NiSource (NI) 10-K17 Feb 212020 FY Annual reportFinancial data

Company Profile

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2020	Feb. 09, 2021	Jun. 30, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-16189
Entity Registrant Name	NiSource Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	35-2108964
Entity Address, Address Line One	801 East 86th Avenue
Entity Address, City or Town	Merrillville,
Entity Address, State or Province	IN
Entity Address, Postal Zip Code	46410
City Area Code	(877)
Local Phone Number	647-5990
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 8,671,854,266
Entity Common Stock, Shares Outstanding		391,859,711
Entity Central Index Key	0001111711
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference [Text Block]	Part III of this report incorporates by reference specific portions of the Registrant’s Notice of Annual Meeting and Proxy Statement relating to the Annual Meeting of Stockholders to be held on May 25, 2021.
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	NI
Security Exchange Name	NYSE
Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th ownership interest in a share of 6.50% Series B
Trading Symbol	NI PR B
Security Exchange Name	NYSE

Statements Of Consolidated Inco

Statements Of Consolidated Income (Loss) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Revenues
Customer revenues	$ 4,473.2	$ 5,053.4	$ 4,991.1
Other revenues	208.5	155.5	123.4
Total Operating Revenues	4,681.7	5,208.9	5,114.5
Operating Expenses
Cost of energy	1,109.3	1,534.8	1,761.3
Operation and maintenance	1,585.9	1,354.7	2,352.9
Depreciation and amortization	725.9	717.4	599.6
Impairment of goodwill and intangible assets	0	414.5	0
Loss on sale of assets, net	410.6	0	1.2
Other taxes	299.2	296.8	274.8
Total Operating Expenses	4,130.9	4,318.2	4,989.8
Operating Income (Loss)	550.8	890.7	124.7
Other Income (Deductions)
Interest expense, net	(370.7)	(378.9)	(353.3)
Other, net	32.1	(5.2)	43.5
Loss on early extinguishment of long-term debt	(243.5)	0	(45.5)
Total Other Deductions, Net	(582.1)	(384.1)	(355.3)
Income (Loss) before Income Taxes	(31.3)	506.6	(230.6)
Income Taxes	(17.1)	123.5	(180)
Net Income (Loss)	(14.2)	383.1	(50.6)
Net Income (Loss) Attributable to Noncontrolling Interest	3.4	0	0
Net Income (Loss) Attributable to NiSource	(17.6)	383.1	(50.6)
Preferred dividends	(55.1)	(55.1)	(15)
Net Income (Loss) Available to Common Shareholders	$ (72.7)	$ 328	$ (65.6)
Earnings Per Share
Basic Earnings (Loss) Per Share	$ (0.19)	$ 0.88	$ (0.18)
Diluted Earnings (Loss) Per Share	$ (0.19)	$ 0.87	$ (0.18)
Basic Average Common Shares Outstanding	384,347	374,650	356,491
Diluted Average Common Shares	384,347	375,986	356,491

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Income (Loss)		$ (14.2)	$ 383.1	$ (50.6)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale securities	[1]	2.7	5.7	(2.6)
Net unrealized gain (loss) on cash flow hedges	[2]	(70.7)	(64.2)	22.7
Unrecognized pension and OPEB benefit (costs)	[3]	3.9	3.1	(4.4)
Total other comprehensive income (loss)		(64.1)	(55.4)	15.7
Total Comprehensive Income (Loss)		$ (78.3)	$ 327.7	$ (34.9)

[1]	Net unrealized gain (loss) on available-for-sale securities, net of $0.7 million tax expense, $1.5 million tax expense and $0.6 million tax benefit in 2020, 2019 and 2018, respectively.
[2]	Net unrealized gain (loss) on derivatives qualifying as cash flow hedges, net of $23.4 million tax benefit, $21.2 million tax benefit and $7.5 million tax expense in 2020, 2019 and 2018, respectively.
[3]	Unrecognized pension and OPEB benefit (costs), net of $0.1 million tax benefit, $1.6 million tax expense and $1.5 million tax benefit in 2020, 2019 and 2018, respectively.

Statements of Consolidated Co_2

Statements of Consolidated Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	$ 0.7	$ 1.5	$ (0.6)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(23.4)	(21.2)	7.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 0.1	$ (1.6)	$ 1.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
Plant		$ 24,179.9	$ 24,541.9
Accumulated depreciation and amortization		(7,560.4)	(7,629.7)
Net Property, Plant and Equipment	[1]	16,619.5	16,912.2
Investments and Other Assets
Unconsolidated affiliates		0	1.3
Available-for-sale debt securities (amortized cost of $163.9 and $150.1, allowance for credit losses of $0.5 and $0, respectively)		170.9	154.2
Other investments		81.1	74.7
Total Investments and Other Assets		252	230.2
Current Assets
Cash and cash equivalents		116.5	139.3
Restricted cash		9.1	9.1
Accounts receivable		843.6	876.1
Allowance for credit losses		(52.3)	(19.2)
Accounts receivable, net		791.3	856.9
Gas inventory		191.2	250.9
Materials and supplies, at average cost		141.5	120.2
Electric production fuel, at average cost		68.4	53.6
Exchange gas receivable		34.1	48.5
Regulatory assets		135.7	225.7
Deferred property taxes		85.6	79.5
Prepayments and other		86	70.2
Total Current Assets	[1]	1,659.4	1,853.9
Other Assets
Regulatory assets		1,794.8	2,013.9
Goodwill		1,485.9	1,485.9
Deferred charges and other		228.9	163.7
Total Other Assets		3,509.6	3,663.5
Total Assets		22,040.5	22,659.8
Stockholders' Equity
Common stock - $0.01 par value, 600,000,000 shares authorized; 391,760,051 and 382,135,680 shares outstanding, respectively		3.9	3.8
Preferred stock - $0.01 par value, 20,000,000 shares authorized; 440,000 shares outstanding		880	880
Treasury stock		(99.9)	(99.9)
Additional paid-in capital		6,890.1	6,666.2
Retained deficit		(1,765.2)	(1,370.8)
Accumulated other comprehensive loss		(156.7)	(92.6)
Total NiSource Stockholders' Equity		5,752.2	5,986.7
Noncontrolling interest in consolidated subsidiaries		85.6	0
Total Stockholders’ Equity		5,837.8	5,986.7
Long-term debt, excluding amounts due within one year		9,219.8	7,856.2
Total Capitalization		15,057.6	13,842.9
Current Liabilities
Current portion of long-term debt		23.3	13.4
Short-term borrowings		503	1,773.2
Accounts payable		589	666
Customer deposits and credits		243.3	256.4
Taxes accrued		244.1	231.6
Interest accrued		104.7	99.4
Risk management liabilities		78.2	12.6
Exchange gas payable		48.5	59.7
Regulatory liabilities		161.3	160.2
Accrued compensation and employee benefits		141.8	156.3
Claims accrued		28.6	165.4
Other accruals		113.6	151.6
Total Current Liabilities		2,279.4	3,745.8
Other Liabilities
Risk management liabilities		144.6	134
Deferred Income Tax Liabilities, Net		1,470.6	1,485.3
Accrued insurance liabilities		84.8	81.5
Accrued liability for postretirement and postemployment benefits		336.1	373.2
Regulatory liabilities		1,904.2	2,352
Asset retirement obligations		477.1	416.9
Other noncurrent liabilities		286.1	228.2
Total Other Liabilities		4,703.5	5,071.1
Total Capitalization and Liabilities		$ 22,040.5	$ 22,659.8

[1]	(1) Includes $175.6 million of net property, plant and equipment assets and $1.7 million of current assets of a consolidated VIE that may be used only to settle obligations of the consolidated VIE. Refer to Note 4 "Variable Interest Entity" for additional information.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2020USD ($)$ / sharesshares
Amortized Cost	$ 163.9
Allowance for Credit Loss	0.5
Net Property, Plant and Equipment	16,619.5	[1]
Current assets	$ 1,659.4	[1]
Common stock, par value \| $ / shares	$ 0.01
Common stock, shares authorized \| shares	600,000,000
Common stock, shares outstanding \| shares	391,760,051
Preferred Stock, Par or Stated Value Per Share \| $ / shares	$ 0.01
Preferred Stock, Shares Authorized \| shares	20,000,000
Preferred Stock, Shares Outstanding \| shares	440,000
Rosewater
Net Property, Plant and Equipment	$ 175.6
Current assets	$ 1.7

[1]	(1) Includes $175.6 million of net property, plant and equipment assets and $1.7 million of current assets of a consolidated VIE that may be used only to settle obligations of the consolidated VIE. Refer to Note 4 "Variable Interest Entity" for additional information.

Statements Of Consolidated Cash

Statements Of Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net Income (Loss)	$ (14.2)	$ 383.1	$ (50.6)
Adjustments to Reconcile Net Income (Loss) to Net Cash from Operating Activities:
Loss on early extinguishment of debt	243.5	0	45.5
Depreciation and amortization	725.9	717.4	599.6
Deferred income taxes and investment tax credits	(29)	118.2	(188.2)
Stock compensation expense and 401(k) profit sharing contribution	17.4	25.9	28.6
Impairment of goodwill and intangible assets	0	414.5	0
Loss (gain) on sale of assets	409.8	(0.6)	1.3
Amortization of discount/premium on debt	9.4	8.2	7.5
AFUDC equity	(9.9)	(8)	(14.2)
Other adjustments	0.2	(0.3)	0.4
Changes in Assets and Liabilities:
Accounts receivable	(3.9)	187.8	(186.2)
Inventories	(1.5)	(2)	41.4
Accounts payable	(29.7)	(299.9)	268.4
Customer deposits and credits	10	16.9	(25.4)
Taxes accrued	28.4	7.3	20.2
Interest accrued	5.3	8.8	(21.7)
Exchange gas receivable/payable	(6.9)	55.5	(21.5)
Other accruals	(218.8)	105.3	43.5
Prepayments and other current assets	(5.9)	(33.6)	(14.5)
Regulatory assets/liabilities	70.8	(85.6)	(53.2)
Postretirement and postemployment benefits	(103.6)	(21.1)	58.2
Deferred charges and other noncurrent assets	(15)	(76.1)	3.8
Other noncurrent liabilities	21.7	61.6	(2.8)
Net Cash Flows from Operating Activities	1,104	1,583.3	540.1
Investing Activities
Capital expenditures	(1,758.1)	(1,802.4)	(1,818.2)
Cost of removal	(138.2)	(113.2)	(104.3)
Proceeds from disposition of assets	1,115.9	0.4	1.8
Purchases of available-for-sale securities	(144.7)	(140.4)	(90)
Sales of available-for-sale securities	131.4	132.1	82.3
Payment to renewable generation asset developer	(85.3)	0	0
Other investing activities	(0.1)	1.1	2.3
Net Cash Flows used for Investing Activities	(879.1)	(1,922.4)	(1,926.1)
Financing Activities
Proceeds from issuance of long-term debt	2,974	750	350
Repayments of long-term debt and finance lease obligations	(1,622)	(51.6)	(1,046.1)
Issuance of short-term debt (maturity > 90 days)	1,350	600	950
Repayments of short-term debt (maturity 90 days)	(2,200)	(700)	0
Change in short-term borrowings, net (maturity ≤ 90 days)	(420.1)	(104)	(178.5)
Issuance of common stock, net of issuance costs	211.4	244.4	848.2
Issuance of preferred stock, net of issuance costs	0	0	880
Equity costs, premiums and other debt related costs	(246.5)	(17.8)	(46)
Acquisition of treasury stock	0	0	(4)
Contributions from non-controlling interest, net of issuance costs	82.2	0	0
Dividends paid - common stock	(321.6)	(298.5)	(273.3)
Dividends paid - preferred stock	(55.1)	(56.1)	(11.6)
Net Cash Flows from Financing Activities	(247.7)	366.4	1,468.7
Change in cash, cash equivalents and restricted cash	(22.8)	27.3	82.7
Cash, cash equivalents and restricted cash at beginning of period	148.4	121.1	38.4
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 125.6	$ 148.4	$ 121.1

Statements Of Consolidated Stoc

Statements Of Consolidated Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Preferred Stock	[1]	Treasury Stock	Additional Paid-in Capital	Retained Deficit	Retained DeficitCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive LossCumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interest
Beginning Balance at Dec. 31, 2017	$ 4,320.1	$ 3.4	$ 0		$ (95.9)	$ 5,529.1	$ (1,073.1)		$ (43.4)		$ 0
Comprehensive Income (Loss):
Net Income (Loss)	(50.6)	0	0		0	0	(50.6)		0		0
Other Comprehensive Income (Loss), Net of Tax	15.7	0	0		0	0	0		15.7		0
Dividends:
Common stock	(273.5)	0	0		0	0	(273.5)		0		0
Preferred stock	(11.6)	0	0		0	0	(11.6)		0		0
Treasury stock acquired	(4)	0	0		(4)	0	0		0		0
Stock issuances:
Common stock	599.6	0.3	0		0	599.3	0		0		0
Preferred Stock	880	0	880		0	0	0		0		0
Employee stock purchase plan	5.5	0	0		0	5.5	0		0		0
Long-term incentive plan	15.4	0	0		0	15.4	0		0		0
401(k) and profit sharing	21.8	0	0		0	21.8	0		0		0
ATM Program	232.5	0.1	0		0	232.4	0		0		0
Ending Balance at Dec. 31, 2018	5,750.9	3.8	880		(99.9)	6,403.5	(1,399.3)	$ (9.5)	(37.2)	$ 9.5	0
Comprehensive Income (Loss):
Net Income (Loss)	383.1	0	0		0	0	383.1		0		0
Other Comprehensive Income (Loss), Net of Tax	(55.4)	0	0		0	0	0		(55.4)		0
Dividends:
Common stock	(298.5)	0	0		0	0	(298.5)		0		0
Preferred stock	(56.1)	0	0		0	0	(56.1)		0		0
Stock issuances:
Employee stock purchase plan	5.6	0	0		0	5.6	0		0		0
Long-term incentive plan	10.4	0	0		0	10.4	0		0		0
401(k) and profit sharing	17.6	0	0		0	17.6	0		0		0
ATM Program	229.1	0	0		0	229.1	0		0		0
Ending Balance at Dec. 31, 2019	5,986.7	3.8	880		(99.9)	6,666.2	(1,370.8)		(92.6)		0
Comprehensive Income (Loss):
Net Income (Loss)	(14.2)	0	0		0	0	(17.6)		0		3.4
Other Comprehensive Income (Loss), Net of Tax	(64.1)	0	0		0	0	0		(64.1)		0
Dividends:
Common stock	(321.7)	0	0		0	0	(321.7)		0		0
Preferred stock	(55.1)	0	0		0	0	(55.1)		0		0
Contribution from noncontrolling interest	82.2	0	0		0	0	0		0		82.2
Stock issuances:
Employee stock purchase plan	5.7	0	0		0	5.7	0		0		0
Long-term incentive plan	8.4	0	0		0	8.4	0		0		0
401(k) and profit sharing	13.4	0	0		0	13.4	0		0		0
ATM Program	196.5	0.1	0		0	196.4	0		0		0
Ending Balance at Dec. 31, 2020	$ 5,837.8	$ 3.9	$ 880		$ (99.9)	$ 6,890.1	$ (1,765.2)		$ (156.7)		$ 85.6

[1]	Series A and Series B shares have an aggregate liquidation preference of $400M and $500M, respectively. See Note 13, "Equity" for additional information.

