mark-to-market derivative liabilities, current	(387)	(260)
Mark-to-market derivative liabilities, noncurrent	(190)	(204)
Total mark-to-market derivative liabilities	(577)	(464)
Total mark-to-market derivative net assets (liabilities)	480	729
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities, current	(31)	(33)
Mark-to-market derivative liabilities, noncurrent	(264)	(268)
Collateral [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	24	103
Derivative Asset, Noncurrent	45	64
Total mark-to-market derivative assets	69	167
Mark-to-market derivative liabilities, current	49	131
Mark-to-market derivative liabilities, noncurrent	28	118
Total mark-to-market derivative liabilities	77	249
Total mark-to-market derivative net assets (liabilities)	146	416
Netting [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	(2,049)	(2,261)
Derivative Asset, Noncurrent	(962)	(1,015)
Total mark-to-market derivative assets	(3,011)	(3,276)
Mark-to-market derivative liabilities, current	2,049	2,261
Mark-to-market derivative liabilities, noncurrent	962	1,015
Total mark-to-market derivative liabilities	3,011	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	2,566	2,757
Derivative Asset, Noncurrent	1,400	1,501
Total mark-to-market derivative assets	3,966	4,258
Mark-to-market derivative liabilities, current	(2,472)	(2,629)
Mark-to-market derivative liabilities, noncurrent	(1,179)	(1,335)
Total mark-to-market derivative liabilities	(3,651)	(3,964)
Total mark-to-market derivative net assets (liabilities)	315	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	(31)	(33)
Mark-to-market derivative liabilities, noncurrent	(264)	(268)
Total mark-to-market derivative liabilities	(295)	(301)
Total mark-to-market derivative net assets (liabilities)	(295)	(301)
Not Designated as Hedging Instrument [Member] \| Exelon Generation Co L L C [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	28	40
Derivative Asset, Noncurrent	5	4
Total mark-to-market derivative assets	33	44
Mark-to-market derivative liabilities, current	(13)	(23)
Mark-to-market derivative liabilities, noncurrent	(1)	(2)
Total mark-to-market derivative liabilities	(14)	(25)
Total mark-to-market derivative net assets (liabilities)	$ 19	$ 19

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 178	$ 132
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	178	127
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	182	128
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	182	128
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(83)	175
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Operating Revenue [Member] \| Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(83)	175
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Purchased Power And Fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	265	(47)
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	$ 265	$ (47)

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	Mar. 31, 2021USD ($)
Derivative [Line Items]
Cash Collateral Held	$ 32
Letters Of Credit Held	29
Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	431
Non-investment grade	43
Internally rated - investment grade	146
Internally rated - non-investment grade	70
Total	690
Credit Collateral [Member]
Derivative [Line Items]
Investment grade	31
Non-investment grade	4
Internally rated - investment grade	1
Internally rated - non-investment grade	25
Total	61
Net Exposure [Member]
Derivative [Line Items]
Investment grade	400
Non-investment grade	39
Internally rated - investment grade	145
Internally rated - non-investment grade	45
Total	629
Investor-owned utilities, marketers and power producers	451
Energy Cooperatives And Municipalities	123
Other	55
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Total	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Total	$ 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	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	$ (948)	$ (834)
Offsetting Fair Value of In-the-Money Contracts Under Master Netting Agreements	518	537
Derivative liabilities, fair value	$ (430)	$ (297)

Derivative Financial Instrume_8

Derivative Financial Instruments Derivative Financial Instruments - Summary of Cash Collateral and Letters of Credit (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 232	$ 511
Derivative, Collateral, Right to Reclaim Securities	242	226
Derivative, Collateral, Obligation to Return Cash	101	110
Derivative, Collateral, Obligation to Return Securities	41	40
Incremental Collateral For Loss Of Investment Grade Credit Rating	1,379	1,432
Exelon Generation Co L L C [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	232	511
Derivative, Collateral, Right to Reclaim Securities	242	226
Derivative, Collateral, Obligation to Return Cash	101	110
Derivative, Collateral, Obligation to Return Securities	41	40
Incremental Collateral For Loss Of Investment Grade Credit Rating	$ 1,379	$ 1,432

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Short-term Debt \| 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
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
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
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
ShortTermDebt03232017 \| Corporate [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
London Interbank Offered Rate (LIBOR) [Member] \| Short-term Debt \| 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] \| 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] \| 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] \| ShortTermDebt03232017 \| Corporate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65%

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Commercial Paper	$ 1,628	$ 1,031
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.52%	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	$ 1,337	$ 340
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.60%	0.27%
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 135	$ 323
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.16%	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	$ 156	$ 0
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.15%	0.00%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 368
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.24%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 35
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.22%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 146
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.24%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 187
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.25%

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	Mar. 31, 2021USD ($)
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] \| EEPF253April2021 \| Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
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
PECO Energy Co [Member] \| FMB305Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.05%
Debt Instrument, Face Amount	$ 375
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) $ in Millions	Mar. 31, 2021USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 61
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	50
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	298
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	298
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	239
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	239
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	344
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	$ 344

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	Mar. 31, 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	1,208	1,208
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	38,529	36,912
Long-term debt to financing trust	390	390
Spent Nuclear Fuel Obligation, Noncurrent	1,208	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)	42,370	43,752
Long-term debt to financing trust	465	467
Spent Nuclear Fuel Obligation, Noncurrent	979	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)	39,255	40,688
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	979	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)	3,115	3,064
Long-term debt to financing trust	465	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	1,208	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)	6,060	6,087
Spent Nuclear Fuel Obligation, Noncurrent	1,208	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)	6,655	6,856
Spent Nuclear Fuel Obligation, Noncurrent	979	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)	5,497	5,648
Spent Nuclear Fuel Obligation, Noncurrent	979	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)	1,158	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)	9,674	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)	10,853	11,117
Long-term debt to financing trust	243	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)	10,853	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	243	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)	4,125	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)	4,541	4,603
Long-term debt to financing trust	222	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)	4,491	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	222	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)	3,665	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)	3,991	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)	3,991	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)	7,577	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)	7,957	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)	6,050	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)	1,907	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)	3,317	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)	3,935	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)	3,112	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)	823	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)	1,802	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)	1,910	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)	1,386	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)	524	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)	1,718	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)	1,862	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)	1,302	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)	$ 560	$ 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	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	$ 422	$ 295
Derivative Liability, Noncurrent	453	473
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	1	2
Derivative Asset, Notional Amount	2,049	1,043
Margin Deposit Assets	(148)	(209)
Derivative, Notional Amount	158	104
Unrealized Gain (Loss) on Investments	95	186
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,273	409
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	93	59
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	52	53
Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	104	181
Financial Instruments Sold, Not yet Purchased, Corporate Debt	(58)	(62)
Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	968	686
DPP consideration	401	639
Assets, Fair Value Disclosure	17,923	17,776
Deferred Compensation Liability, Current and Noncurrent	(146)	(145)
Total Liabilities	(1,018)	(910)
Fair Value, Net Asset (Liability)	16,905	16,866
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	(872)	(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	(3,946)	(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	(14)	(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	3,088	3,525
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	15,031	14,780
Fair Value, Recurring [Member] \| Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	604	305
Fair Value, Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	177	195
Fair Value, Recurring [Member] \| Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,828	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	1,306	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	2,071	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	51	56
Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	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	1,360	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	813	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	532	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	686	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	289	283
Fair Value, Recurring [Member] \| Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	60	60
Fair Value, Recurring [Member] \| Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	95	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	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	124	121
Fair Value, Recurring [Member] \| Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,057	1,193
Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	3,966	4,258
Fair Value, Recurring [Member] \| Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	33	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	(2,942)	(3,109)
Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,568	7,525
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	(104)	(67)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	968	686
DPP consideration	0	0
Assets, Fair Value Disclosure	8,440	7,137
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(107)	(142)
Fair Value, Net Asset (Liability)	8,333	6,995
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	(107)	(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	(359)	(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
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	252	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	7,018	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	509	210
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	177	195
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	2,070	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
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	2,030	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
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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	40	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
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
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
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	155	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	60	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	95	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
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
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	122	138
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	478	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
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	(356)	(607)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,439	3,886
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	145	321
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
DPP consideration	401	639
Assets, Fair Value Disclosure	3,736	5,052
Deferred Compensation Liability, Current and Noncurrent	(146)	(145)
Total Liabilities	(265)	(176)
Fair Value, Net Asset (Liability)	3,471	4,876
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	(119)	(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	(1,642)	(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	(9)	(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	1,532	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	2,859	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	95	95
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
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	1,190	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	1,023	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	41	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	51	56
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	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	35	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
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
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
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	99	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
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
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	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	89	87
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	377	334
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,748	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	16	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	(1,387)	(1,597)
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,574	2,077
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	105	162
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
DPP consideration	0	0
Assets, Fair Value Disclosure	1,072	1,252
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(646)	(592)
Fair Value, Net Asset (Liability)	426	660
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	(646)	(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	(1,945)	(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	(5)	(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	1,304	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	479	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
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
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	283	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	283	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
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
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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
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	196	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
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
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	35	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
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
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
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	35	34
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	558	721
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,740	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	17	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	(1,199)	(905)
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
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
DPP consideration	0	0
Assets, Fair Value Disclosure	4,675	4,335
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	4,675	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
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
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
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
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	4,675	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
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
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	1,285	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
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
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
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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	1,285	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	617	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	532	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	686	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
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
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
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
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
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
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	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
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
Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,555	1,562
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	430	297
Mark-to-market derivative liabilities (current liabilities)	392	262
Derivative Liability, Noncurrent	190	205
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	1	2
Derivative Asset, Notional Amount	2,049	1,043
Margin Deposit Assets	(148)	(209)
Derivative, Notional Amount	158	104
Unrealized Gain (Loss) on Investments	95	186
Exelon Generation Co L L C [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	608	171
Exelon Generation Co L L C [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	29	20
Exelon Generation Co L L C [Member] \| Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	104	181
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	125	124
DPP consideration	401	639
Assets, Fair Value Disclosure	16,855	16,992
Deferred Compensation Liability, Current and Noncurrent	(43)	(42)
Total Liabilities	(620)	(506)
Fair Value, Net Asset (Liability)	16,235	16,486
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	(577)	(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	(3,651)	(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	(14)	(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	3,088	3,525
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	15,031	14,780
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	604	305
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	177	195
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	4,828	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	1,306	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	2,071	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	51	56
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	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	1,360	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	813	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	532	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	686	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	64	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
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	31	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
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	29	28
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	1,057	1,193
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	3,966	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	33	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	(2,942)	(3,109)
Exelon Generation Co L L C [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7,568	7,525
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	(104)	(67)
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	125	124
DPP consideration	0	0
Assets, Fair Value Disclosure	7,477	6,457
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(107)	(142)
Fair Value, Net Asset (Liability)	7,370	6,315
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	(107)	(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	(359)	(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
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	252	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	7,018	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	509	210
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	177	195
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	2,070	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
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	2,030	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
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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	40	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
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
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
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	35	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
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	31	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
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
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	122	138
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	478	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
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	(356)	(607)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,439	3,886
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	145	321
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
DPP consideration	401	639
Assets, Fair Value Disclosure	3,666	4,982
Deferred Compensation Liability, Current and Noncurrent	(43)	(42)
Total Liabilities	(162)	(73)
Fair Value, Net Asset (Liability)	3,504	4,909
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	(119)	(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	(1,642)	(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	(9)	(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	1,532	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	2,859	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	95	95
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
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	1,190	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	1,023	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	41	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	51	56
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	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	35	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
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
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
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	29	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
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
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
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	29	28
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	377	334