Statements Of Consolidated St_2

Statements Of Consolidated Stockholders' Equity (Shares) - shares shares in Thousands		Total	Common Stock	Treasury Stock	Preferred Stock
Beginning Balance at Dec. 31, 2017		337,016	340,813	3,797	0
Treasury stock acquired		(166)	0	(166)	0
Issued:
Common stock - private placement		24,964	24,964	0	0
Preferred stock		0	0	0	420
Employee stock purchase plan		223	223	0	0
Long-term incentive plan		561	561	0	0
401(k) and profit sharing plan		882	882	0	0
ATM Program		8,883	8,883	0	0
Ending Balance at Dec. 31, 2018		372,363	376,326	3,963	420
Issued:
Preferred stock	[1]	0	0	0	20
Employee stock purchase plan		201	201	0	0
Long-term incentive plan		518	518	0	0
401(k) and profit sharing plan		631	631	0	0
ATM Program		8,423	8,423	0	0
Ending Balance at Dec. 31, 2019		382,136	386,099	3,963	440
Issued:
Employee stock purchase plan		236	236	0	0
Long-term incentive plan		385	385	0	0
401(k) and profit sharing plan		544	544	0	0
ATM Program		8,459	8,459	0	0
Ending Balance at Dec. 31, 2020		391,760	395,723	3,963	440

[1]	See Note 13, "Equity," for additional information.

Statements of Consolidated St_3

Statements of Consolidated Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Stock, Dividends, Per Share, Declared	$ 0.84	$ 0.80	$ 0.78
Preferred Stock, Dividends Per Share, Declared			28.88
Series A Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 56.50	56.50	28.88
Preferred Stock, Liquidation Preference, Value	$ 400
Series B Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 1,625	$ 1,674.65	$ 0
Preferred Stock, Liquidation Preference, Value	$ 500

Nature of Operations And Summar

Nature of Operations And Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	Nature of Operations and Summary of Significant Accounting Policies A. Company Structure and Principles of Consolidation. We are an energy holding company incorporated in Delaware and headquartered in Merrillville, Indiana. Our subsidiaries are fully regulated natural gas and electric utility companies serving approximately 3.7 million customers in six states. We generate substantially all of our operating income through these rate-regulated businesses. The consolidated financial statements include the accounts of us, our majority-owned subsidiaries, and VIEs of which we are the primary beneficiary after the elimination of all intercompany accounts and transactions. On February 26, 2020, NiSource and Columbia of Massachusetts entered into an Asset Purchase Agreement with Eversource (the "Asset Purchase Agreement"). On October 9, 2020, NiSource and Columbia of Massachusetts received net proceeds from the sale of approximately $1,113 million, which included, a $1,100 million purchase price, an estimate of Columbia of Massachusetts' net working capital, net of closing costs and a $56.0 million payment in lieu of penalties that NiSource agreed to make in full settlement of all of the pending and potential claims, lawsuits, investigations or proceedings settled by and released by a settlement agreement approved by the Massachusetts DPU. As of December 31, 2020, we have recorded a loss on the sale of $412.4 million based on asset and liability balances as of the close of the transaction on October 9, 2020, estimated net working capital and estimated transaction costs. This estimated pre-tax loss is presented as "Loss on sale of assets, net" on the Statements of Consolidated Income (Loss) and is subject to change based on the final net working capital determination. The Massachusetts Business had the following pretax income (loss) for the twelve months ended December 31, 2020, 2019 and 2018: Twelve Months Ended (in millions) 2020 2019 2018 Pretax Income (Loss) ($422.3) $36.8 ($835.6) We continue to monitor how the COVID-19 pandemic is affecting our workforce, customers, suppliers, operations, financial results and cash flow. See Note 3, "Revenue Recognition," Note 9, "Regulatory Matters," and Note 11, "Income Taxes," for information on the pandemic. B. Use of Estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. C. Cash, Cash Equivalents and Restricted Cash. We consider all highly liquid investments with original maturities of three months or less to be cash equivalents. We report amounts deposited in brokerage accounts for margin requirements as restricted cash. In addition, we have amounts deposited in trust to satisfy requirements for the provision of various property, liability, workers compensation, and long-term disability insurance, which is classified as restricted cash on the Consolidated Balance Sheets and disclosed with cash and cash equivalents on the Statements of Consolidated Cash Flows. D. Accounts Receivable and Unbilled Revenue. Accounts receivable on the Consolidated Balance Sheets includes both billed and unbilled amounts. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the last cycle billing date through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates, weather and reasonable and supportable forecasts. Accounts receivable fluctuates from year to year depending in large part on weather impacts and price volatility. Our accounts receivable on the Consolidated Balance Sheets include unbilled revenue, less reserves, in the amounts of $338.3 million and $350.5 million as of December 31, 2020 and 2019, respectively. The reserve for uncollectible receivables is our best estimate of the amount of probable credit losses in the existing accounts receivable. We determined the reserve based on historical experience and in consideration of current market conditions. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered. Refer to Note 3, "Revenue Recognition," for additional information on customer-related accounts receivable. E. Investments in Debt Securities. Our investments in debt securities are carried at fair value and are designated as available-for-sale. These investments are included within “Other investments” on the Consolidated Balance Sheets. Unrealized gains and losses, net of deferred income taxes, are recorded to accumulated other comprehensive income or loss. These investments are monitored for other than temporary declines in market value. Realized gains and losses and permanent impairments are reflected in the Statements of Consolidated Income (Loss). No material impairment charges were recorded for the years ended December 31, 2020, 2019 or 2018. Refer to Note 18, "Fair Value," for additional information. F. Basis of Accounting for Rate-Regulated Subsidiaries. Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are later recognized in income as the related amounts are included in customer rates and recovered from or refunded to customers. We continually evaluate whether or not our operations are within the scope of ASC 980 and rate regulations. As part of that analysis, we evaluate probability of recovery for our regulatory assets. In management’s opinion, our regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Refer to Note 9, "Regulatory Matters," for additional information. G. Plant and Other Property and Related Depreciation and Maintenance. Property, plant and equipment (principally utility plant) is stated at cost. Our rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the electric, gas and common properties, as approved by the appropriate regulators. Non-utility property includes renewable generation assets owned by a joint venture of which we are the primary beneficiary and is generally depreciated on a straight-line basis over the life of the associated asset. Refer to Note 6, "Property, Plant and Equipment," for additional information related to depreciation expense. For rate-regulated companies, AFUDC is capitalized on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. Our pre-tax rate for AFUDC was 2.6% in 2020, 3.0% in 2019 and 3.5% in 2018. Generally, our subsidiaries follow the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When our subsidiaries retire regulated property, plant and equipment, original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable a regulated asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the gross amounts are classified as "Non-Utility and Other " as described in Note 6, "Property, Plant and Equipment." If the asset is no longer operating but still subject to recovery, the net amount is classified in "Regulatory assets" on the Consolidated Balance Sheets. If we are able to recover a full return of and on investment, the carrying value of the asset is based on historical cost. If we are not able to recover a full return on investment, a loss on impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When our subsidiaries sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from "Net Property, Plant and Equipment" on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. Refer to Note 6, "Property, Plant and Equipment," for further information. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years External and internal up-front implementation costs associated with cloud computing arrangements that are service contracts are deferred on the Consolidated Balance Sheets. Once the installed software is ready for its intended use, such deferred costs are amortized on a straight-line basis to "Operation and maintenance," over the minimum term of the contract plus contractually-provided renewal periods that are reasonable expected to be exercised. H. Goodwill and Other Intangible Assets. Substantially all of our goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. We test our goodwill for impairment annually as of May 1, or more frequently if events and circumstances indicate that goodwill might be impaired. Fair value of our reporting units is determined using a combination of income and market approaches. See Note 7, "Goodwill and Other Intangible Assets," for additional information. I. Accounts Receivable Transfer Program. Certain of our subsidiaries have agreements with third parties to transfer certain accounts receivable without recourse. These transfers of accounts receivable are accounted for as secured borrowings. The entire gross receivables balance remains on the December 31, 2020 and 2019 Consolidated Balance Sheets and short-term debt is recorded in the amount of proceeds received from the transferees involved in the transactions. Refer to Note 19, "Transfers of Financial Assets," for further information. J. Gas Cost and Fuel Adjustment Clause. Our regulated subsidiaries defer most differences between gas and fuel purchase costs and the recovery of such costs in revenues and adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. These deferred balances are recorded as "Regulatory assets" or "Regulatory liabilities," as appropriate, on the Consolidated Balance Sheets. Refer to Note 9, "Regulatory Matters," for additional information. K. Inventory. Both the LIFO inventory methodology and the weighted average cost methodology are used to value natural gas in storage, as approved by regulators for all of our regulated subsidiaries. Inventory valued using LIFO was $42.3 million and $47.2 million at December 31, 2020 and 2019, respectively. Based on the average cost of gas using the LIFO method, the estimated replacement cost of gas in storage was less than the stated LIFO cost by $19.6 million and $25.5 million at December 31, 2020 and 2019, respectively. Gas inventory valued using the weighted average cost methodology was $148.8 million at December 31, 2020 and $203.7 million at December 31, 2019. Electric production fuel is valued using the weighted average cost inventory methodology, as approved by NIPSCO's regulator. Materials and supplies are valued using the weighted average cost inventory methodology. L. Accounting for Exchange and Balancing Arrangements of Natural Gas. Our Gas Distribution Operations segment enters into balancing and exchange arrangements of natural gas as part of its operations and off-system sales programs. We record a receivable or payable for any of our respective cumulative gas imbalances, as well as for any gas inventory borrowed or lent under a Gas Distribution Operations exchange agreement. Exchange gas is valued based on individual regulatory jurisdiction requirements (for example, historical spot rate, spot at the beginning of the month). These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on our Consolidated Balance Sheets, as appropriate. M. Accounting for Risk Management Activities. We account for our derivatives and hedging activities in accordance with ASC 815. We recognize all derivatives as either assets or liabilities on the Consolidated Balance Sheets at fair value, unless such contracts are exempted as a normal purchase normal sale under the provisions of the standard. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation. We have elected not to net fair value amounts for any of our derivative instruments or the fair value amounts recognized for the right to receive cash collateral or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. See Note 10, "Risk Management Activities," for additional information. N. Income Taxes and Investment Tax Credits. We record income taxes to recognize full interperiod tax allocations. Under the asset and liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amount and the tax basis of existing assets and liabilities. Investment tax credits associated with regulated operations are deferred and amortized as a reduction to income tax expense over the estimated useful lives of the related properties. To the extent certain deferred income taxes of the regulated companies are recoverable or payable through future rates, regulatory assets and liabilities have been established. Regulatory assets for income taxes are primarily attributable to property-related tax timing differences for which deferred taxes had not been provided in the past, when regulators did not recognize such taxes as costs in the rate-making process. Regulatory liabilities for income taxes are primarily attributable to the regulated companies’ obligation to refund to ratepayers deferred income taxes provided at rates higher than the current Federal income tax rate. Such property-related amounts are credited to ratepayers using either the average rate assumption method or the reverse South Georgia method. Non property-related amounts are credited to ratepayers consistent with state utility commission direction. Pursuant to the Internal Revenue Code and relevant state taxing authorities, we and our subsidiaries file consolidated income tax returns for federal and certain state jurisdictions. We and our subsidiaries are parties to a tax sharing agreement. Income taxes recorded by each party represent amounts that would be owed had the party been separately subject to tax. O. Environmental Expenditures. We accrue for costs associated with environmental remediation obligations, including expenditures related to asset retirement obligations and cost of removal, when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The accruals for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Other accruals” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. Rate-regulated subsidiaries applying regulatory accounting establish regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Refer to Note 8, "Asset Retirement Obligations," and Note 20, "Other Commitments and Contingencies," for further information. P. Excise Taxes. As an agent for some state and local governments, we invoice and collect certain excise taxes levied by state and local governments on customers and record these amounts as liabilities payable to the applicable taxing jurisdiction. Such balances are presented within "Other accruals" on the Consolidated Balance Sheets. These types of taxes collected from customers, comprised largely of sales taxes, are presented on a net basis affecting neither revenues nor cost of sales. We account for excise taxes for which we are liable by recording a liability for the expected tax with a corresponding charge to “Other taxes” expense on the Statements of Consolidated Income (Loss).

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
Recent Accounting Pronouncements	Dec. 31, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Pronouncements We are currently evaluating the impact of certain ASUs on our Consolidated Financial Statements or Notes to Consolidated Financial Statements, which are described below: Standard Description Effective Date Effect on the financial statements or other significant matters ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Statement This pronouncement provides Upon issuance on We continue to evaluate the temporary expedients and options available under this guidance, and the effects of these pronouncements on our Consolidated Financial Statements and Notes to Consolidated Financial Statements. We are currently identifying and evaluating contracts that may be impacted. As of December 31, 2020, we have not applied any expedients and options available under this ASU. ASU 2021-01, Reference Rate Reform (Topic 848): Scope Standard Description Effective Date Effect on the financial statements or other significant matters ASU 2020-06, Debt with Conversion and Other Options (Subtopic 470-20) and Derivative and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity's Own Equity This pronouncement simplifies Annual period This pronouncement does not impact any securities we currently have on our balance sheet. We will continue to Recently Adopted Accounting Pronouncements Standard Adoption ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (ASC 326). ASC 326 revised the GAAP guidance on the impairment of most financial assets and certain other instruments that are not measured at fair value through net income. ASC 326 introduces the current expected credit loss (CECL) model that is based on expected losses for ASU 2016-13, Financial Instruments-Credit Losses (Topic 326) ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans Issued in August 2018, the pronouncement modifies the disclosure requirements for defined benefit pension or other postretirement benefit plans. The guidance removes disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and adds disclosure requirements identified as relevant. The modifications affect annual period disclosures for fiscal years ending after December 15, 2020, and are applied on a retrospective basis to all periods presented. These disclosure requirements are reflected in the Note 12, "Pension and Postretirement Benefits." ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes This pronouncement simplifies the accounting for income taxes by eliminating certain exceptions to the general principles in ASC 740, income taxes. It also improves consistency of application for other areas of the guidance by clarifying and amending existing guidance. We adopted the amendments of this pronouncement as of January 1, 2021 with no material impact to the Consolidated Financial Statements.