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,748	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	16	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	(1,387)	(1,597)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,574	2,077
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	105	162
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
DPP consideration	0	0
Assets, Fair Value Disclosure	1,037	1,218
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(351)	(291)
Fair Value, Net Asset (Liability)	686	927
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	(351)	(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	(1,650)	(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	(5)	(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	1,304	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	479	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
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
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	283	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	283	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
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
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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
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	196	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
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
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
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
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
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
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
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	558	721
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,740	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	17	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	(1,199)	(905)
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Recurring [Member] \| Equity Securities Nuclear Decommissioning Trust Fund
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
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
DPP consideration	0	0
Assets, Fair Value Disclosure	4,675	4,335
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	4,675	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
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
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
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
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	4,675	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
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
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	1,285	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
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
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
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 [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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	1,285	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	617	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	532	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	686	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
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
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
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
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
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
Exelon Generation Co L L C [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Fair Value, Recurring [Member] \| Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	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
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
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
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,555	1,562
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	31	33
Derivative Liability, Noncurrent	264	268
Commonwealth Edison Co [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	59	83
Commonwealth Edison Co [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	40	37
Commonwealth Edison Co [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	43	43
Commonwealth Edison Co [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	300	285
Assets, Fair Value Disclosure	300	285
Total mark-to-market derivative liabilities	(295)	(301)
Deferred Compensation Liability, Current and Noncurrent	(8)	(8)
Total Liabilities	(303)	(309)
Fair Value, Net Asset (Liability)	(3)	(24)
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
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
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
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	300	285
Assets, Fair Value Disclosure	300	285
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	300	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
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
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
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
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(8)	(8)
Total Liabilities	(8)	(8)
Fair Value, Net Asset (Liability)	(8)	(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
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
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
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
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	(295)	(301)
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(295)	(301)
Fair Value, Net Asset (Liability)	(295)	(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
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
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
PECO Energy Co [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	48	18
PECO Energy Co [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	7	8
Assets, Fair Value Disclosure	29	30
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(9)	(9)
Total Liabilities	(9)	(9)
Fair Value, Net Asset (Liability)	20	21
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	22	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	9	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	13	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	7	8
Assets, Fair Value Disclosure	16	17
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	16	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	9	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	9	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
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
Assets, Fair Value Disclosure	13	13
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(9)	(9)
Total Liabilities	(9)	(9)
Fair Value, Net Asset (Liability)	4	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	13	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
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	13	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
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
Baltimore Gas and Electric Company [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	21	24
Baltimore Gas and Electric Company [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1	1
Baltimore Gas and Electric Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	120
Assets, Fair Value Disclosure	11	130
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(6)	(5)
Total Liabilities	(6)	(5)
Fair Value, Net Asset (Liability)	5	125
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	11	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	11	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
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	0	120
Assets, Fair Value Disclosure	11	130
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	11	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	11	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	11	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
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
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(6)	(5)
Total Liabilities	(6)	(5)
Fair Value, Net Asset (Liability)	(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
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
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
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
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
Pepco Holdings LLC [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	72	74
Pepco Holdings LLC [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5	0
Pepco Holdings LLC [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	9	10
Pepco Holdings LLC [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	527	86
Assets, Fair Value Disclosure	666	226
Deferred Compensation Liability, Current and Noncurrent	(16)	(17)
Total Liabilities	(16)	(17)
Fair Value, Net Asset (Liability)	650	209
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	139	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	53	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	15	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	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	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	527	86
Assets, Fair Value Disclosure	595	155
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	595	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	68	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	53	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	15	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
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
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
Assets, Fair Value Disclosure	36	37
Deferred Compensation Liability, Current and Noncurrent	(16)	(17)
Total Liabilities	(16)	(17)
Fair Value, Net Asset (Liability)	20	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	36	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
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
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	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	26	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
Assets, Fair Value Disclosure	35	34
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	35	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	35	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
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
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
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	35	34
Potomac Electric Power Company [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	34	30
Potomac Electric Power Company [Member] \| Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5	0
Potomac Electric Power Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	128	35
Assets, Fair Value Disclosure	244	150
Deferred Compensation Liability, Current and Noncurrent	(2)	(2)
Total Liabilities	(2)	(2)
Fair Value, Net Asset (Liability)	242	148
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	116	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	53	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	2	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	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	128	35
Assets, Fair Value Disclosure	181	88
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	181	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	53	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	53	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
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
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
Assets, Fair Value Disclosure	28	28
Deferred Compensation Liability, Current and Noncurrent	(2)	(2)
Total Liabilities	(2)	(2)
Fair Value, Net Asset (Liability)	26	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	28	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
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	2	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	26	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
Assets, Fair Value Disclosure	35	34
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	35	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	35	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
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
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	35	34
Delmarva Power and Light Company [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	14	15
Delmarva Power and Light Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	50	0
Assets, Fair Value Disclosure	50	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	50	0
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
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
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
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
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	50	0
Assets, Fair Value Disclosure	50	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	50	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
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
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
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
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
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
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
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
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
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
Atlantic City Electric Company [Member] \| Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	17	17
Atlantic City Electric Company [Member] \| Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	9	10
Atlantic City Electric Company [Member] \| Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	349	13
Assets, Fair Value Disclosure	349	13
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	349	13
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
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
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
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
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	349	13
Assets, Fair Value Disclosure	349	13
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	349	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
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
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
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
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
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
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
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
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	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
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
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
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
Exelon Generation Co LLC Affiliate [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	(58)	(62)
Maturity Less than 30 Days [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	108	116
Maturity Less than 30 Days [Member] \| Exelon Generation Co L L C [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	$ 108	$ 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
	Mar. 31, 2021	Mar. 31, 2020
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 660	$ 1,068
Total realized / unrealized gains (losses)
Included in net income	(276)	10
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	7	(14)
Change in collateral	(57)	1
Purchases, sales, issuances and settlements
Purchases	109	42
Sales	1	(22)
Settlements	(20)	(14)
Transfers into Level 3		2
Transfers out of Level 3	2	15
Ending Balance	426	1,088
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(147)	187
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
Total realized / unrealized gains (losses)
Included in net income	0	0
Included in noncurrent payables to affiliates	(1)	1
Included in regulatory assets	1	(1)
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3		0
Transfers out of Level 3	0	0
Ending Balance	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	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	129	177
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	927	1,328
Total realized / unrealized gains (losses)
Included in net income	(277)	9
Included in noncurrent payables to affiliates	1	(1)
Included in regulatory assets	0	0
Change in collateral	(57)	1
Purchases, sales, issuances and settlements
Purchases	109	42
Sales	1	(22)
Settlements	(20)	(14)
Transfers into Level 3		2
Transfers out of Level 3	2	15
Ending Balance	686	1,360
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(148)	186
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	497	511
Total realized / unrealized gains (losses)
Included in net income	1	(1)
Included in noncurrent payables to affiliates	1	(1)
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	3
Sales	0	0
Settlements	(20)	(14)
Transfers into Level 3		0
Transfers out of Level 3	0	0
Ending Balance	479	498
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	(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	430	817
Total realized / unrealized gains (losses)
Included in net income	(278)	10
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	0	0
Change in collateral	(57)	1
Purchases, sales, issuances and settlements
Purchases	109	39
Sales	1	(22)
Settlements	0	0
Transfers into Level 3		2
Transfers out of Level 3	2	15
Ending Balance	207	862
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(149)	187
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)	8	10
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	(301)	(301)
Total realized / unrealized gains (losses)
Included in net income	0	0
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	6	(13)
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3		0
Transfers out of Level 3	0	0
Ending Balance	(295)	(314)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	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)	(2)	(23)
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	41
Total realized / unrealized gains (losses)
Included in net income	1	1
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3		0
Transfers out of Level 3	0	0
Ending Balance	35	42
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	41
Total realized / unrealized gains (losses)
Included in net income	1	1
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3		0
Transfers out of Level 3	0	0
Ending Balance	35	42
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 1	$ 1

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
	Mar. 31, 2021	Mar. 31, 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	$ 276	$ (10)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(147)	187
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	(116)	72
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(65)	205
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	(162)	(62)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(84)	(18)
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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	1	(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	(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	277	(9)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(148)	186
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	(116)	72
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(65)	205
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	(162)	(62)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(84)	(18)
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	1	(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	(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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 1	$ 1

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ 105,000,000	$ 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	90,000,000	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	$ (295,000,000)	$ (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	1.35	2.25
Forward gas price assets	1.42	1.57
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Forward heat rate	800.00%	800.00%
Fair Value Inputs Renewable Factor	90.00%	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	235	163
Forward gas price assets	8.18	7.88
Derivative Asset (Liability) Net, Measurement Input	0.08	0.08
Forward heat rate	900.00%	900.00%
Fair Value Inputs Renewable Factor	123.00%	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	32	30
Forward gas price assets	2.59	2.59
Derivative Asset (Liability) Net, Measurement Input	0.0493	0.0493
Forward heat rate	885.00%	885.00%
Fair Value Inputs Renewable Factor	99.00%	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	0.11	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	1.16	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	0.27	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	$ 12,000,000	$ 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	9	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	102	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	30	27
Exelon Generation Co L L C [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 430,000,000	$ 297,000,000
Exelon Generation Co L L C [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	105,000,000	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	$ 90,000,000	$ 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	1.35	2.25
Forward gas price assets	1.42	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	235	163
Forward gas price assets	8.18	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	32	30
Forward gas price assets	2.59	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	0.11	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	1.16	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	0.27	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	$ 12,000,000	$ 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	9	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	102	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	30	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	$ (295,000,000)	$ (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	800.00%	800.00%
Fair Value Inputs Renewable Factor	90.00%	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	0.08	0.08
Forward heat rate	900.00%	900.00%
Fair Value Inputs Renewable Factor	123.00%	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	0.0493	0.0493
Forward heat rate	885.00%	885.00%
Fair Value Inputs Renewable Factor	99.00%	99.00%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Mar. 23, 2016USD ($)MW	Mar. 31, 2021USD ($)MGPSiteOpen_claimMW	Mar. 31, 2020MW	Sep. 30, 2018MW	Dec. 31, 2022MW	Dec. 31, 2020USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 3,123
Accrual for Environmental Loss Contingencies, Gross		473				$ 483
Liability for Asbestos and Environmental Claims, Gross		88				89
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		2,555
Accrual for Environmental Loss Contingencies, Gross		119				121
Liability for Asbestos and Environmental Claims, Gross		88				89
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		$ 281				293
Deferred Prosecution Agreement Payments						200
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 180
Mgp Site Contingency Monitoring Count \| MGPSite		8
Accrual for Environmental Loss Contingencies, Gross		$ 23				23
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 6
Mgp Site Contingency Monitoring Count \| MGPSite		4
Accrual for Environmental Loss Contingencies, Gross		$ 6				2
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		52
Accrual for Environmental Loss Contingencies, Gross		44				44
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		24
Accrual for Environmental Loss Contingencies, Gross		42				42
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 17
Mgp Site Contingency 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		$ 24
Open Asbestos Related Personal Injury Claims \| Open_claim		243
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		$ 64
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]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		280
West Lake [Member] \| Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		30
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		27
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
Subsequent Event [Member] \| Wind Assets [Member] \| Pepco Holdings Inc [Member] \| Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment \| MW					40