Revenue Recognition

Revenue Recognition	12 Months Ended
Revenue Recognition	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	Revenue Recognition Customer Revenues. Substantially all of our revenues are tariff-based. Under ASC 606, the recipients of our utility service meet the definition of a customer, while the operating company tariffs represent an agreement that meets the definition of a contract, which creates enforceable rights and obligations. Customers in certain of our jurisdictions participate in programs that allow for a fixed payment each month regardless of usage. Payments received that exceed the value of gas or electricity actually delivered are recorded as a liability and presented in "Customer Deposits and Credits" on the Consolidated Balance Sheets. Amounts in this account are reduced and revenue is recorded when customer usage exceeds payments received. We have identified our performance obligations created under tariff-based sales as 1) the commodity (natural gas or electricity, which includes generation and capacity) and 2) delivery. These commodities are sold and / or delivered to and generally consumed by customers simultaneously, leading to satisfaction of our performance obligations over time as gas or electricity is delivered to customers. Due to the at-will nature of utility customers, performance obligations are limited to the services requested and received to date. Once complete, we generally maintain no additional performance obligations. Transaction prices for each performance obligation are generally prescribed by each operating company’s respective tariff. Rates include provisions to adjust billings for fluctuations in fuel and purchased power costs and cost of natural gas. Revenues are adjusted for differences between actual costs, subject to reconciliation, and the amounts billed in current rates. Under or over recovered revenues related to these cost recovery mechanisms are included in "Regulatory Assets" or "Regulatory Liabilities" on the Consolidated Balance Sheets and are recovered from or returned to customers through adjustments to tariff rates. As we provide and deliver service to customers, revenue is recognized based on the transaction price allocated to each performance obligation. Distribution revenues are generally considered daily or "at-will" contracts as customers may cancel their service at any time (subject to notification requirements), and revenue generally represents the amount we are entitled to bill customers. In addition to tariff-based sales, our Gas Distribution Operations segment enters into balancing and exchange arrangements of natural gas as part of our operations and off-system sales programs. We have concluded that these sales are within the scope of ASC 606. Performance obligations for these types of sales include transportation and storage of natural gas and can be satisfied at a point in time or over a period of time, depending on the specific transaction. For those transactions that span a period of time, we record a receivable or payable for any cumulative gas imbalances, as well as for any gas inventory borrowed or lent under a Gas Distributions Operations exchange agreement. Revenue Disaggregation and Reconciliation. We disaggregate revenue from contracts with customers based upon reportable segment as well as by customer class. As our revenues are primarily earned over a period of time, and we do not earn a material amount of revenues at a point in time, revenues are not disaggregated as such below. The Gas Distribution Operations segment provides natural gas service and transportation for residential, commercial and industrial customers in Ohio, Pennsylvania, Virginia, Kentucky, Maryland, Indiana and Massachusetts. We completed the sale of the Massachusetts Business on October 9, 2020. The Electric Operations segment provides electric service in 20 counties in the northern part of Indiana. The table below reconciles revenue disaggregation by customer class to segment revenue as well as to revenues reflected on the Statements of Consolidated Income (Loss): Year Ended December 31, 2020 (in millions) Gas Distribution Operations Electric Operations Corporate and Other (2) Total Customer Revenues (1) Residential $ 2,075.0 $ 527.8 $ — $ 2,602.8 Commercial 670.5 480.3 — 1,150.8 Industrial 212.8 412.1 — 624.9 Off-system 41.0 — — 41.0 Miscellaneous 32.7 20.2 0.8 53.7 Total Customer Revenues $ 3,032.0 $ 1,440.4 $ 0.8 $ 4,473.2 Other Revenues 96.1 95.5 16.9 208.5 Total Operating Revenues $ 3,128.1 $ 1,535.9 $ 17.7 $ 4,681.7 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues. (2) Other revenues related to the Transition Services Agreement entered into in connection with the sale of the Massachusetts Business. Year Ended December 31, 2019 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Customer Revenues (1) Residential $ 2,309.0 $ 481.6 $ — $ 2,790.6 Commercial 771.3 486.6 — 1,257.9 Industrial 245.2 607.7 — 852.9 Off-system 77.7 — — 77.7 Miscellaneous 52.0 21.5 0.8 74.3 Total Customer Revenues $ 3,455.2 $ 1,597.4 $ 0.8 $ 5,053.4 Other Revenues 54.5 101.0 — 155.5 Total Operating Revenues $ 3,509.7 $ 1,698.4 $ 0.8 $ 5,208.9 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues. Year Ended December 31, 2018 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Customer Revenues (1) Residential $ 2,250.0 $ 494.7 $ — $ 2,744.7 Commercial 751.9 492.7 — 1,244.6 Industrial 228.0 613.6 — 841.6 Off-system 92.4 — — 92.4 Miscellaneous 49.7 17.4 0.7 67.8 Total Customer Revenues $ 3,372.0 $ 1,618.4 $ 0.7 $ 4,991.1 Other Revenues 34.4 89.0 — 123.4 Total Operating Revenues $ 3,406.4 $ 1,707.4 $ 0.7 $ 5,114.5 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues. Other Revenues. As permitted by accounting principles generally accepted in the United States, regulated utilities have the ability to earn certain types of revenue that are outside the scope of ASC 606. These revenues primarily represent revenue earned under alternative revenue programs. Alternative revenue programs represent regulator-approved mechanisms that allow for the adjustment of billings and revenue for certain approved programs. We maintain a variety of these programs, including demand side management initiatives that recover costs associated with the implementation of energy efficiency programs, as well as normalization programs that adjust revenues for the effects of weather or other external factors. Additionally, we maintain certain programs with future test periods that operate similarly to FERC formula rate programs and allow for recovery of costs incurred to replace aging infrastructure. When the criteria to recognize alternative revenue have been met, we establish a regulatory asset and present revenue from alternative revenue programs on the Statements of Consolidated Income (Loss) as “Other revenues.” When amounts previously recognized under alternative revenue accounting guidance are billed, we reduce the regulatory asset and record a customer account receivable. Customer Accounts Receivable. Accounts receivable on our Consolidated Balance Sheets includes both billed and unbilled amounts, as well as certain amounts that are not related to customer revenues. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the date of the last cycle billing through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates and weather. The opening and closing balances of customer receivables for the years ended December 31, 2020 and 2019 are presented in the table below. We had no significant contract assets or liabilities during the period. Additionally, we have not incurred any significant costs to obtain or fulfill contracts. (in millions) Customer Accounts Receivable, Billed (less reserve) (1) Customer Accounts Receivable, Unbilled (less reserve) Balance as of December 31, 2019 $ 466.6 $ 346.6 Balance as of December 31, 2020 400.0 327.2 Decrease $ (66.6) $ (19.4) (1) Customer billed receivables decreased due to decreased natural gas costs and warmer weather in 2020 compared to 2019. Utility revenues are billed to customers monthly on a cycle basis. We generally expect that substantially all customer accounts receivable will be collected within the month following customer billing, as this revenue consists primarily of monthly, tariff-based billings for service and usage. We maintain common utility credit risk mitigation practices, including requiring deposits and actively pursuing collection of past due amounts. Our regulated operations also utilize certain regulatory mechanisms that facilitate recovery of bad debt costs within tariff-based rates, which provides further evidence of collectibility. In connection with the COVID-19 pandemic, certain state regulatory commissions instituted regulatory moratoriums that impacted our ability to pursue our standard credit risk mitigation practices. Following the issuance of these moratoriums, certain of our regulated operations have been authorized to recognize a regulatory asset for bad debt costs above levels currently in rates. We have reinstated our common credit mitigation practices where moratoriums have expired (see Note 9, "Regulatory Matters," for additional information on regulatory moratoriums and regulatory assets). It is probable that substantially all of the consideration to which we are entitled from customers will be collected upon satisfaction of performance obligations. Allowance for Credit Losses. We adopted ASC 326 effective January 1, 2020. See "Recently Adopted Accounting Pronouncements" in Note 2, "Recent Accounting Pronouncements," for more information about ASC 326. Each of our business segments pool their customer accounts receivables based on similar risk characteristics, such as customer type, geography, payment terms, and related macro-economic risks. Expected credit loss exposure is evaluated separately for each of our accounts receivable pools. Expected credit losses are established using a model that considers historical collections experience, current information, and reasonable and supportable forecasts. Relevant and reliable internal and external inputs used in the model include, but are not limited to, energy consumption trends, revenue projections, actual charge-offs data, recoveries data, shut-off orders executed data, and final bill data. We continuously evaluate available reasonable and supportable information relevant to assessing collectibility of current and future receivables. We evaluate creditworthiness of specific customers periodically or when required by changes in facts and circumstances. When we become aware of a specific commercial or industrial customer's inability to pay, an allowance for expected credit losses is recorded for the relevant amount. We also monitor other circumstances that could affect our overall expected credit losses; these include, but are not limited to, creditworthiness of overall population in service territories, adverse conditions impacting an industry sector, and current economic conditions. At each reporting period, we record expected credit losses using an allowance for credit losses account. When deemed to be uncollectible, customer accounts are written-off. A rollforward of our allowance for credit losses for the year ended December 31, 2020 are presented in the table below: Year Ended December 31, 2020 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Beginning balance (1) 9.1 3.1 0.8 13.0 Current period provisions 45.3 9.3 — 54.6 Write-offs charged against allowance (26.7) (3.0) — (29.7) Recoveries of amounts previously written off 14.1 0.3 — 14.4 Ending balance of the allowance for credit losses 41.8 9.7 0.8 52.3 (1) Total beginning balance differs from that presented in the Consolidated Balance Sheets as it excludes Columbia of Massachusetts. Columbia of Massachusetts' customer receivables and related allowance for credit losses were included in the sale of the Massachusetts Business that occurred on October 9, 2020.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
Variable Interest Entities	Dec. 31, 2020
Variable Interest Entities [Abstract]
Variable Interest Entities	Variable Interest Entities A VIE is an entity in which the controlling interest is determined through means other than a majority voting interest. The primary beneficiary of a VIE is the business enterprise which has the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance. Also, the primary beneficiary either absorbs a significant amount of the VIE’s losses or has the right to receive benefits that could be significant to the VIE. We consider these qualitative elements in determining whether we are the primary beneficiary of a VIE, and we consolidate those VIEs for which we are determined to be the primary beneficiary. Rosewater (a joint venture) owns and operates 102 MW of nameplate capacity wind generation assets. Members of the joint venture are NIPSCO (who is the managing member) and a tax equity partner. Earnings, tax attributes and cash flows are allocated to both NIPSCO and the tax equity partner in varying percentages by category and over the life of the partnership. Once the tax equity partner has earned their negotiated rate of return and we have reached the agreed upon contractual date, NIPSCO has the option to purchase at fair market value from the tax equity partner the remaining interest in the aforementioned joint venture. NIPSCO has an obligation to purchase, through a PPA at established market rates, 100% of the electricity generated by Rosewater. As the managing member of Rosewater, we control decisions that are significant to its ongoing operations and economic results. Therefore, we have concluded that we are the primary beneficiary of Rosewater and have consolidated Rosewater even though we own less than 100% of the total equity membership interest. We have determined that the use of HLBV accounting is reasonable and appropriate in order to attribute income and loss to the noncontrolling interest held by the tax equity partner. HLBV accounting was selected as the allocation of Rosewater's economic results to members differ from the members' relative ownership percentages. Using the HLBV method, our earnings are calculated based on how the partnership would distribute its cash if it were to hypothetically sell all of its assets for their carrying amounts and liquidate at each reporting period. Under HLBV, we calculate the liquidation value allocable to each partner at the beginning and end of each period based on the contractual terms of the related entity's operating agreement and adjust our income for the period to reflect the change our associated book value. In December 2020, in exchange for their respective membership interests in Rosewater, NIPSCO contributed $0.7 million in cash, and the tax equity partner contributed $86.1 million in cash, the first of two contractual cash contributions for each partner, per the equity capital contribution agreement. NIPSCO's remaining economic interest was acquired by assuming an obligation of $69.7 million to the developer, which comes due in 2023 and is included in "Other noncurrent liabilities" in the Consolidated Balance Sheets. From the contributed funds, Rosewater paid $85.3 million to the developer of the wind generation assets. The developer of the facility is not a partner in the joint venture for federal income tax purposes and does not receive any share of earnings, tax attributes, or cash flows of Rosewater. Once asset construction is complete, NIPSCO and the tax equity partner will each make a second cash contribution of $0.1 million and $7.5 million, respectively, and NIPSCO will assume an additional obligation to the developer of $6.0 million, totaling contributions of $170.1 million for both partners. We did not provide any financial or other support during the year that was not previously contractually required, nor do we expect to provide such support in the future. At December 31, 2020, $156.4 million in net assets (as detailed in the table below) related to Rosewater and the non-controlling interest attributable to the unrelated tax equity partner of $85.6 million were included in the Consolidated Balance Sheets. For the year ended December 31, 2020 $3.4 million was allocated to the tax equity partner and is included in "Net income attributable to non-controlling interest" on the Statements of Consolidated Income (Loss). At December 31, 2020, our consolidated balance sheet included the following assets and liabilities associated with Rosewater: (in millions) Net Property, Plant and Equipment $ 175.6 Current assets 1.7 Total assets (1) $ 177.3 Current liabilities $ 15.3 Asset retirement obligations 5.5 Other noncurrent liabilities 0.1 Total liabilities $ 20.9 (1) The assets of Rosewater represent assets of a consolidated VIE that can be used only to settle obligations of the consolidated VIE.

Earnings Per Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic EPS is computed by dividing net income attributable to common shareholders by the weighted-average number of shares of common stock outstanding for the period. The weighted-average shares outstanding for diluted EPS includes the incremental effects of the various long-term incentive compensation plans and forward agreements when the impact of such plans and agreements would be dilutive. The calculation of diluted earnings per share for the years ended December 31, 2020 and December 31, 2018 does not include any dilutive potential common shares as we had a net loss on the Statements of Consolidated Income (Loss) for these periods, and any incremental shares would have had an anti-dilutive impact on EPS. The computation of diluted average common shares is as follows: Year Ended December 31, (in thousands) 2020 2019 2018 Denominator Basic average common shares outstanding 384,347 374,650 356,491 Dilutive potential common shares: Shares contingently issuable under employee stock plans — 929 — Shares restricted under employee stock plans — 154 — Forward agreements — 253 — Diluted Average Common Shares 384,347 375,986 356,491