Commitments and Contingencies_3

Commitments and Contingencies - Merger Commitment (Details) $ in Millions	Mar. 31, 2021USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,123
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	52
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	24
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	17
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Pepco Holdings Inc [Member]
Other Commitments [Line Items]
Other Commitment	513
Pepco Holdings Inc [Member] \| Remaining commitment
Other Commitments [Line Items]
Other Commitment	79
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	64
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	53
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	Mar. 31, 2021USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,123
Other Commitment, to be Paid, Remainder of Fiscal Year	2,075
Other Commitment, to be Paid, Year Two	644
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	389
Guarantor Obligations, Maximum Exposure, Undiscounted	73
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,639
Other Commitment, to be Paid, Remainder of Fiscal Year	1,156
Other Commitment, to be Paid, Year Two	483
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	1,077
Other Commitment, to be Paid, Remainder of Fiscal Year	919
Other Commitment, to be Paid, Year Two	158
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	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 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	0
Other Commitment, to be Paid, after Year Five	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	29
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	11
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,555
Other Commitment, to be Paid, Remainder of Fiscal Year	1,935
Other Commitment, to be Paid, Year Two	620
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Exelon Generation Co L L C [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,623
Other Commitment, to be Paid, Remainder of Fiscal Year	1,141
Other Commitment, to be Paid, Year Two	482
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Exelon Generation Co L L C [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	932
Other Commitment, to be Paid, Remainder of Fiscal Year	794
Other Commitment, to be Paid, Year Two	138
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	224
Other Commitment, to be Paid, Remainder of Fiscal Year	21
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	200
Commonwealth Edison Co [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	7
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	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	14
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	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 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	0
Other Commitment, to be Paid, after Year Five	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	180
Other Commitment, to be Paid, Remainder of Fiscal Year	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	0
Other Commitment, to be Paid, after Year Five	178
PECO Energy Co [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	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	0
Other Commitment, to be Paid, after Year Five	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 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	0
Other Commitment, to be Paid, after Year Five	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	6
Other Commitment, to be Paid, Remainder of Fiscal Year	5
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Baltimore Gas and Electric Company [Member] \| Letters of Credit
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	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	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	0
Other Commitment, to be Paid, after Year Five	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	52
Other Commitment, to be Paid, Remainder of Fiscal Year	20
Other Commitment, to be Paid, Year Two	6
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	11
Guarantor Obligations, Maximum Exposure, Undiscounted	73
Pepco Holdings LLC [Member] \| Surety Bonds
Other Commitments [Line Items]
Other Commitment	23
Other Commitment, to be Paid, Remainder of Fiscal Year	20
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Pepco Holdings LLC [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	29
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	11
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	24
Other Commitment, to be Paid, Remainder of Fiscal Year	14
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	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	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	0
Other Commitment, to be Paid, after Year Five	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 Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	4
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Guarantor Obligations, Maximum Exposure, Undiscounted	30
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 Two	3
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Delmarva Power and Light Company [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	12
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Other Commitment, to be Paid, Remainder of Fiscal Year	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	1
Other Commitment, to be Paid, after Year Five	3
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	4
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	0
Other Commitment, to be Paid, after Year Five	0
Atlantic City Electric Company [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	0
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	1
Other Commitment, to be Paid, after Year Five	$ 3
Maximum [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years
Minimum [Member] \| Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	$ 473	$ 483
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	119	121
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	281	293
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	23	23
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	6	2
Pepco Holdings LLC [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	44	44
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	42	42
Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	1	1
Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	1	1
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	306	314
Accrual For MGP Investigation And Remediation [Member] \| Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] \| Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	280	293
Accrual For MGP Investigation And Remediation [Member] \| PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	21	21
Accrual For MGP Investigation And Remediation [Member] \| Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	5	0
Accrual For MGP Investigation And Remediation [Member] \| Pepco Holdings LLC [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] \| Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] \| Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] \| Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [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
	Mar. 31, 2021	Mar. 31, 2020
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 34,868	$ 34,573
Other comprehensive income	54	21
Ending balance	34,313	34,616
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(5)	(2)
OCI before reclassifications	0	(1)
Amounts reclassified from AOCI	0	0
Other comprehensive income	0	(1)
Ending balance	(5)	(3)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,372)	(3,165)
OCI before reclassifications	(2)	(7)
Amounts reclassified from AOCI	55	37
Other comprehensive income	53	30
Ending balance	(3,319)	(3,135)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(23)	(27)
OCI before reclassifications	1	(8)
Amounts reclassified from AOCI	0	0
Other comprehensive income	1	(8)
Ending balance	(22)	(35)
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,400)	(3,194)
OCI before reclassifications	(1)	(16)
Amounts reclassified from AOCI	55	37
Other comprehensive income	54	21
Ending balance	$ (3,346)	$ (3,173)

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
	Mar. 31, 2021	Mar. 31, 2020
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 1	$ 4
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(19)	(17)
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 0	$ 3