Property, Plant And Equipment

Property, Plant And Equipment	12 Months Ended
Property, Plant And Equipment	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant And Equipment	Property, Plant and Equipment Our property, plant and equipment on the Consolidated Balance Sheets are classified as follows: At December 31, (in millions) 2020 2019 Property, Plant and Equipment Gas Distribution Utility (1) $ 14,010.2 $ 14,989.7 Electric Utility (1) 6,478.0 8,902.3 Corporate 197.3 153.3 Construction Work in Process 572.6 457.3 Renewable Generation Assets (2) 175.7 — Non-Utility and Other (3) 2,746.1 39.3 Total Property, Plant and Equipment $ 24,179.9 $ 24,541.9 Accumulated Depreciation and Amortization Gas Distribution Utility (1) $ (3,292.9) $ (3,556.0) Electric Utility (1) (2,305.0) (3,973.8) Corporate (109.3) (79.5) Renewable Generation Assets (2) (0.1) — Non-Utility and Other (3) (1,853.1) (20.4) Total Accumulated Depreciation and Amortization $ (7,560.4) $ (7,629.7) Net Property, Plant and Equipment $ 16,619.5 $ 16,912.2 (1) NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment. (2) Our renewable generation assets are part of our electric segment and represent Non-Utility Property, owned and operated by Rosewater Wind Generation LLC, a joint venture between NIPSCO and unrelated tax equity partner, and depreciated straight-line over 30 years. Refer to Note 4, "Variable Interest Entities" for additional information. (3) Non-Utility and Other as of December 31, 2020 includes net book value of $903.8 million related to R.M. Schahfer Generating Station, which was reclassified from Electric Utility in the second quarter of 2020. Depreciation expense for the remaining net book value continues to be recorded at the composite depreciation rate approved by the IURC. See Note 20-E, "Other Matters," for additional information. The weighted average depreciation provisions for utility plant, as a percentage of the original cost, for the periods ended December 31, 2020, 2019 and 2018 were as follows: 2020 2019 2018 Electric Operations (1) 3.4 % 2.8 % 2.9 % Gas Distribution Operations 2.3 % 2.5 % 2.2 % (1) Increased rate beginning in 2020 primarily attributable to higher depreciation rates from the recent rate case proceeding. We recognized depreciation expense of $655.6 million, $612.2 million and $503.4 million for the years ended 2020, 2019 and 2018, respectively. Amortization of Software Costs. We amortized $56.7 million, $55.5 million and $54.1 million in 2020, 2019 and 2018, respectively, related to software costs. Our unamortized software balance was $136.4 million and $169.6 million at December 31, 2020 and 2019, respectively.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
Goodwill and Other Intangible Assets	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill And Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill. Substantially all of our goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. The following presents our goodwill balance allocated by segment as of December 31, 2020 and 2019: (in millions) 2020 2019 Gas Distribution Operations $ 1,485.9 $ 1,485.9 Electric Operations — — Corporate and Other — — Total $ 1,485.9 $ 1,485.9 For our annual goodwill impairment analysis performed as of May 1, 2020, we completed a quantitative ("step 1") fair value measurement of our reporting units. Fair value of this reporting unit was determined based on a weighting of income and market approaches. The income approach calculated discounted cash flows using updated cash flow projections, discount rates and return on equity assumptions. The market approach applied a combination of comparable company multiples and comparable transactions and used the most recent cash flow projections. The test indicated that the fair value of each of the reporting units that are allocated goodwill exceeded their carrying values, indicating that no impairment was necessary. Columbia of Massachusetts was not considered to be a reporting unit for May 1, 2020 fair value measurement as the goodwill balance had been reduced to zero as of December 31, 2019. During the fourth quarter of 2019, in connection with the preparation of the year-end financial statements, we assessed the matters related to the then proposed sale of the Massachusetts Business and determined a new impairment analysis was required for our Columbia of Massachusetts reporting unit. The fair value of the Columbia of Massachusetts reporting unit was determined in the same manner as described above for our remaining reporting units. The 2019 year-end impairment analysis indicated that the fair value of the Columbia of Massachusetts reporting unit was below its carrying value. As a result, we reduced the Columbia of Massachusetts reporting unit goodwill balance to zero and recognized a goodwill impairment charge totaling $204.8 million, which is non-deductible for tax purposes. Intangible and Other Long-Lived Assets Impairment. We review our definite-lived intangible assets, along with other long-lived assets (utility plant), for impairment when events or changes in circumstances indicate the assets' fair value might be below their carrying amount. Prior to December 31, 2019, our intangible assets, apart from goodwill, consisted of franchise rights. Franchise rights were identified as part of the purchase price allocations associated with the acquisition in February 1999 of Columbia of Massachusetts. During the fourth quarter of 2019, in connection with the preparation of the year-end financial statements, we assessed the changes in circumstances that occurred during the quarter to determine if it was more likely than not that the fair value of our long-lived assets (including franchise rights) were below their carrying amount. As a result, we performed a year-end impairment test of our held and used long-lived assets in which we compared the book value of the Columbia of Massachusetts asset group to its undiscounted future cash flow and determined the carrying value of the asset group was not recoverable. We estimated the fair value of the Columbia of Massachusetts asset group using a weighting of income and market approaches and determined that the fair value was less than the carrying value. The resulting impairment was allocated to reduce the entire franchise rights book value to its fair value of zero, which resulted in an impairment charge totaling $209.7 million recorded in the Gas Distribution Operations segment during the year ended December 31, 2019. As of December 31, 2020 and 2019, the carrying amount of the franchise rights was zero. We recorded zero amortization expense in 2020 and $11.0 million in 2019 and 2018 related to our franchise rights intangible asset.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
Asset Retirement Obligations	Dec. 31, 2020
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement ObligationsWe have recognized asset retirement obligations associated with various legal obligations including costs to remove and dispose of certain construction materials located within many of our facilities, certain costs to retire pipeline, removal costs for certain underground storage tanks, removal of certain pipelines known to contain PCB contamination, closure costs for certain sites including ash ponds, solid waste management units and a landfill, as well as some other nominal asset retirement obligations. We also have an obligation associated with the decommissioning of our two hydro facilities located in Indiana. These hydro facilities have an indeterminate life, and as such, no asset retirement obligation has been recorded. Changes in our liability for asset retirement obligations for the years 2020 and 2019 are presented in the table below: (in millions) 2020 2019 Beginning Balance $ 416.9 $ 352.0 Accretion recorded as a regulatory asset/liability 17.3 15.7 Additions 5.5 — Settlements (13.9) (5.4) Change in estimated cash flows 86.0 (1) 54.6 (2) Other (16.2) (3) — Ending Balance $ 495.6 $ 416.9 (1) The change in estimated cash flows for 2020 is primarily attributed to revisions to the estimated costs associated with refining the CCR compliance plan, changes in estimated costs for electric generating stations and the changes in estimated costs for retirement of gas mains. See Note 20-D. "Environmental Matters" for additional information on CCRs. (2) The change in estimated cash flows for 2019 is primarily attributed to changes in estimated costs and settlement timing for electric generating stations and the changes in estimated costs for retirement of gas mains. (3) Represents the Columbia of Massachusetts Asset Retirement Obligations that were included in the sale of the Massachusetts Business that occurred on October 9, 2020. Certain non-legal costs of removal that have been, and continue to be, included in depreciation rates and collected in the customer rates of the rate-regulated subsidiaries are classified as "Regulatory liabilities" on the Consolidated Balance Sheets.

Regulatory Matters

Regulatory Matters	12 Months Ended
Regulatory Matters	Dec. 31, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters Regulatory Assets and Liabilities We follow the accounting and reporting requirements of ASC Topic 980, which provides that regulated entities account for and report assets and liabilities consistent with the economic effect of regulatory rate-making procedures when the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates will be charged and collected from customers. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income or expense are deferred on the balance sheet and are recognized in the income statement as the related amounts are included in customer rates and recovered from or refunded to customers. We assess the probability of collection for all of our regulatory assets each period. Regulatory assets were comprised of the following items: At December 31, (in millions) 2020 2019 Regulatory Assets Unrecognized pension and other postretirement benefit costs (see Note 12) $ 583.3 $ 739.1 Deferred pension and other postretirement benefit costs (see Note 12) 72.4 91.3 Environmental costs (see Note 20-D) 56.6 73.4 Regulatory effects of accounting for income taxes (see Note 1-N and Note 11) 194.5 234.0 Under-recovered gas and fuel costs (see Note 1-J) 8.0 3.9 Depreciation 192.6 210.7 Post-in-service carrying charges 228.6 219.8 Safety activity costs 146.0 118.6 DSM programs 37.8 50.1 Bailly Generating Station 204.7 221.8 Losses on Commodity Price Risk Programs (See Note 10) 54.7 76.4 Deferred Property Taxes 62.9 60.3 Other 88.4 140.2 Total Regulatory Assets $ 1,930.5 $ 2,239.6 Less: Current Portion 135.7 225.7 Total Noncurrent Regulatory Assets $ 1,794.8 $ 2,013.9 Regulatory liabilities were comprised of the following items: At December 31, (in millions) 2020 2019 Regulatory Liabilities Over-recovered gas and fuel costs (see Note 1-J) $ 47.8 $ 42.6 Cost of removal (see Note 8) 775.2 1,047.5 Regulatory effects of accounting for income taxes (see Note 1-N and Note 11) 1,105.1 1,307.0 Deferred pension and other postretirement benefit costs (see Note 12) 69.5 64.7 Other 67.9 50.4 Total Regulatory Liabilities $ 2,065.5 $ 2,512.2 Less: Current Portion 161.3 160.2 Total Noncurrent Regulatory Liabilities $ 1,904.2 $ 2,352.0 Regulatory assets, including under-recovered gas and fuel costs and depreciation, of approximately $1,260.6 million and $1,524.3 million as of December 31, 2020 and 2019, respectively, are not earning a return on investment. These costs are recovered over a remaining life, the longest of which is 41 years. Assets: Unrecognized pension and other postretirement benefit costs. Represents the deferred other comprehensive income or loss of the actuarial gains or losses and the prior service costs or credits that arise during the period but that are not immediately recognized as components of net periodic benefit costs by certain subsidiaries that will ultimately be recovered through base rates. Deferred pension and other postretirement benefit costs. Primarily relates to the difference between defined benefit plan expense recorded by certain subsidiaries due to regulatory orders and the corresponding expense that would otherwise be recorded in accordance with GAAP. The majority of these amounts are driven by Columbia of Ohio. The timeframe for the recovery of these costs will be addressed in the next base rate case, and the costs are expected to be collected through future base rates, revenue riders or tracking mechanisms. Environmental costs. Includes certain recoverable costs related to gas plant sites, disposal sites or other sites onto which material may have migrated, the recovery of which is to be addressed in future base rates, billing riders or tracking mechanisms of certain of our subsidiaries. Regulatory effects of accounting for income taxes. Represents the deferral and under collection of deferred taxes in the rate making process. Under-recovered gas and fuel costs. Represents the difference between the costs of gas and fuel and the recovery of such costs in revenue and is used to adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. Recovery of these costs is achieved through tracking mechanisms. Depreciation. Represents differences between depreciation expense incurred on a GAAP basis and that prescribed through regulatory order. The majority of this balance is driven by Columbia of Ohio's IRP and CEP deferrals. Recovery of these amounts is approved annually through the related riders. Post-in-service carrying charges. Represents deferred debt-based carrying charges incurred on certain assets placed into service but not yet included in customer rates. The majority of this balance is driven by Columbia of Ohio's IRP and CEP deferrals. Safety activity costs. Represents the difference between costs incurred by certain of our subsidiaries in eligible safety programs in compliance with PHMSA regulations in excess of those being recovered in rates. DSM programs. Represents costs associated with Gas Distribution Operations and Electric Operations segments' energy efficiency and conservation programs. Costs are recovered through tracking mechanisms. Bailly Generating Station. Represents the net book value of Units 7 and 8 of Bailly Generating Station that was retired during 2018. These amounts are currently being amortized at a rate consistent with their inclusion in customer rates. Losses on Commodity Price Risk Programs . Represents the unrealized losses related to certain of our subsidiary's commodity price risk programs. These programs help to protect against the volatility of commodity prices and these amounts are collected from customers through their inclusion in customer rates. Property Taxes . Represents the deferral and under collection of property taxes in the rate making process for Columbia of Ohio and is driven by the IRP and CEP deferrals. Liabilities: Over-recovered gas and fuel costs. Represents the difference between the cost of gas and fuel and the recovery of such costs in revenues and is the basis to adjust future billings for such refunds on a basis consistent with applicable state-approved tariff provisions. Refunding of these revenues is achieved through tracking mechanisms. Cost of removal. Represents anticipated costs of removal for utility assets that have been collected through depreciation rates for future costs to be incurred. Regulatory effects of accounting for income taxes. Represents amounts owed to customers for deferred taxes collected at a higher rate than the current statutory rates and liabilities associated with accelerated tax deductions owed to customers. Balance includes excess deferred taxes recorded upon implementation of the TCJA in December 2017, net of amounts amortized through 2020. Deferred pension and other postretirement benefit costs. Primarily represents cash contributions in excess of postretirement benefit expense that is deferred by certain subsidiaries. COVID-19 Regulatory Filings In response to the COVID-19 pandemic, we have engaged, or have received directives from, the regulatory commissions in the states in which we operate, as described below. Columbia of Ohio filed a Deferral Application and a Transition Plan with the PUCO on May 29, 2020. The Deferral Application requested approval to record a regulatory asset for pandemic incremental costs, foregone revenue from late payment fees, and bad debt expense from certain classes of customers. An order approving the Deferral Application was received on July 15, 2020. The Transition Plan requested the resumption of activities that were suspended in March 2020, including resumption of disconnects due to non-payment and billing of late payment fees beginning with the August 2020 billing cycle. The PUCO approved the Transition Plan on June 17, 2020. As of December 31, 2020, $2.0 million of incremental pandemic-related costs were deferred to a regulatory asset. NIPSCO received a COVID-19 pandemic order from the IURC on June 29, 2020. This order extended the disconnection moratorium and the suspension of collection of late payment fees, deposits and reconnection fees through August 14, 2020. The order requires utilities to offer payment arrangements of at least six months and requires NIPSCO to provide the IURC with information about NIPSCO’s communications with delinquent customers. On August 12, 2020, the IURC issued an order affirming the expiration of the disconnect moratorium after August 14, 2020, while requiring that six month payment plans be offered to all customers and extending the suspension for collection of late payment fees, deposits, and reconnection fees through October 12, 2020 for residential customers only. On October 7, 2020 the Office of Utility Consumer Counselor ("OUCC") filed a motion for the IURC to extend these temporary consumer protections for an additional 60 days. On October 27, the IURC issued a docket entry denying the OUCC's motion. The June 29, 2020 order also authorized NIPSCO to create a regulatory asset for pandemic-related incremental bad debt expense as well as the costs to implement the requirements of the order. As of December 31, 2020, $9.2 million of incremental bad debt expense and costs to implement the requirements of the order were deferred to a regulatory asset. Columbia of Pennsylvania received a secretarial letter issued by the Pennsylvania PUC on May 13, 2020 authorizing Pennsylvania utilities to create a regulatory asset for incremental bad debt expense incurred since March 13, 2020, above levels currently in rates. While Columbia of Pennsylvania is not authorized to defer any other incremental costs, it is required to track extraordinary non-recurring costs, and any offsetting benefits received, in connection with the COVID-19 pandemic. On October 13, 2020, the Pennsylvania PUC entered an order modifying its March 13, 2020 emergency order that had established a moratorium on utility service terminations. As modified, the moratorium still applies to residential customers with incomes at or below 300% of the federal poverty income guidelines (“protected customers”). For all other customers, the moratorium was lifted on November 9, 2020, but utilities must comply with several notice requirements beyond those already in place in Pennsylvania in order to proceed with service terminations. For residential customers who are subject to termination under the revised moratorium, as of December 1, 2020, the standard winter service moratorium will be in effect until April 1, 2021, which will render service termination for delinquent accounts impractical during that period. Additionally, the October 13, 2020 order authorizes utilities to create a regulatory asset for any incremental expenses incurred above those embedded in rates resulting from the directives contained in the Order. As of December 31, 2020, $5.4 million of incremental bad debt expense was deferred to a regulatory asset. On March 16, 2020, the VSCC ordered a moratorium on service disconnections for unpaid bills due to the effects of the COVID-19 pandemic. The order also suspended late payment fees, required utilities to offer payment plans of up to 12 months, and required utilities to provide certain information about customer accounts receivables to the VSCC. Columbia of Virginia received an order from the VSCC on April 29, 2020 authorizing Columbia of Virginia to create a regulatory asset for incremental bad debt expense, suspended late payment fees, reconnection costs, carrying costs and other incremental prudently incurred costs related to the pandemic. The VSCC moratorium expired on October 6, 2020; however, the directives requiring utilities to offer payment plans of up to 12 months and suspending service disconnections or charging of late payment fees to customers that are current on such payment plans remain in effect. On November 18, 2020, legislation was enacted that extended the moratorium on residential service disconnections and late payment fees until the Governor determines that the economic and public health conditions have improved such that the prohibition does not need to be in place, or until at least 60 days after such declared state of emergency ends, whichever is sooner. Recovery of any regulatory asset will be addressed in future base rate proceedings and is subject to an earnings test review. On August 31, 2020, the Maryland PSC issued an emergency order that extended the Governor's order prohibiting residential service terminations through October 1, 2020. The emergency order also requires Maryland utilities that proceed with residential service terminations after that date to provide at least 45 days notice prior to terminating service; to offer structured payment plans to applicable residential customers with a minimum of 12 months to repay, or 24 months for certified low income customers; the requirement or collection of down payments or deposits as a condition of beginning a payment plan by any residential customer; and cannot refuse to negotiate or deny a payment plan to a residential customer due to such customer's failure to meet the terms and conditions of an alternate payment plan during the past 18 months. Columbia of Maryland received an order issued by the Maryland PSC on April 9, 2020, authorizing Maryland utilities to create a regulatory asset for incremental COVID-19 pandemic-related costs, including incremental bad debt expense, incurred to ensure that customers have essential utility service during the state of emergency in Maryland. Such incremental costs must be offset by any benefit

Risk Management Activities

Risk Management Activities	12 Months Ended
Risk Management Activities	Dec. 31, 2020
Risk Management Activities [Abstract]
Risk Management Activities	Risk Management Activities We are exposed to certain risks related to our ongoing business operations; namely commodity price risk and interest rate risk. We recognize that the prudent and selective use of derivatives may help to lower our cost of debt capital, manage interest rate exposure and limit volatility in the price of natural gas. Risk management assets and liabilities on our derivatives are presented on the Consolidated Balance Sheets as shown below: December 31, (in millions) 2020 2019 Risk Management Assets - Current (1) Interest rate risk programs $ — $ — Commodity price risk programs 10.4 0.6 Total $ 10.4 $ 0.6 Risk Management Assets - Noncurrent (2) Interest rate risk programs $ — $ — Commodity price risk programs 2.8 3.8 Total $ 2.8 $ 3.8 Risk Management Liabilities - Current Interest rate risk programs $ 70.9 $ — Commodity price risk programs 7.3 12.6 Total $ 78.2 $ 12.6 Risk Management Liabilities - Noncurrent Interest rate risk programs $ 99.5 $ 76.2 Commodity price risk programs 45.1 57.8 Total $ 144.6 $ 134.0 (1) Presented in "Prepayments and other" on the Consolidated Balance Sheets. (2) Presented in "Deferred charges and other" on the Consolidated Balance Sheets. Commodity Price Risk Management We, along with our utility customers, are exposed to variability in cash flows associated with natural gas purchases and volatility in natural gas prices. We purchase natural gas for sale and delivery to our retail, commercial and industrial customers, and for most customers the variability in the market price of gas is passed through in their rates. Some of our utility subsidiaries offer programs whereby variability in the market price of gas is assumed by the respective utility. The objective of our commodity price risk programs is to mitigate the gas cost variability, for us or on behalf of our customers, associated with natural gas purchases or sales by economically hedging the various gas cost components using a combination of futures, options, forwards or other derivative contracts. NIPSCO received IURC approval to lock in a fixed price for its natural gas customers using long-term forward purchase instruments. The term of these instruments range from five Interest Rate Risk Management As of December 31, 2020, we have two forward-starting interest rate swaps with an aggregate notional value totaling $500.0 million to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the periods from the effective dates of the swaps to the anticipated dates of forecasted debt issuances, which are expected to take place by the end of 2024. These interest rate swaps are designated as cash flow hedges. The gains and losses related to these swaps are recorded to AOCI and will be recognized in "Interest expense, net" concurrently with the recognition of interest expense on the associated debt, once issued. If it becomes probable that a hedged forecasted transaction will no longer occur, the accumulated gains or losses on the derivative will be recognized currently in "Other, net" in the Statements of Consolidated Income (Loss). The passage of the TCJA and Greater Lawrence Incident led to significant changes to our long-term financing plan. As a result, during 2018, we settled forward-starting interest rate swaps with a notional value of $750.0 million. These derivative contracts were accounted for as cash flow hedges. As part of the transactions, the associated net unrealized gain of $46.2 million was recognized immediately in "Other, net" in the Statements of Consolidated Income (Loss) as it became probable the forecasted borrowing transactions would no longer occur. There were no amounts excluded from effectiveness testing for derivatives in cash flow hedging relationships at December 31, 2020, 2019 and 2018. Our derivative instruments measured at fair value as of December 31, 2020 and 2019 do not contain any credit-risk-related contingent features.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income Tax Expense. The components of income tax expense (benefit) were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Income Taxes Current Federal $ 0.2 $ — $ — State 11.7 5.2 8.2 Total Current 11.9 5.2 8.2 Deferred Federal (0.4) 110.7 (209.4) State (27.4) 9.0 22.2 Total Deferred (27.8) 119.7 (187.2) Deferred Investment Credits (1.2) (1.4) (1.0) Income Taxes $ (17.1) $ 123.5 $ (180.0) Statutory Rate Reconciliation. The following table represents a reconciliation of income tax expense at the statutory federal income tax rate to the actual income tax expense from continuing operations: Year Ended December 31, (in millions) 2020 2019 2018 Book income (loss) before income taxes $ (31.3) $ 506.6 $ (230.6) Tax expense (benefit) at statutory federal income tax rate (6.6) 21.0 % 106.5 21.0 % (48.4) 21.0 % Increases (reductions) in taxes resulting from: State income taxes, net of federal income tax benefit (11.7) 37.4 10.1 2.0 24.7 (10.7) Amortization of regulatory liabilities (38.4) 122.7 (29.4) (5.8) (29.3) 12.7 Goodwill impairment — — 43.0 8.5 — — Fines and penalties 11.8 (37.7) 11.5 2.3 0.2 (0.1) Charitable contribution carryover — — (2.5) (0.5) — — State regulatory proceedings — — (9.5) (1.9) (127.8) 55.4 Employee stock ownership plan dividends and other compensation (1.3) 4.2 (2.0) (0.4) (2.2) 1.0 Deferred taxes on TCJA regulatory liability divested 23.3 (74.5) — — — — Tax accrual adjustments 8.9 (28.4) — — — — Federal tax credits (2.5) 8.0 — — — — Other adjustments (0.6) 1.9 (4.2) (0.8) 2.8 (1.2) Income Taxes $ (17.1) 54.6 % $ 123.5 24.4 % $ (180.0) 78.1 % The effective income tax rates were 54.6%, 24.4% and 78.1% in 2020, 2019 and 2018, respectively. The difference in tax expense year-over-year has a relative impact on the effective tax rate proportional to pretax income or loss. The 30.2% increase in effective tax rate in 2020 versus 2019 was primarily the result of lower pre-tax income, state jurisdictional mix of pre-tax loss in 2020 tax effected at statutory tax rates and increased amortization of excess deferred federal income taxes in 2020 compared to 2019. These items were offset by increased deferred tax expense recognized on the sale of Columbia of Massachusetts' regulatory liability, established due to TCJA in 2017, that would have otherwise been recognized over the amortization period, non-deductible penalties as described in Note 1, "Company Structure and Principles of Consolidation" and non-cash impairment of goodwill related to Columbia of Massachusetts in 2019 (see Note 7, "Goodwill and Other Intangible Assets" for additional information), and one-time tax accrual adjustments. The 53.7% decrease in effective tax rate in 2019 versus 2018 was primarily the result of not having significant income tax decreases resulting from state regulatory proceedings as in 2018. Additionally, there was an increase in the effective tax rate related to the non-cash impairment of goodwill in 2019 related to Columbia of Massachusetts (see Note 7, "Goodwill and Other Intangible Assets" for additional information) and non-deductible fines and penalties related to the Greater Lawrence Incident (see Note 20, "Legal Proceedings" for additional information). The rate is also impacted by the relative impact of permanent differences on higher pre-tax income. Net Deferred Income Tax Liability Components. Deferred income taxes result from temporary differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. The principal components of our net deferred tax liability were as follows: At December 31, (in millions) 2020 2019 Deferred tax liabilities Accelerated depreciation and other property differences $ 2,339.3 $ 2,516.9 Other regulatory assets 331.8 381.5 Total Deferred Tax Liabilities 2,671.1 2,898.4 Deferred tax assets Other regulatory liabilities and deferred investment tax credits (including TCJA) 287.8 336.1 Pension and other postretirement/postemployment benefits 118.1 152.1 Net operating loss carryforward and AMT credit carryforward 602.1 765.9 Environmental liabilities 22.6 25.4 Other accrued liabilities 41.5 35.3 Other, net 128.4 98.3 Total Deferred Tax Assets 1,200.5 1,413.1 Net Deferred Tax Liabilities $ 1,470.6 $ 1,485.3 At December 31, 2020, we have federal net operating loss carryforwards of $520.8 million. The federal net operating loss carryforwards are available to offset taxable income and will begin to expire in 2037. In addition, we have $7.8 million in charitable contribution carryforwards to offset future taxable income, which begin to expire in 2023. We believe it is more likely than not that we will realize the benefit from the federal net operating loss carryforwards. We also have $81.4 million (net) of state net operating loss carryforwards. Depending on the jurisdiction in which the state net operating loss was generated, the carryforwards will begin to expire in 2028. We believe it is more likely than not that a portion of the benefit from certain state NOL carryforwards will not be realized. In recognition of this risk, we have provided a valuation allowance of $6.4 million (net) on the deferred tax assets related to sale of Massachusetts Business assets (see Note 1, "Company Structure and Principles of Consolidation" for additional information) reflected in the state net operating loss carryforward presented above. Unrecognized Tax Benefits. A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows: Reconciliation of Unrecognized Tax Benefits (in millions) 2020 2019 2018 Unrecognized Tax Benefits - Opening Balance $ 23.2 $ 1.2 $ 1.4 Gross decreases - tax positions in prior period (1.5) (0.6) (0.4) Gross increases - current period tax positions — 22.6 0.2 Unrecognized Tax Benefits - Ending Balance $ 21.7 $ 23.2 $ 1.2 Offset for net operating loss carryforwards (21.7) (22.6) — Balance - Less Net Operating Loss Carryforwards $ — $ 0.6 $ 1.2 In 2020, we resolved prior unrecognized tax benefits of $1.5 million. We present accrued interest on unrecognized tax benefits, accrued interest on other income tax liabilities and tax penalties in "Income Taxes" on our Statements of Consolidated Income (Loss). Interest expense recorded on unrecognized tax benefits and other income tax liabilities was immaterial for all periods presented. There were no accruals for penalties recorded in the Statements of Consolidated Income (Loss) for the years ended December 31, 2020, 2019 and 2018, and there were no balances for accrued penalties recorded on the Consolidated Balance Sheets as of December 31, 2020 and 2019. We are subject to income taxation in the United States and various state jurisdictions, primarily Indiana, Pennsylvania, Kentucky, Massachusetts, Maryland and Virginia.