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 73
Distributed Energy Company
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%
Exelon Generation Co L L C [Member] \| Distributed Energy Company
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%
CENG [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%
Equity Method Investment, Ownership Percentage	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
CENG [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%
Guarantor Obligations, Current Carrying Value	$ 688
Equity Method Investment, Ownership Percentage	50.01%	50.01%
EGRP [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	51.00%	51.00%
EGRP [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	51.00%	51.00%
EGRP [Member] \| Exelon Generation Co L L C [Member] \| Wind project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%
EGRP [Member] \| Exelon Generation Co L L C [Member] \| Solar project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%
Antelope Valley [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%	100.00%
Antelope Valley [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%	100.00%
Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	31.00%	31.00%
Distributed Energy Company \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	31.00%	31.00%
NER
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	100.00%	100.00%
NER \| Exelon Generation Co L L C [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		Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,908	$ 663	$ 1,457	$ 587
Restricted cash and cash equivalents		374	438	414	358
Accounts receivable, net
Customer		3,575	3,231
Unamortized energy contract assets		38	38
Inventory, net
Materials and supplies		1,427	1,425
Assets held for sale		11	958
Other current assets		1,687	1,609
Total current assets		12,997	12,562
Property, plant and equipment, net		82,588	82,584
NDT funds		14,688	14,464
Unamortized energy contract assets		285	294
Other Assets, Noncurrent		3,033	2,982
Total assets	[1]	130,000	129,317
Long-term debt due within one year		2,281	1,819
Accounts payable		3,430	3,562
Accrued expenses		1,729	2,078
Unamortized energy contract liabilities		98	100
Liabilities held for sale		3	375
Other		1,176	1,264
Total current liabilities		13,580	12,771
Long-term debt		36,248	35,093
Asset retirement obligations, noncurrent		12,405	12,300
Unamortized energy contract liabilities		217	238
Other		2,988	2,942
Total liabilities	[1]	95,687	94,449
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		175	98
Restricted cash and cash equivalents		37	47
Accounts receivable, net
Customer		145	148
Other		35	36
Unamortized energy contract assets		22	22
Inventory, net
Materials and supplies		242	244
Assets held for sale		0	101
Other current assets		448	674
Total current assets		1,104	1,370
Property, plant and equipment, net		5,747	5,803
NDT funds		3,089	3,007
Unamortized energy contract assets		243	249
Other Assets, Noncurrent		47	52
Total noncurrent assets		9,126	9,111
Total assets		10,230	10,481
Long-term debt due within one year		90	94
Accounts payable		95	81
Accrued expenses		67	70
Unamortized energy contract liabilities		3	4
Liabilities held for sale		0	16
Other		1	5
Total current liabilities		256	270
Long-term debt		861	889
Asset retirement obligations, noncurrent		2,347	2,318
Other		116	129
Total noncurrent liabilities		3,324	3,336
Total liabilities		3,580	3,606
PP&E - unrestricted asset		1	1
Other Assets		0	9
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Unamortized energy contract assets		222
Recourse [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Total liabilities		2	8
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		721	226	821	303
Restricted cash and cash equivalents		41	89	150	146
Accounts receivable, net
Customer		1,792	1,298
Unamortized energy contract assets		38	38
Inventory, net
Materials and supplies		973	978
Assets held for sale		11	958
Other current assets		1,290	1,357
Total current assets		6,740	6,947
Property, plant and equipment, net		21,311	22,214
NDT funds		14,688	14,464
Unamortized energy contract assets		285	293
Other Assets, Noncurrent		1,835	1,826
Total assets	[2]	47,326	48,094
Long-term debt due within one year		699	197
Accounts payable		1,529	1,253
Accrued expenses		692	788
Unamortized energy contract liabilities		5	7
Liabilities held for sale		3	375
Other		371	444
Total current liabilities		6,298	5,219
Long-term debt		5,038	5,566
Asset retirement obligations, noncurrent		12,157	12,054
Unamortized energy contract liabilities		3	3
Other		1,405	1,308
Total liabilities	[2]	33,886	33,418
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		175	98
Restricted cash and cash equivalents		33	44
Accounts receivable, net
Customer		145	148
Other		35	36
Unamortized energy contract assets		22	22
Inventory, net
Materials and supplies		242	244
Assets held for sale		0	101
Other current assets		443	669
Total current assets		1,095	1,362
Property, plant and equipment, net		5,747	5,803
NDT funds		3,089	3,007
Unamortized energy contract assets		243	249
Other Assets, Noncurrent		38	42
Total noncurrent assets		9,117	9,101
Total assets		10,212	10,463
Long-term debt due within one year		69	68
Accounts payable		95	81
Accrued expenses		67	70
Unamortized energy contract liabilities		3	4
Liabilities held for sale		0	16
Other		1	5
Total current liabilities		235	244
Long-term debt		861	889
Asset retirement obligations, noncurrent		2,347	2,318
Other		116	129
Total noncurrent liabilities		3,324	3,336
Total liabilities		3,559	3,580
PP&E - unrestricted asset		1	1
Other Assets		0	9
Exelon Generation Co L L C [Member] \| Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Unamortized energy contract assets		222
Exelon Generation Co L L C [Member] \| Recourse [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Inventory, net
Total liabilities		2	8
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		558	111	49	131
Restricted cash and cash equivalents		37	39	37	36
Accounts receivable, net
Customer		456	525
Inventory, net
Materials and supplies		196	198
Other current assets		52	45
Total current assets		1,976	1,599
Property, plant and equipment, net		15,651	15,377
Other Assets, Noncurrent		310	307
Total assets	[3]	24,387	23,736
Long-term debt due within one year		304	347
Accounts payable		503	539
Accrued expenses		279	299
Unamortized energy contract liabilities		92	92
Other		137	141
Total current liabilities		1,643	2,154
Long-term debt		7,273	6,659
Asset retirement obligations, noncurrent		59	59
Unamortized energy contract liabilities		214	235
Other		595	622
Total liabilities	[3]	13,736	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		4	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		5	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
Total noncurrent assets		9	10
Total assets		18	18
Long-term debt due within one year		21	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		21	26
Long-term debt		0	0
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total noncurrent liabilities		0	0
Total liabilities		21	26
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		353	17	8	12
Restricted cash and cash equivalents		4	3	$ 3	$ 2
Accounts receivable, net
Customer		111	124
Inventory, net
Other current assets		2	3
Total current assets		631	326
Property, plant and equipment, net		3,552	3,475
Other Assets, Noncurrent		50	50
Total assets	[4]	4,679	4,286
Long-term debt due within one year		218	261
Accounts payable		162	177
Accrued expenses		48	46
Other		9	11
Total current liabilities		526	780
Long-term debt		1,500	1,152
Other		48	48
Total liabilities	[4]	2,985	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		4	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		4	3
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract assets		0	0
Other Assets, Noncurrent		9	10
Total noncurrent assets		9	10
Total assets		13	13
Long-term debt due within one year		16	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		16	21
Long-term debt		0	0
Asset retirement obligations, noncurrent		0	0
Other		0	0
Total noncurrent liabilities		0	0
Total liabilities		$ 16	$ 21

[1]	Exelon’s consolidated assets include $9,985 million and $10,200 million at March 31, 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 $3,578 million and $3,598 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,967 million and $10,182 million at March 31, 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 $3,557 million and $3,572 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $18 million at both March 31, 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 $21 million and $26 million at March 31, 2021 and December 31, 2020, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $13 million at both March 31, 2021 and December 31, 2020, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $16 million and $21 million at March 31, 2021 and December 31, 2020, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 16 — Variable Interest Entities for additional information.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Total assets	[1]	$ 130,000	$ 129,317
Total liabilities	[1]	95,687	94,449
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,175	1,178
Total liabilities		313	284
Exelon's ownership interest in VIE		150	157
Other ownership interests in VIE		712	737
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	[2]	47,326	48,094
Total liabilities	[2]	33,886	33,418
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,175	1,178
Total liabilities		313	284
Exelon's ownership interest in VIE		150	157
Other ownership interests in VIE		712	737
Commercial Agreement VIE [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		789	777
Total liabilities		95	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		694	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		789	777
Total liabilities		95	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		694	716
Equity Investment VIE [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		386	401
Total liabilities		218	223
Exelon's ownership interest in VIE		150	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		386	401
Total liabilities		218	223
Exelon's ownership interest in VIE		150	157
Other ownership interests in VIE		$ 18	$ 21

[1]	Exelon’s consolidated assets include $9,985 million and $10,200 million at March 31, 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 $3,578 million and $3,598 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,967 million and $10,182 million at March 31, 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 $3,557 million and $3,572 million at March 31, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.