Pension and Other Postretiremen

Pension and Other Postretirement Benefits	12 Months Ended
Pension and Other Postretirement Benefits	Dec. 31, 2020
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits We provide defined contribution plans and noncontributory defined benefit retirement plans that cover certain of our employees. Benefits under the defined benefit retirement plans reflect the employees’ compensation, years of service and age at retirement. Additionally, we provide health care and life insurance benefits for certain retired employees. The majority of employees may become eligible for these benefits if they reach retirement age while working for us. The expected cost of such benefits is accrued during the employees’ years of service. Current rates of rate-regulated companies include postretirement benefit costs, including amortization of the regulatory assets that arose prior to inclusion of these costs in rates. For most plans, cash contributions are remitted to grantor trusts. Our Pension and Other Postretirement Benefit Plans’ Asset Management . The Board has delegated oversight of the pension and other postretirement benefit plans’ assets to an Administrative & Investment Management Committee (“the Committee”). The Committee has adopted investment policy statements for the pension and other postretirement benefit plans’ assets. For the pension plans, we employ a liability-driven investing strategy. A total return approach is utilized for the other postretirement benefit plans’ assets. A mix of diversified investments are used to maximize the long-term return of plan assets and hedge the liabilities at a prudent level of risk. The investment portfolio includes U.S. and non-U.S. equities, real estate, long-term and intermediate-term fixed income and alternative investments. Risk tolerance is established through careful consideration of plan liabilities, funded status, and asset class volatility. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies. In determining the expected long-term rate of return on plan assets, historical markets are studied, relationships between equities and fixed income are analyzed and current market factors, such as inflation and interest rates are evaluated with consideration of diversification and rebalancing. Our expected long-term rate of return on assets is based on assumptions regarding target asset allocations and corresponding long-term capital market assumptions for each asset class. The pension plans’ investment policy calls for a gradual reduction in the allocation of return-seeking assets (equities, real estate and private equity) and a corresponding increase in the allocation of liability-hedging assets (fixed income) as the funded status of the plans’ increase. As of December 31, 2020, the asset mix and acceptable minimum and maximum ranges established by the policy for the pension and other postretirement benefit plans are as follows: Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 12% 32% 0% 55% International Equities 6% 16% 0% 25% Fixed Income 59% 71% 20% 100% Real Estate 0% 7% 0% 0% Private Equity 0% 5% 0% 0% Short-Term Investments 0% 10% 0% 10% As of December 31, 2019, the asset mix and acceptable minimum and maximum ranges established by the policy for the pension and other postretirement benefit plans were as follows: Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 12% 32% 0% 55% International Equities 6% 16% 0% 25% Fixed Income 59% 71% 20% 100% Real Estate 0% 7% 0% 0% Private Equity 0% 5% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2020 and December 31, 2019: Defined Benefit December 31, Postretirement December 31, Asset Class (in millions) Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 446.3 21.0 % $ 108.8 38.0 % International Equities 230.1 10.9 % 48.2 16.8 % Fixed Income 1,291.2 61.0 % 122.0 42.6 % Real Estate 52.9 2.5 % — — Cash/Other 97.2 4.6 % 7.4 2.6 % Total $ 2,117.7 100.0 % $ 286.4 100.0 % Defined Benefit Pension Assets December 31, Postretirement Benefit Plan Assets December 31, Asset Class (in millions) Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 446.4 21.5 % $ 93.8 35.9 % International Equities 205.0 9.9 % 40.7 15.6 % Fixed Income 1,337.2 64.2 % 119.5 45.7 % Real Estate 53.9 2.6 % — — Cash/Other 38.4 1.8 % 7.4 2.8 % Total $ 2,080.9 100.0 % $ 261.4 100.0 % The categorization of investments into the asset classes in the tables above are based on definitions established by our Benefits Committee. Fair Value Measurements. The following table sets forth, by level within the fair value hierarchy, the pension and other postretirement benefits investment assets at fair value as of December 31, 2020 and 2019. Assets are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. There were no investment assets in the pension and other postretirement benefits trusts classified within Level 3 for the years ended December 31, 2020 and 2019. Valuation Techniques Used to Determine Fair Value: Level 1 Measurements Most common and preferred stocks are traded in active markets on national and international securities exchanges and are valued at closing prices on the last business day of each period presented. Cash is stated at cost which approximates fair value, with the exception of cash held in foreign currencies which fluctuates with changes in the exchange rates. Short-term bills and notes are priced based on quoted market values. Level 2 Measurements Most U.S. Government Agency obligations, mortgage/asset-backed securities, and corporate fixed income securities are generally valued by benchmarking model-derived prices to quoted market prices and trade data for identical or comparable securities. To the extent that quoted prices are not available, fair value is determined based on a valuation model that includes inputs such as interest rate yield curves and credit spreads. Securities traded in markets that are not considered active are valued based on quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Other fixed income includes futures and options which are priced on bid valuation or settlement pricing. Level 3 Measurements Investments with unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities are classified as level 3 investments. Not Classified Commingled funds, private equity limited partnerships and real estate partnerships hold underlying investments that have prices derived from quoted prices in active markets and are not classified within the fair value hierarchy. Instead, these assets are measured at estimated fair value using the net asset value per share of the investments. Commingled funds' underlying assets are principally marketable equity and fixed income securities. Units held in commingled funds are valued at the unit value as reported by the investment managers. Private equity and real estate funds invest in natural resources, commercial real estate and distressed real estate. The fair value of these investments is determined by reference to the funds’ underlying assets. For the year ended December 31, 2020, there were no significant changes to valuation techniques to determine the fair value of our pension and other postretirement benefits' assets. Fair Value Measurements at December 31, 2020: (in millions) December 31, Quoted Prices in Active Markets for Significant Other Significant Pension plan assets: Cash $ 11.9 $ 11.9 $ — $ — Equity securities U.S. equities 2.4 2.4 — — Fixed income securities Government 243.4 — 243.4 — Corporate 692.6 — 692.6 — Mutual Funds U.S. multi-strategy 161.3 161.3 — — International equities 55.4 55.4 — — Fixed income 0.1 0.1 — — Private equity limited partnerships (3) U.S. multi-strategy (1) 10.9 — — — International multi-strategy (2) 6.6 — — — Distressed opportunities 0.3 — — — Real estate 52.9 — — — Commingled funds (3) Short-term money markets 78.8 — — — U.S. equities 279.7 — — — International equities 176.8 — — — Fixed income 337.6 — — — Pension plan assets subtotal 2,110.7 231.1 936.0 — Other postretirement benefit plan assets: Mutual funds U.S. multi-strategy 94.8 94.8 — — International equities 24.1 24.1 — — Fixed income 121.8 121.8 — — Commingled funds (3) Short-term money markets 7.6 — — — U.S. equities 14.0 — — — International equities 24.1 — — — Other postretirement benefit plan assets subtotal 286.4 240.7 — — Due to brokers, net (4) (1.6) — (1.6) — Accrued income/dividends 8.6 8.6 — — Total pension and other postretirement benefit plan assets $ 2,404.1 $ 480.4 $ 934.4 $ — (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2020: (in millions) Fair Value Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 86.4 Daily 1 day U.S. equities 293.7 Daily 1-5 days International equities 200.9 Monthly 10-30 days Fixed income 337.6 Daily 3 days Total $ 918.6 Fair Value Measurements at December 31, 2019: (in millions) December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Significant Pension plan assets: Cash $ 6.7 $ 6.7 $ — $ — Fixed income securities Government 319.6 — 319.6 — Corporate 651.8 — 651.8 — Mutual Funds U.S. multi-strategy 140.5 140.5 — — International equities 56.9 56.9 — — Private equity limited partnerships (3) U.S. multi-strategy (1) 14.0 — — — International multi-strategy (2) 8.5 — — — Distressed opportunities 0.5 — — — Real Estate 53.9 — — — Commingled funds (3) Short-term money markets 14.8 — — — U.S. equities 305.9 — — — International equities 148.1 — — — Fixed income 351.8 — — — Pension plan assets subtotal 2,073.0 204.1 971.4 — Other postretirement benefit plan assets: Mutual funds U.S. multi-strategy 81.7 81.7 — — International equities 20.6 20.6 — — Fixed income 119.2 119.2 — — Commingled funds (3) Short-term money markets 7.7 — — — U.S. equities 12.1 — — — International equities 20.1 — — — Other postretirement benefit plan assets subtotal 261.4 221.5 — — Due to brokers, net (4) (2.8) — (2.8) — Accrued income/dividends 10.7 10.7 — — Total pension and other postretirement benefit plan assets $ 2,342.3 $ 436.3 $ 968.6 $ — (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2019: Balance at January 1, 2019 Transfers out (Level 3) (1) Balance at December 31, 2019 Private equity limited partnerships U.S. multi-strategy 18.5 (18.5) — International multi-strategy 12.5 (12.5) — Distress opportunities 2.4 (2.4) — Real estate 52.7 (52.7) — Total $ 86.1 $ (86.1) $ — (1) Level 3 assets from 2018 were reclassified in the 2019 presentation and included within the fair value hierarchy table as of December 31, 2019 as "Not Classified" investments for which fair value is measured using net asset value per share, consistent with the definitions described above. The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2019: (in millions) Fair Value Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 22.5 Daily 1 day U.S. equities 318.0 Monthly 3 days International equities 168.2 Monthly 10-30 days Fixed income 351.8 Daily 3 days Total $ 860.5 Our Pension and Other Postretirement Benefit Plans’ Funded Status and Related Disclosure . The following table provides a reconciliation of the plans’ funded status and amounts reflected in our Consolidated Balance Sheets at December 31 based on a December 31 measurement date: Pension Benefits Other Postretirement Benefits (in millions) 2020 2019 2020 2019 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 2,130.5 $ 1,981.3 $ 576.5 $ 492.5 Service cost 32.0 29.2 6.6 5.1 Interest cost 51.6 72.3 15.4 19.2 Plan participants’ contributions — — 4.1 4.8 Plan amendments — — — 5.1 Actuarial loss (2) 140.1 204.3 24.8 88.8 Benefits paid (174.5) (156.6) (37.0) (39.5) Estimated benefits paid by incurred subsidy — — 0.4 0.5 Spinoff to Eversource (121.3) — — — Projected benefit obligation at end of year $ 2,058.4 $ 2,130.5 $ 590.8 $ 576.5 Change in plan assets Fair value of plan assets at beginning of year $ 2,080.9 $ 1,867.7 $ 261.4 $ 216.3 Actual return on plan assets 329.9 366.8 36.3 56.9 Employer contributions 2.9 2.9 21.6 23.0 Plan participants’ contributions — — 4.1 4.7 Benefits paid (174.6) (156.5) (37.0) (39.5) Spinoff to Eversource (121.4) — — — Fair value of plan assets at end of year $ 2,117.7 $ 2,080.9 $ 286.4 $ 261.4 Funded Status at end of year $ 59.3 $ (49.6) $ (304.4) $ (315.1) Amounts recognized in the statement of financial position consist of: Noncurrent assets 91.4 8.2 — — Current liabilities (2.9) (3.0) (0.9) (0.8) Noncurrent liabilities (29.2) (54.8) (303.5) (314.3) Net amount recognized at end of year (3) $ 59.3 $ (49.6) $ (304.4) $ (315.1) Amounts recognized in accumulated other comprehensive income or regulatory asset/liability (4) Unrecognized prior service credit $ 0.3 $ 3.0 $ (10.1) $ (10.7) Unrecognized actuarial loss 497.2 652.8 116.4 118.4 Net amount recognized at end of year $ 497.5 $ 655.8 $ 106.3 $ 107.7 (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in accumulated postretirement benefit obligation. (2) The pension actuarial loss was primarily driven by the decrease in the discount rate, offset by the change in mortality assumptions. The other postretirement benefits loss was also primarily driven by a decrease in discount rates, offset by favorable claims experienced and a change in the mortality assumptions. (3) We recognize our Consolidated Balance Sheets underfunded and overfunded status of our various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (3) We determined that for certain rate-regulated subsidiaries the future recovery of pension and other postretirement benefits costs is probable. These rate-regulated subsidiaries recorded regulatory assets and liabilities of $583.3 million and zero, respectively, as of December 31, 2020, and $739.1 million and $0.1 million, respectively, as of December 31, 2019 that would otherwise have been recorded to accumulated other comprehensive loss. Our accumulated benefit obligation for our pension plans was $2,036.8 million and $2,111.5 million as of December 31, 2020 and 2019, respectively. The accumulated benefit obligation at each date is the actuarial present value of benefits attributed by the pension benefit formula to employee service rendered prior to that date and based on current and past compensation levels. The accumulated benefit obligation differs from the projected benefit obligation disclosed in the table above in that it includes no assumptions about future compensation levels. We are required to reflect the funded status of our pension and postretirement benefit plans on the Consolidated Balance Sheet. The funded status of the plans is measured as the difference between the plan assets' fair value and the projected benefit obligation. We present the noncurrent aggregate of all underfunded plans within "Accrued liability for postretirement and postemployment benefits." The portion of the amount by which the actuarial present value of benefits included in the projected benefit obligation exceeds the fair value of plan assets, payable in the next 12 months, is reflected in "Accrued compensation and other benefits." We present the aggregate of all overfunded plans within "Deferred charges and other." Information for pension plans with a projected benefit obligation in excess of plan assets: December 31, 2020 (1) 2019 Accumulated Benefit Obligation $ 32.1 $ 1,473.9 Funded Status Projected Benefit Obligation 32.1 1,492.9 Fair Value of Plan Assets — 1,435.1 Funded Status of Underfunded Pension Plans at End of Year $ (32.1) $ (57.8) (1)As of December 31, 2020, only our nonqualified plans were underfunded. These plans have no assets as they are not funded until benefits are paid. Information for pension plans with plan assets in excess of the projected benefit obligation: December 31, 2020 2019 Accumulated Benefit Obligation $ 2,004.7 $ 637.6 Funded Status Projected Benefit Obligation 2,026.3 637.6 Fair Value of Plan Assets 2,117.7 645.8 Funded Status of Overfunded Pension Plans at End of Year $ 91.4 $ 8.2 Our pension plans were overfunded, in aggregate, by $59.3 million at December 31, 2020 compared to being underfunded by $49.6 million at December 31, 2019. The improvement in the funded status was due primarily to favorable asset returns offset by a decrease in discount rates. We contributed $2.9 million to our pension plans in both 2020 and 2019. Our other postretirement benefit plans were underfunded by $304.4 million at December 31, 2020 compared to being underfunded by $315.1 million at December 31, 2019. The change in funded status was primarily due to favorable asset returns offset by a decrease in discount rates. We contributed $21.6 million and $23.0 million to our other postretirement benefit plans in 2020 and 2019, respectively. In 2020 and 2019, some of our qualified pension plans paid lump sum payouts in excess of the respective plan's service cost plus interest cost, thereby meeting the requirement for settlement accounting. We recorded settlement charges of $10.5 million and $9.5 million in 2020 and 2019, respectively. Net periodic pension benefit cost for 2020 was decreased by $1.4 million as a result of the interim remeasurement. The following table provides the key assumptions that were used to calculate the pension and other postretirement benefits obligations for our various plans as of December 31: Pension Benefits Other Postretirement Benefits 2020 2019 2020 2019 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 2.38 % 3.12 % 2.49 % 3.21 % Rate of Compensation Increases 4.00 % 4.00 % — — Interest Crediting Rates 4.00 % 4.00 % — — Health Care Trend Rates Trend for Next Year — — 6.69 % 6.68 % Ultimate Trend — — 4.50 % 4.50 % Year Ultimate Trend Reached — — 2029 2028 We expect to make contributions of approximately $2.9 million to our pension plans and approximately $21.8 million to our postretirement medical and life plans in 2021. The following table provides benefits expected to be paid in each of the next five fiscal years, and in the aggregate for the five fiscal years thereafter. The expected benefits are estimated based on the same assumptions used to measure our benefit obligation at the end of the year and include benefits attributable to the estimated future service of employees: (in millions) Pension Benefits Other Federal Year(s) 2021 $ 218.8 $ 38.4 $ 0.4 2022 154.5 37.8 0.4 2023 149.2 37.3 0.4 2024 145.9 37.0 0.4 2025 141.3 36.6 0.3 2026-2030 621.9 172.1 1.2 The following table provides the components of the plans’ actuarially determined net periodic benefits cost for each of the three years ended December 31, 2020, 2019 and 2018: Pension Benefits Other Postretirement (in millions) 2020 2019 2018 2020 2019 2018 Components of Net Periodic Benefit Cost (1) Service cost $ 32.0 $ 29.2 $ 31.3 $ 6.6 $ 5.1 $ 5.0 Interest cost 51.6 72.3 67.1 15.4 19.2 17.6 Expected return on assets (111.6) (108.8) (142.3) (14.4) (13.1) (14.9) Amortization of prior service cost (credit) 0.7 0.2 (0.4) (2.1) (3.2) (4.0) Recognized actuarial loss 33.8 45.2 40.6 4.9 2.0 3.8 Settlement/curtailment loss 10.5 9.5 18.5 1.5 — — Total Net Periodic Benefits Cost $ 17.0 $ 47.6 $ 14.8 $ 11.9 $ 10.0 $ 7.5 (1) Service cost is presented in "Operation and maintenance" on the Statements of Consolidated Income (Loss). Non-service cost components are presented within "Other, net." The following table provides the key assumptions that were used to calculate the net periodic benefits cost for our various plans: Pension Benefits Other Postretirement 2020 2019 2018 2020 2019 2018 Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount rate - service cost 3.39 % 4.48 % 3.79 % 3.52 % 4.59 % 3.89 % Discount rate - interest cost 2.65 % 3.84 % 3.15 % 2.76 % 3.94 % 3.27 % Expected Long-Term Rate of Return on Plan Assets 5.70 % 6.10 % 7.00 % 5.67 % 5.83 % 5.80 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 % — — — Interest Crediting Rates 4.00 % 4.00 % 4.00 % — — — We assumed a 5.70% and 5.67% rate of return on pension and other postretirement plan assets, respectively, for our calculation of 2020 pension benefits cost. These rates were primarily based on asset mix and historical rates of return and were adjusted in 2020 due to anticipated changes in asset allocation and projected market returns. The following table provides other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory asset or liability: Pension Benefits Other Postretirement (in millions) 2020 2019 2020 2019 Other Changes in Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive Income or Regulatory Asset or Liability Net prior service cost $ — $ — $ — $ 5.1 Net actuarial loss (gain) (78.2) (53.8) 2.9 45.1 Settlements/curtailments (10.5) (9.5) (1.5) — Less: amortization of prior service cost (0.7) (0.2) 2.1 3.2 Less: amortization of net actuarial loss (33.8) (45.2) (4.9) (2.0) Less: gain attributable to spinoff to Eversource (33.1) — — — Less: prior service cost attributable to spinoff to Eversource (2.0) — — — Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability $ (158.3) $ (108.7) $ (1.4) $ 51.4 Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability $ (141.3) $ (61.1) $ 10.5 $ 61.4

Equity

Equity	12 Months Ended
Equity	Dec. 31, 2020
Equity [Abstract]
Equity	Equity Holders of shares of our common stock are entitled to receive dividends when, as and if declared by the Board out of funds legally available. The policy of the Board has been to declare cash dividends on a quarterly basis payable on or about the 20th day of February, May, August and November. We have certain debt covenants which could potentially limit the amount of dividends the Company could pay in order to maintain compliance with these covenants. Refer to Note 15, "Long-Term Debt," for more information. As of December 31, 2020, these covenants did not restrict the amount of dividends that were available to be paid. Dividends paid to preferred shareholders vary based on the series of preferred stock owned. Additional information is provided below. Holders of our shares of common stock are subject to the prior dividend rights of holders of our preferred stock or the depositary shares representing such preferred stock outstanding, and if full dividends have not been declared and paid on all outstanding shares of preferred stock in any dividend period, no dividend may be declared or paid or set aside for payment on our common stock. Common and preferred stock activity for 2020, 2019 and 2018 is described further below. ATM Program and Forward Sale Agreements. On May 3, 2017, we entered into four separate equity distribution agreements, pursuant to which we were able to sell up to an aggregate of $500.0 million of our common stock. On November 13, 2017, under the ATM program, we executed a forward agreement, which allowed us to issue a fixed number of shares at a price to be settled in the future. On November 6, 2018, the forward agreement was settled for $26.43 per share, resulting in $167.7 million of net proceeds. The equity distribution agreements entered into on May 3, 2017 expired December 31, 2018. On November 1, 2018, we entered into five separate equity distribution agreements pursuant to which we were able to sell up to an aggregate of $500.0 million of our common stock. Four of these agreements were then amended on August 1, 2019 and one was terminated, pursuant to which we may sell, from time to time, up to an aggregate of $434.4 million of our common stock. On December 6, 2018, under the ATM program, we executed a forward agreement, which allowed us to issue a fixed number of shares at a price to be settled in the future. From December 6, 2018 to December 10, 2018, 4,708,098 shares were borrowed from third parties and sold by the dealer at a weighted average price of $26.55 per share. On November 21, 2019, the forward agreement was settled for $26.01 per share, resulting in $122.5 million of net proceeds. On August 12, 2019, under the ATM program, we executed a forward agreement, which allowed us to issue a fixed number of shares at a price to be settled in the future. From August 12, 2019 to September 13, 2019, 3,714,400 shares were borrowed from third parties and sold by the dealer at a weighted average price of $29.26 per share. On December 11, 2019, the forward agreement was settled for $28.83 per share, resulting in $107.1 million of net proceeds. On August 6, 2020, under the ATM program, we executed a forward agreement, which allowed us to issue a fixed number of shares at a price to be settled in the future. From August 7, 2020 to September 3, 2020, 2,809,029 shares were borrowed from third parties and sold by the dealer at a weighted average price of $23.25 per share. On December 15, 2020, the forward agreement was settled for $22.77 per share, resulting in $64.0 million of net proceeds. On September 4, 2020, under the ATM program, we executed a separate forward agreement, which allowed us to issue a fixed number of shares at a price to be settled in the future. From September 4, 2020 to September 16, 2020, 1,452,102 shares were borrowed from third parties and sold by the dealer at a weighted average price of $22.28 per share. On December 15, 2020, the forward agreement was settled for $21.82 per share, resulting in $31.7 million of net proceeds. The equity distribution agreements entered into on November 1, 2018 and amended on August 1, 2019 expired December 31, 2020. The following table summarizes our activity under the ATM program: Year Ending December 31, 2020 2019 2018 Number of shares issued 8,459,430 8,422,498 8,883,014 Average price per share $ 23.60 $ 27.75 $ 26.85 Proceeds, net of fees ( in millions) $ 196.5 $ 229.1 $ 232.5 Private Placement of Common Stock. On May 4, 2018, we completed the sale of 24,964,163 shares of $0.01 par value common stock at a price of $24.28 per share in a private placement to selected institutional and accredited investors. The private placement resulted in $606.0 million of gross proceeds or $599.6 million of net proceeds, after deducting commissions and sale expenses. The common stock issued in connection with the private placement was registered on Form S-1, filed with the SEC on May 11, 2018. Preferred Stock. On June 11, 2018, we completed the sale of 400,000 shares of 5.650% Series A Fixed-Rate Reset Cumulative Redeemable Perpetual Preferred Stock (the "Series A Preferred Stock") at a price of $1,000 per share. The transaction resulted in $400.0 million of gross proceeds or $393.9 million of net proceeds, after deducting commissions and sale expenses. The Series A Preferred Stock was issued in a private placement pursuant to SEC Rule 144A. On December 13, 2018, we filed a registration statement with the SEC enabling holders to exchange their unregistered shares of Series A Preferred Stock for publicly registered shares with substantially identical terms. Dividends on the Series A Preferred Stock accrue and are cumulative from the date the shares of Series A Preferred Stock were originally issued to, but not including, June 15, 2023 at a rate of 5.650% per annum of the $1,000 liquidation preference per share. On and after June 15, 2023, dividends on the Series A Preferred Stock will accumulate for each five year period at a percentage of the $1,000 liquidation preference equal to the five-year U.S. Treasury Rate plus (i) in respect of each five year period commencing on or after June 15, 2023 but before June 15, 2043, a spread of 2.843% (the “Initial Margin”), and (ii) in respect of each five year period commencing on or after June 15, 2043, the Initial Margin plus 1.000%. The Series A Preferred Stock may be redeemed by us at our option on June 15, 2023, or on each date falling on the fifth anniversary thereafter, or in connection with a ratings event (as defined in the Certificate of Designation of the Series A Preferred Stock). As of December 31, 2020 and 2019, Series A Preferred Stock had $1.0 million of cumulative preferred dividends in arrears, or $2.51 per share. Holders of Series A Preferred Stock generally have no voting rights, except for limited voting rights with respect to (i) potential amendments to our certificate of incorporation that would have a material adverse effect on the existing preferences, rights, powers or duties of the Series A Preferred Stock, (ii) the creation or issuance of any security ranking on a parity with the Series A Preferred Stock if the cumulative dividends payable on then outstanding Series A Preferred Stock are in arrears, or (iii) the creation or issuance of any security ranking senior to the Series A Preferred Stock. The Series A Preferred Stock does not have a stated maturity and is not subject to mandatory redemption or any sinking fund. The Series A Preferred Stock will remain outstanding indefinitely unless repurchased or redeemed by us. Any such redemption would be effected only out of funds legally available for such purposes and will be subject to compliance with the provisions of our outstanding indebtedness. On December 5, 2018, we completed the sale of 20,000,000 depositary shares with an aggregate liquidation preference of $500,000,000 under the Company’s registration statement on Form S-3. Each depositary share represents 1/1,000th ownership interest in a share of our 6.500% Series B Fixed-Rate Reset Cumulative Redeemable Perpetual Preferred Stock, liquidation preference $25,000 per share (equivalent to $25 per depositary share) (the “Series B Preferred Stock"). The transaction resulted in $500.0 million of gross proceeds or $486.1 million of net proceeds, after deducting commissions and sale expenses. Dividends on the Series B Preferred Stock accrue and are cumulative from the date the shares of Series B Preferred Stock were originally issued to, but not including, March 15, 2024 at a rate of 6.500% per annum of the $25,000 liquidation preference per share. On and after March 15, 2024, dividends on the Series B Preferred Stock will accumulate for each five year period at a percentage of the $25,000 liquidation preference equal to the five-year U.S. Treasury Rate plus (i) in respect of each five year period commencing on or after March 15, 2024 but before March 15, 2044, a spread of 3.632% (the “Initial Margin”), and (ii) in respect of each five year period commencing on or after March 15, 2044, the Initial Margin plus 1.000%. The Series B Preferred Stock may be redeemed by us at our option on March 15, 2024, or on each date falling on the fifth anniversary thereafter, or in connection with a ratings event (as defined in the Certificate of Designation of the Series B Preferred Stock). As of December 31, 2020 and 2019, Series B Preferred Stock had $1.4 million of cumulative preferred dividends in arrears, or $72.23 per share. In addition, we issued 20,000 shares of “Series B-1 Preferred Stock”, par value $0.01 per share, (“Series B-1 Preferred Stock”), as a distribution with respect to the Series B Preferred Stock. As a result, each of the depositary shares issued on December 5, 2018 now represents a 1/1,000th ownership interest in a share of Series B Preferred Stock and a 1/1,000th ownership interest in a share of Series B-1 Preferred Stock. We issued the Series B-1 Preferred Stock to enhance the voting rights of the Series B Preferred Stock to comply with the minimum voting rights policy of the New York Stock Exchange. The Series B-1 Preferred Stock is paired with the Series B Preferred Stock and may not be transferred, redeemed or repurchased except in connection with the simultaneous transfer, redemption or repurchase of a like number of shares of the underlying Series B Preferred Stock. Holders of Series B Preferred Stock generally have no voting rights, except for limited voting rights with respect to (i) potential amendments to our certificate of incorporation that would have a material adverse effect on the existing preferences, rights, powers or duties of the Series B Preferred Stock, (ii) the creation or issuance of any security ranking on a parity with the Series B Preferred Stock if the cumulative dividends payable on then outstanding Series B Preferred Stock are in arrears, or (iii) the creation or issuance of any security ranking senior to the Series B Preferred Stock. In addition, if and whenever dividends on any shares of Series B Preferred Stock shall not have been declared and paid for at least six dividend periods, whether or not consecutive, the number of directors then constituting our Board of Directors shall automatically be increased by two until all accumulated and unpaid dividends on the Series B Preferred Stock shall have been paid in full, and the holders of Series B-1 Preferred Stock, voting as a class together with the holders of any outstanding securities ranking on a parity with the Series B-1 Preferred Stock and having like voting rights that are exercisable at the time and entitled to vote thereon, shall be entitled to elect the two additional directors. The Series B Preferred Stock does not have a stated maturity and is not subject to mandatory redemption or any sinking fund. The Series B Preferred Stock will remain outstanding indefinitely unless repurchased or redeemed by us. Any such redemption would be effected only out of funds legally available for such purposes and will be subject to compliance with the provisions of our outstanding indebtedness. The following table summarizes preferred stock by outstanding series of shares: Year ended December 31, December 31, December 31, 2020 2019 2018 2020 2019 (in millions except shares and per share amounts) Liquidation Preference Per Share Shares Dividends Declared Per Share Outstanding 5.650% Series A $ 1,000.00 400,000 $ 56.50 $ 56.50 $ 28.88 $ 393.9 $ 393.9 6.500% Series B $ 25,000.00 20,000 $ 1,625.00 $ 1,674.65 $ — $ 486.1 $ 486.1 Noncontrolling Interest in Consolidated Subsidiaries. In December 2020, NIPSCO and a tax equity partner completed their initial cash contributions into the Rosewater joint venture. Earnings, tax attributes and cash flows are allocated to both NIPSCO and the tax equity partner in varying percentages by category and over the life of the partnership. The tax equity partner's contributions, net of these allocations, is represented as a noncontrolling interest within total equity on the Consolidated Balance Sheets. Refer to Note 4, "Variable Interest Entities," for more information.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
Share-Based Compensation	Dec. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract]
Share-Based Compensation	Share-Based Compensation Prior to May 19, 2020 we issued share-based compensation to employees and non-employee directors under the NiSource Inc. 2010 Omnibus Plan ("2010 Omnibus Plan"), which was most recently approved by stockholders at the Annual Meeting of Stockholders held on May 12, 2015. The 2010 Omnibus Plan provided for awards to employees and non-employee directors of incentive and nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance units, cash-based awards and other stock-based awards and superseded the Director Stock Incentive Plan (“Director Plan”) with respect to grants made after the effective date of the 2010 Omnibus Plan. The stockholders approved and adopted the NiSource Inc. 2020 Omnibus Incentive Plan ("2020 Omnibus Plan") at the Annual Meeting of Stockholders held on May 19, 2020. The 2020 Omnibus Plan provides for awards to employees and non-employee directors of incentive and nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance units, cash-based awards and other stock-based awards and supersedes the 2010 Omnibus Plan with respect to grants made after the effective date of the 2020 Omnibus Plan. The 2020 Omnibus Plan provides that the number of shares of common stock of NiSource available for awards is 10,000,000 plus the number of shares subject to outstanding awards that expire or terminate for any reason that were granted under the 2020 Omnibus Plan, the 2010 Omnibus Plan or any other equity plan under which awards were outstanding as of May 19, 2020. At December 31, 2020, there were 10,007,832 shares available for future awards under the 2020 Omnibus Plan. We recognized stock-based employee compensation expense of $13.5 million, $16.3 million and $15.2 million, during 2020, 2019 and 2018, respectively, as well as related tax benefits of $3.3 million, $4.0 million and $3.7 million, respectively. We recognized related excess tax expense from the distribution of vested share-based employee compensation of $0.4 million in 2020 and excess tax benefits of $0.8 million and $1.0 million in 2019 and 2018, respectively. As of December 31, 2020, the total remaining unrecognized compensation cost related to non-vested awards amounted to $19.1 million, which will be amortized over the weighted-average remaining requisite service period of 1.9 years. Restricted Stock Units and Restricted Stock . We granted 235,100, 166,031, and 158,689 restricted stock units and shares of restricted stock to employees, subject to service conditions in 2020, 2019, and 2018, respectively. The total grant date fair value of the restricted stock units and shares of restricted stock during 2020, 2019, and 2018, respectively, was $6.1 million, $4.1 million, and $3.5 million based on the average market price of our common stock at the date of each grant less the present value of any dividends not received during the vesting period, which will be expensed over the vesting period which is generally three years. As of December 31, 2020, 223,724, 135,170, and 119,333 non-vested restricted stock units and shares of restricted stock granted in 2020, 2019, and 2018, respectively. If an employee terminates employment before the service conditions lapse under the 2018, 2019 or 2020 awards due to (1) retirement or disability (as defined in the award agreement), or (2) death, the service conditions will lapse on the date of such termination with respect to a pro rata portion of the restricted stock units and shares of restricted stock based upon the percentage of the service period satisfied between the grant date and the date of the termination of employment. In the event of a change in control (as defined in the award agreement), all unvested shares of restricted stock and restricted stock units awarded will immediately vest upon termination of employment occurring in connection with a change in control. Termination due to any other reason will result in all unvested shares of restricted stock and restricted stock units awarded being forfeited effective on the employee’s date of termination. A summary of our restricted stock unit award transactions for the year ended December 31, 2020 is as follows: (shares) Restricted Stock Weighted Average Non-vested at December 31, 2019 302,606 23.49 Granted 235,100 25.77 Forfeited (38,220) 24.18 Vested (21,259) 24.68 Non-vested at December 31, 2020 478,227 24.51 Employee Performance Shares . We granted 528,729 and 552,389 performance shares subject to service, performance and market-based vesting conditions in 2020 and 2019, respectively. We awarded 514,338 performance shares subject to similar service, performance and market conditions in 2018. The performance conditions are based on the achievement of one non-GAAP financial measure, relative total shareholder return and additional operational measures as outlined below. The financial measure is cumulative net operating earnings per share ("NOEPS"), which we define as income from continuing operations adjusted for certain items. The number of cumulative NOEPS shares determined using this measure shall be increased or decreased based on our relative total shareholder return, a market-based vesting condition, which we define as the annualized growth in dividends and share price of a share of our common stock (calculated using a 20 trading day average of our closing price over the performance period, approximately) compared to the total shareholder return of a predetermined peer group of companies. A relative shareholder return result within the first quartile will result in an increase to the NOEPS shares of 25%, while a relative shareholder return result within the fourth quartile will result in a decrease of 25%. A Monte Carlo analysis was used to value the portion of these awards dependent on the market-based vesting condition. The grant date fair value of the NOEPS shares is based on the average market price of our common stock at the date of each grant less the present value of dividends not received during the vesting period, which will be expensed over the requisite service period of three years. See table below for further details on these awards. If a threshold level of cumulative NOEPS financial performance is achieved, additional operational measures, which we refer to as the customer value framework and which consists of equally weighted areas of focus, apply. Each area of focus represents an equal portion of the customer value framework shares, and the targets for all areas of focus must be met for the customer value framework shares to vest at 100%. The grant date fair value of the customer value framework shares is based on the average market price of our common stock on the grant date of each award less the present value of dividends not received during the vesting period, which will be expensed over the requisite service period of three years for those customer value framework shares that are granted. See table below for further details on these awards. For the 2020 awards, the customer value framework consists of four equally weighted areas of focus including safety, customer satisfaction, culture and environmental, each representing 25% of the customer value framework shares. For the 2019 and 2018 awards, the customer value framework consists of five equally weighted areas of focus including financial and all those noted for the 2020 awards, each representing 20% of the customer value framework shares. For the 2018 awards, individual payout percentages for these shares may range from 0%-200% as determined by the compensation committee in its sole discretion. Due to this discretion, these shares are not considered to be granted under ASC 718. The service inception date fair value of the awards is based on the closing market price of our common stock on the service inception date of each award. This value will be reassessed at each reporting period to be based on our closing market price of our common stock at the reporting period date with adjustments to expense recorded as appropriate. The following table presents details of the performance awards described above. Award Year Service Conditions Lapse date Performance Period Award Conditions Shares outstanding at 12/31/2020 (shares) Grant Date Fair Value (in millions) 2020 02/28/23 01/01/2020- Non-GAAP Financial Measure 392,619 $ 11.7 Operational Measures 90,604 $ 2.6 2019 02/28/22 01/01/2019- Non-GAAP Financial Measure 384,680 $ 11.7 Operational Measures 88,769 $ 2.5 2018 02/26/21 01/01/2018- Non-GAAP Financial Measure 347,479 $ 9.2 Operational Measures (1) 80,185 $ 2.4 (1) Grant date fair value amount represents the service inception date fair value of these awards as they are not yet granted. A summary of our performance award transactions for the year ended December 31, 2020 is as follows: (shares) Performance Weighted Average Grant Date Fair Value Per Unit ($) (1) Non-vested at December 31, 2019 1,503,251 22.74 Granted 528,729 27.01 Forfeited (118,716) 25.63 Vested (528,928) 28.30 Non-vested at December 31, 2020 1,384,336 25.09 (1) 2018 performance shares awarded based on the customer value index are included at reporting date fair value as these awards have not been granted under ASC 718 as discussed above. Non-employee Director Awards . As of May 19, 2020, awards to non-employee directors may be made only under the 2020 Omnibus Plan. Currently, restricted stock units are granted annually to non-employee directors, subject to a non-employee director’s election to defer receipt of such restricted stock unit award. The non-employee director’s annual award of restricted stock units vest on the first anniversary of the grant date subject to special pro-rata vesting rules in the event of retirement or disability (as defined in the award agreement), or death. The vested restricted stock units are payable as soon as practicable following vesting except as otherwise provided pursuant to the non-employee director’s deferral election. Certain restricted stock units remain outstanding from the 2010 Omnibus Plan and the Director Plan. All such awards are fully vested and shall be distributed to the directors upon their separation from the Board. As of December 31, 2020, 210,273 restricted stock units are outstanding to non-employee directors under either the 2020 Omnibus Plan, the 2010 Omnibus Plan or the Director Plan. Of this amount, 67,806 restricted stock units are unvested and expected to vest. 401(k) Match, Profit Sharing and Company Contribution. We have a voluntary 401(k) savings plan covering eligible employees that allows for periodic discretionary matches as a percentage of each participant’s contributions payable in cash for nonunion employees and generally payable in shares of NiSource common stock for union employees, subject to collective bargaining. We also have a retirement savings plan that provides for discretionary profit sharing contributions similarly payable in cash or shares of NiSource common stock to eligible employees based on earnings results, and eligible employees hired after