Supplemental Financial Inform_3

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Statement of Operations Information [Line Items]
Operating lease income	$ 4	$ 5
Variable lease income	64	69
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	291	47
Net realized income on NDT funds - Non-regulatory agreement units	203	82
Net unrealized gains on NDT funds - Regulatory agreement units	(82)	(932)
Net unrealized gains on NDT funds - Non-regulatory agreement units	(66)	(706)
Regulatory offset to NDT fund-related activities	(167)	709
Decommissioning-related activities	179	(800)
AFUDC - Equity	28	23
Non-service net periodic benefit cost	20	10
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	3	3
Variable lease income	64	69
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	291	47
Net realized income on NDT funds - Non-regulatory agreement units	203	82
Net unrealized gains on NDT funds - Regulatory agreement units	(82)	(932)
Net unrealized gains on NDT funds - Non-regulatory agreement units	(66)	(706)
Regulatory offset to NDT fund-related activities	(167)	709
Decommissioning-related activities	179	(800)
AFUDC - Equity	0	0
Non-service net periodic benefit cost	0	0
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	4	6
Non-service net periodic benefit cost	0	0
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	6	3
Non-service net periodic benefit cost	0	0
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	7	5
Non-service net periodic benefit cost	0	0
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	1	1
Variable lease income	0	0
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	11	9
Non-service net periodic benefit cost	0	0
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	9	6
Non-service net periodic benefit cost	0	0
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating lease income	1	1
Variable lease income	0	0
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	1	1
Non-service net periodic benefit cost	0	0
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	0	0
Net realized income on NDT funds - Non-regulatory agreement units	0	0
Net unrealized gains on NDT funds - Regulatory agreement units	0	0
Net unrealized gains on NDT funds - Non-regulatory agreement units	0	0
Regulatory offset to NDT fund-related activities	0	0
Decommissioning-related activities	0	0
AFUDC - Equity	1	2
Non-service net periodic benefit cost	$ 0	$ 0

Supplemental Financial Inform_4

Supplemental Financial Information - Taxes Other Than Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Statement of Operations Information [Line Items]
Utility taxes	$ 217	$ 218
Property	154	150
Payroll	61	63
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	24	26
Property	68	69
Payroll	28	31
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	59	60
Property	8	7
Payroll	7	7
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	35	31
Property	4	4
Payroll	4	4
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	25	26
Property	42	39
Payroll	5	4
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	74	75
Property	32	31
Payroll	7	8
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	67	69
Property	21	21
Payroll	2	2
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	6	6
Property	10	9
Payroll	1	1
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	1	0
Property	1	1
Payroll	$ 0	$ 1

Supplemental Financial Inform_5

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	$ 1,522	$ 856
Amortization of regulatory assets	160	149
Amortization of intangible assets, net	15	16
Amortization of energy contract assets and liabilities	4	2
Nuclear fuel	276	231
ARO accretion	127	124
Total depreciation, amortization and accretion	2,104	1,378
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	95	98
Allowance for credit losses	85	45
Other decommissioning-related activity	(322)	128
Energy-related options	17	6
True-up adjustments to decoupling mechanisms and formula rates	(129)	(71)
Long-term incentive plan	32	(7)
Amortization of operating ROU asset	37	51
AFUDC - Equity	28	23
Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(28)	(23)
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	928	290
Amortization of regulatory assets	0	0
Amortization of intangible assets, net	12	14
Amortization of energy contract assets and liabilities	3	2
Nuclear fuel	276	231
ARO accretion	127	124
Total depreciation, amortization and accretion	1,346	661
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	26	27
Allowance for credit losses	34	4
Other decommissioning-related activity	(332)	128
Energy-related options	17	6
True-up adjustments to decoupling mechanisms and formula rates	0	0
Long-term incentive plan	0	0
Amortization of operating ROU asset	21	35
AFUDC - Equity	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	239	228
Amortization of regulatory assets	53	45
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	292	273
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	32	28
Allowance for credit losses	13	7
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(54)	(17)
Long-term incentive plan	0	0
Amortization of operating ROU asset	0	0
AFUDC - Equity	4	6
Commonwealth Edison Co [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(4)	(6)
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	82	79
Amortization of regulatory assets	4	7
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	86	86
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	2	1
Allowance for credit losses	24	17
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(10)	0
Long-term incentive plan	0	0
Amortization of operating ROU asset	0	0
AFUDC - Equity	6	3
PECO Energy Co [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(6)	(3)
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	106	97
Amortization of regulatory assets	46	46
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	152	143
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	14	15
Allowance for credit losses	4	7
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(18)	(35)
Long-term incentive plan	0	0
Amortization of operating ROU asset	7	8
AFUDC - Equity	7	5
Baltimore Gas and Electric Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(7)	(5)
Pepco Holdings LLC [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	154	144
Amortization of regulatory assets	56	50
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	210	194
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	12	17
Allowance for credit losses	10	10
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(46)	(19)
Long-term incentive plan	0	0
Amortization of operating ROU asset	7	5
AFUDC - Equity	11	9
Pepco Holdings LLC [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(11)	(9)
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	67	64
Amortization of regulatory assets	35	31
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	102	95
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	2	3
Allowance for credit losses	5	4
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(26)	(15)
Long-term incentive plan	0	0
Amortization of operating ROU asset	1	2
AFUDC - Equity	9	6
Potomac Electric Power Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(9)	(6)
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	42	38
Amortization of regulatory assets	11	10
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	53	48
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	1	1
Allowance for credit losses	4	3
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(9)	(4)
Long-term incentive plan	0	0
Amortization of operating ROU asset	3	2
AFUDC - Equity	1	1
Delmarva Power and Light Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	(1)	(1)
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	37	34
Amortization of regulatory assets	10	9
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	47	43
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	3	3
Allowance for credit losses	1	3
Other decommissioning-related activity	0	0
Energy-related options	0	0
True-up adjustments to decoupling mechanisms and formula rates	(11)	0
Long-term incentive plan	0	0
Amortization of operating ROU asset	1	1
AFUDC - Equity	1	2
Atlantic City Electric Company [Member] \| Return on borrowed funds
Other Non-Cash Operating Activities [Abstract]
AFUDC - Equity	$ (1)	$ (2)

Supplemental Financial Inform_6

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 1,908	$ 663	$ 1,457	$ 587
Restricted cash	374	438	414	358
Restricted cash included in other long-term assets	52	53	121	177
Total cash, restricted cash, and cash equivalents	2,334	1,166	1,992	1,122
Accrued Expenses [Abstract]
Compensation-related accruals	581	1,069
Taxes accrued	540	527
Interest accrued	424	331
Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		12
Exelon Generation Co L L C [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	721	226	821	303
Restricted cash	41	89	150	146
Restricted cash included in other long-term assets	0	0	0	0
Total cash, restricted cash, and cash equivalents	762	327	971	449
Accrued Expenses [Abstract]
Compensation-related accruals	210	426
Taxes accrued	279	229
Interest accrued	76	44
Exelon Generation Co L L C [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		12
Commonwealth Edison Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	86	83	514	90
Restricted cash	270	279	211	150
Restricted cash included in other long-term assets	43	43	108	163
Total cash, restricted cash, and cash equivalents	399	405	833	403
Accrued Expenses [Abstract]
Compensation-related accruals	91	170
Taxes accrued	70	94
Interest accrued	65	109
Commonwealth Edison Co [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
PECO Energy Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	48	19	31	21
Restricted cash	7	7	7	6
Restricted cash included in other long-term assets	0	0	0	0
Total cash, restricted cash, and cash equivalents	55	26	38	27
Accrued Expenses [Abstract]
Compensation-related accruals	42	73
Taxes accrued	18	16
Interest accrued	36	37
PECO Energy Co [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
Baltimore Gas and Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	21	144	11	24
Restricted cash	1	1	1	1
Restricted cash included in other long-term assets	0	0	0	0
Total cash, restricted cash, and cash equivalents	22	145	12	25
Accrued Expenses [Abstract]
Compensation-related accruals	49	84
Taxes accrued	50	73
Interest accrued	41	46
Baltimore Gas and Electric Company [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
Pepco Holdings LLC [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	558	111	49	131
Restricted cash	37	39	37	36
Restricted cash included in other long-term assets	9	10	12	14
Total cash, restricted cash, and cash equivalents	604	160	98	181
Accrued Expenses [Abstract]
Compensation-related accruals	73	109
Taxes accrued	108	117
Interest accrued	79	51
Pepco Holdings LLC [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
Potomac Electric Power Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	134	30	18	30
Restricted cash	33	35	33	33
Restricted cash included in other long-term assets	0	0	0	0
Total cash, restricted cash, and cash equivalents	167	65	51	63
Accrued Expenses [Abstract]
Compensation-related accruals	26	36
Taxes accrued	92	90
Interest accrued	37	26
Potomac Electric Power Company [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
Delmarva Power and Light Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	64	15	7	13
Restricted cash	0	0	0	0
Restricted cash included in other long-term assets	0	0	0	0
Total cash, restricted cash, and cash equivalents	64	15	7	13
Accrued Expenses [Abstract]
Compensation-related accruals	15	18
Taxes accrued	10	18
Interest accrued	20	7
Delmarva Power and Light Company [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		0
Atlantic City Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	353	17	8	12
Restricted cash	4	3	3	2
Restricted cash included in other long-term assets	9	10	12	14
Total cash, restricted cash, and cash equivalents	366	30	$ 23	$ 28
Accrued Expenses [Abstract]
Compensation-related accruals	12	17
Taxes accrued	12	12
Interest accrued	$ 20	12
Atlantic City Electric Company [Member] \| Held for Sale
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Total cash, restricted cash, and cash equivalents		$ 0

Related Party Transactions - Op

Related Party Transactions - Operating Revenues and Purchased Power and Fuel (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Related Party Transaction [Line Items]
Revenue from Related Parties	$ 0	$ 1
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	295	330
Purchased power and/or fuel from affiliates	0	(6)
Exelon Generation Co L L C [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	78	90
Purchased power and/or fuel from affiliates	6	7
Exelon Generation Co L L C [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	42	37
Exelon Generation Co L L C [Member] \| Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	72	99
Exelon Generation Co L L C [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	100	103
Exelon Generation Co L L C [Member] \| Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	75	79
Exelon Generation Co L L C [Member] \| Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	21	22
Exelon Generation Co L L C [Member] \| Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	4	2
Exelon Generation Co L L C [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	3	1
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	6	5
Purchased power and/or fuel from affiliates	85	97
Commonwealth Edison Co [Member] \| Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Purchased power and/or fuel from affiliates	$ 84	$ 97

Related Party Transactions - BS

Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	$ 124	$ 113
PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	17	14
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	145	142
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	144	140
Related Party Transaction Capitalized Costs Support Services	10	11
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	71	74
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	72
Related Party Transaction Capitalized Costs Support Services	45	42
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	41	38
PECO Energy Co [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	39	37
Related Party Transaction Capitalized Costs Support Services	17	16
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	45	42
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	43	41
Related Party Transaction Capitalized Costs Support Services	20	28
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	40	38
Pepco Holdings LLC [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	39	37
Related Party Transaction Capitalized Costs Support Services	32	16
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
Related Party Transaction Capitalized Costs Support Services	17	14
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	52	51
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	22	21
Related Party Transaction Capitalized Costs Support Services	13	6
Potomac Electric Power Company [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	30	30
Related Party Transaction Capitalized Costs Support Services	7	6
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	39	37
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
Related Party Transaction Capitalized Costs Support Services	10	5
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	25	24
Related Party Transaction Capitalized Costs Support Services	5	4
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	34	33
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	12	11
Related Party Transaction Capitalized Costs Support Services	8	4
Atlantic City Electric Company [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	22	22
Related Party Transaction Capitalized Costs Support Services	$ 5	$ 4

Related Party Transactions - Cu

Related Party Transactions - Current Receivables From/Payables To Affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 441	$ 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	125	107
Accounts Receivable, Related Parties, Current	106	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	50	78
Due to Related Parties, Current	24	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	15	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	11	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	12	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	2	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	8	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	8	25
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	80	96
Accounts Receivable, Related Parties, Current	21	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	17	13
Accounts Payable, Related Parties, Current	26	28
Commonwealth Edison Co [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	104	146
Commonwealth Edison Co [Member] \| PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	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	1	0
Commonwealth Edison Co [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	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	1	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	1	5
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	46	50
Accounts Receivable, Related Parties, Current	0	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	0	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	43	61
Accounts Receivable, Related Parties, Current	0	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	0	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	0	2
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	78	104
Accounts Receivable, Related Parties, Current	0	8
Pepco Holdings LLC [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	18	15
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	44	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	0	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	0	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	27	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	84	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	24	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	30	47
Business Services Company [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	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	16	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	11	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	8	15
Business Services Company [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	35	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	14	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	10	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	10	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	24	22
Other Legal Entities [Member] \| Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	5	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	1	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	1	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	Mar. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 2,865	$ 3,017
Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	2,375	2,541
PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 490	$ 475

Related Party Transactions - Lo

Related Party Transactions - Long Term Debt to Financing Trusts (Details) - USD ($) $ in Millions	Mar. 31, 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