Long-Term Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2020
Long-term Debt, Current and Noncurrent [Abstract]
Long-Term Debt	Long-Term Debt Our long-term debt as of December 31, 2020 and 2019 is as follows: Long-term debt type Maturity as of December 31, 2020 Weighted average interest rate (%) Outstanding balance as of December 31, (in millions) 2020 2019 Senior notes: NiSource December 2021 4.45 % — 63.6 NiSource November 2022 2.65 % — 500.0 NiSource February 2023 3.85 % — 250.0 NiSource June 2023 3.65 % — 350.0 NiSource August 2025 0.95 % 1,250.0 — NiSource November 2025 5.89 % — 265.0 NiSource May 2027 3.49 % 1,000.0 1,000.0 NiSource December 2027 6.78 % 3.0 3.0 NiSource September 2029 2.95 % 750.0 750.0 NiSource May 2030 3.60 % 1,000.0 — NiSource February 2031 1.70 % 750.0 — NiSource December 2040 6.25 % 152.6 250.0 NiSource June 2041 5.95 % 347.4 400.0 NiSource February 2042 5.80 % 250.0 250.0 NiSource February 2043 5.25 % 500.0 500.0 NiSource February 2044 4.80 % 750.0 750.0 NiSource February 2045 5.65 % 500.0 500.0 NiSource May 2047 4.38 % 1,000.0 1,000.0 NiSource March 2048 3.95 % 750.0 750.0 Total senior notes $ 9,003.0 $ 7,581.6 Medium term notes: NiSource April 2022 to May 2027 7.99 % $ 49.0 $ 49.0 NIPSCO August 2022 to August 2027 7.61 % 68.0 68.0 Columbia of Massachusetts (1) December 2025 to February 2028 6.37 % 15.0 40.0 Total medium term notes $ 132.0 $ 157.0 Finance leases: NiSource Corporate Services April 2022 to January 2025 2.19 % 49.4 22.3 NIPSCO November 2028 1.79 % 16.0 — Columbia of Ohio October 2021 to March 2044 6.16 % 91.2 94.8 Columbia of Virginia July 2029 to November 2039 6.30 % 18.4 19.1 Columbia of Kentucky May 2027 3.79 % 0.3 0.3 Columbia of Pennsylvania August 2027 to May 2035 5.65 % 19.7 20.7 Columbia of Massachusetts N/A — % — 44.3 Total finance leases 195.0 201.5 Unamortized issuance costs and discounts $ (86.9) $ (70.5) Total Long-Term Debt $ 9,243.1 $ 7,869.6 (1) Rate increased from 6.30% in 2019 to 6.37% in 2020 in connection with debt redemptions described below. Details of our 2020 long-term debt related activity are summarized below: • On April 13, 2020, we completed the issuance and sale of $1.0 billion of 3.60% senior unsecured notes maturing in 2030, which resulted in approximately $987.8 million of net proceeds after deducting commissions and expenses. • On August 18, 2020, we completed the issuance and sale of $1.25 billion of 0.95% senior unsecured notes maturing in 2025 and $750.0 million of 1.70% senior unsecured notes maturing in 2031, which resulted in approximately $1,980.4 million of net proceeds after deducting commissions and expenses. • In August 2020, we executed tender offers for $969.3 million of outstanding notes consisting of a combination of our 4.45% notes due 2021, 2.65% notes due 2022, 3.85% notes due 2023, 3.65% notes due 2023, 6.25% notes due 2040, and 5.95% notes due 2041. In August and September 2020, we redeemed $609.3 million of outstanding notes representing the remainder of our 4.45% notes due 2021, 2.65% notes due 2022, 3.85% notes due 2023, and 3.65% notes due 2023 and all of our 5.89% notes due 2025. In conjunction with the debt retired, we recorded a $231.8 million loss on early extinguishment of long-term debt, primarily attributable to early redemption premiums. • In September 2020, Columbia of Massachusetts redeemed $25.0 million of its outstanding 6.26% notes due 2028. In conjunction with the debt retired, Columbia of Massachusetts recorded an $11.7 million loss on early extinguishment of long-term debt, primarily attributable to early redemption premiums. Under the terms of the Asset Purchase Agreement, Columbia of Massachusetts’ net working capital at the closing of the sale of the Massachusetts Business was increased by 50% of the debt extinguishment costs, which was approximately $5.3 million. Details of our 2019 long-term debt related activity are summarized below: • On April 1, 2019, NIPSCO repaid $41.0 million of 5.85% pollution control bonds at maturity. • On August 12, 2019, we completed the issuance and sale of $750.0 million of 2.95% senior unsecured notes maturing in 2029 which resulted in approximately $742.4 million of net proceeds after deducting commissions and expenses. See Note 20-A, "Contractual Obligations," for the outstanding long-term debt maturities at December 31, 2020. Unamortized debt expense, premium and discount on long-term debt applicable to outstanding bonds are being amortized over the life of such bonds. We are subject to a financial covenant under our revolving credit facility which requires us to maintain a debt to capitalization ratio that does not exceed 70%. As of December 31, 2020, the ratio was 62.5%. We are also subject to certain other non-financial covenants under the revolving credit facility. Such covenants include a limitation on the creation or existence of new liens on our assets, generally exempting liens on utility assets, purchase money security interests, preexisting security interests and an additional subset of assets equal to $150 million. An asset sale covenant generally restricts the sale, conveyance, lease, transfer or other disposition of our assets to those dispositions that are for a price not materially less than fair market of such assets, that would not materially impair our ability to perform obligations under the revolving credit facility, and that together with all other such dispositions, would not have a material adverse effect. The covenant also restricts dispositions to no more than 10% of our consolidated total assets on December 31, 2015. The revolving credit facility also includes a cross-default provision, which triggers an event of default under the credit facility in the event of an uncured payment default relating to any indebtedness of us or any of our subsidiaries in a principal amount of $50.0 million or more. Our indentures generally do not contain any financial maintenance covenants. However, our indentures are generally subject to cross-default provisions ranging from uncured payment defaults of $5 million to $50 million, and limitations on the incurrence of liens on our assets, generally exempting liens on utility assets, purchase money security interests, preexisting security interests and an additional subset of assets capped at 10% of our consolidated net tangible assets.

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
Short-Term Borrowings	Dec. 31, 2020
Short-term Debt [Abstract]
Short-Term Borrowings	Short-Term BorrowingsWe generate short-term borrowings from our revolving credit facility, commercial paper program, accounts receivable transfer programs and now-settled term loan borrowings. Each of these borrowing sources is described further below. We maintain a revolving credit facility to fund ongoing working capital requirements, including the provision of liquidity support for our commercial paper program, provide for issuance of letters of credit and also for general corporate purposes. Our revolving credit facility has a program limit of $1.85 billion and is comprised of a syndicate of banks led by Barclays. On February 20, 2019, we extended the termination date of our revolving credit facility to February 20, 2024. At December 31, 2020 and 2019, we had no outstanding borrowings under this facility. Our commercial paper program has a program limit of up to $1.5 billion with a dealer group comprised of Barclays, Citigroup, Credit Suisse and Wells Fargo. We had $503.0 million and $570.0 million of commercial paper outstanding as of December 31, 2020 and 2019, respectively. Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term borrowings on the Consolidated Balance Sheets. We had no transfers as of December 31, 2020 and $353.2 million in transfers as of December 31, 2019, respectively. Refer to Note 19, "Transfers of Financial Assets," for additional information. On April 1, 2020, we terminated and repaid in full our existing $850.0 million term loan agreement with a syndicate of banks led by MUFG Bank, Ltd. and entered into a new $850.0 million term loan agreement with a syndicate of banks led by KeyBank National Association. Any and all outstanding borrowings under the term loan agreement were due by March 31, 2021. Interest charged on borrowings depended on the variable rate structure we elected at the time of each borrowing. The available variable rate structures from which we could choose were defined in the term loan agreement. Under the agreement, we borrowed $850.0 million on April 1, 2020 with an interest rate of LIBOR plus 75 basis points. On October 14, 2020, we terminated and repaid in full our $850.0 million term loan agreement with proceeds from the sale of the Massachusetts Business. Short-term borrowings were as follows: At December 31, (in millions) 2020 2019 Commercial Paper weighted-average interest rate of 0.27% and 2.03% at December 31, 2020 and 2019, respectively $ 503.0 $ 570.0 Accounts receivable securitization facility borrowings — 353.2 Term loan interest rate of 2.40% at December 31, 2019 — $ 850.0 Total Short-Term Borrowings $ 503.0 $ 1,773.2 Other than for the term loan, revolving credit facility and certain commercial paper borrowings, cash flows related to the borrowings and repayments of the items listed above are presented net in the Statements of Consolidated Cash Flows as their maturities are less than 90 days.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2020
Leases [Abstract]
Leases	Leases We adopted the provisions of ASC 842 beginning on January 1, 2019, using the transition method provided in ASU 2018-11, which was applied to all existing leases at that date. As such, results for reporting periods beginning after January 1, 2019 will be presented under ASC 842, while prior period amounts are reported in accordance with ASC 840. ASC 842 provides lessees the option of electing an accounting policy, by class of underlying asset, in which the lessee may choose not to separate nonlease components from lease components. We elected this practical expedient for our leases of fleet vehicles, IT assets and railcars. Adoption of this standard resulted in the recording of additional lease liabilities and corresponding ROU assets of $57.0 million on our Consolidated Balance Sheets as of January 1, 2019. The standard had no material impact on our Statements of Consolidated Income (Loss) or our Statements of Consolidated Cash Flows. Lease Descriptions. We are the lessee for substantially all of our leasing activity, which includes operating and finance leases for corporate and field offices, railcars, fleet vehicles and certain IT assets. Our corporate and field office leases have remaining lease terms between 1 and 23 years with options to renew the leases for up to 25 years. We lease railcars to transport coal to and from our electric generation facilities in Indiana. Our railcars are specifically identified in the lease agreements and have lease terms between 1 and 2 years with options to renew for 1 year. Our fleet vehicles include trucks, trailers and equipment that have been customized specifically for use in the utility industry. We lease fleet vehicles on 1 year terms, after which we have the option to extend on a month-to-month basis or terminate with written notice. ROU assets and liabilities on our Consolidated Balance Sheets do not include obligations for possible fleet vehicle lease renewals beyond the initial lease term. While we have the ability to renew these leases beyond the initial term, we are not reasonably certain (as that term is defined in ASC 842) to do so. We lease the majority of our IT assets under 4 year lease terms. Ownership of leased IT assets is transferred to us at the end of the lease term. We have not provided material residual value guarantees for our leases, nor do our leases contain material restrictions or covenants. Lease contracts containing renewal and termination options are mostly exercisable at our sole discretion. Certain of our real estate and railcar leases include renewal periods in the measurement of the lease obligation if we have deemed the renewals reasonably certain to be exercised. With respect to service contracts involving the use of assets, if we have the right to direct the use of the asset and obtain substantially all economic benefits from the use of an asset, we account for the service contract as a lease. Unless specifically provided to us by the lessor, we utilize NiSource's collateralized incremental borrowing rate commensurate to the lease term as the discount rate for all of our leases. Lease costs for the years ended December 31, 2020 and December 31, 2019 are presented in the table below. These costs include both amounts recognized in expense and amounts capitalized as part of the cost of another asset. Income statement presentation for these costs (when ultimately recognized on the income statement) is also included: Year Ended December 31, (in millions) Income Statement Classification 2020 2019 Finance lease cost Amortization of right-of-use assets Depreciation and amortization $ 23.4 $ 15.5 Interest on lease liabilities Interest expense, net 11.1 11.3 Total finance lease cost 34.5 26.8 Operating lease cost Operation and maintenance 20.3 17.9 Short-term lease cost Operation and maintenance — 1.0 Total lease cost $ 54.8 $ 45.7 Our right-of-use assets and liabilities are presented in the following lines on the Consolidated Balance Sheets: At December 31, (in millions) Balance Sheet Classification 2020 2019 Assets Finance leases Net Property, Plant and Equipment $ 176.8 $ 179.5 Operating leases Deferred charges and other 39.9 64.2 Total leased assets 216.7 243.7 Liabilities Current Finance leases Current portion of long-term debt 23.3 13.4 Operating leases Other accruals 10.3 13.2 Noncurrent Finance leases Long-term debt, excluding amounts due within one year 171.7 188.1 Operating leases Other noncurrent liabilities 29.9 51.6 Total lease liabilities $ 235.2 $ 266.3 Other pertinent information related to leases was as follows: Year Ended December 31, (in millions) 2020 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for finance leases $ 11.1 $ 11.3 Operating cash flows used for operating leases 20.2 17.9 Financing cash flows used for finance leases 18.4 10.6 Right-of-use assets obtained in exchange for lease obligations Finance leases 59.3 26.4 Operating leases $ 10.9 $ 13.4 December 31, 2020 December 31, 2019 Weighted-average remaining lease term (years) Finance leases 11.2 14.8 Operating leases 8.0 9.2 Weighted-average discount rate Finance leases 5.1 % 5.9 % Operating leases 4.0 % 4.3 % Maturities of our lease liabilities as of December 31, 2020 were as follows: As of December 31, 2020, (in millions) Total Finance Leases Operating Leases 2021 $ 44.4 $ 32.7 $ 11.7 2022 37.4 32.2 5.2 2023 33.5 28.8 4.7 2024 25.3 20.8 4.5 2025 19.8 16.1 3.7 Thereafter 152.3 134.1 18.2 Total lease payments 312.7 264.7 48.0 Less: Imputed interest (77.5) (69.7) (7.8) Total 235.2 195.0 40.2 Reported as of December 31, 2020 Short-term lease liabilities 33.6 23.3 10.3 Long-term lease liabilities 201.6 171.7 29.9 Total lease liabilities $ 235.2 $ 195.0 $ 40.2 There were no leases signed but not yet commenced as of December 31, 2020. Disclosures Related to Periods Prior to Adoption of ASC 842. We lease assets in several areas of our operations including fleet vehicles and equipment, rail cars for coal delivery and certain operations centers. Payments made in connection with operating leases were $49.1 million in 2018, and were primarily charged to operation and maintenance expense as incurred.

Fair Value

Fair Value	12 Months Ended
Fair Value	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value	Fair Value A. Fair Value Measurements Recurring Fair Value Measurements . The following tables present financial assets and liabilities measured and recorded at fair value on our Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2020 and December 31, 2019: Recurring Fair Value Measurements December 31, 2020 ( in millions ) Quoted Prices Significant Other Significant Balance as of December 31, 2020 Assets Risk management assets $ — $ 13.2 $ — $ 13.2 Available-for-sale securities — 170.9 — 170.9 Total $ — $ 184.1 $ — $ 184.1 Liabilities Risk management liabilities $ — $ 222.8 $ — $ 222.8 Total $ — $ 222.8 $ — $ 222.8 Recurring Fair Value Measurements December 31, 2019 ( in millions ) Quoted Prices Significant Other Significant Balance as of December 31, 2019 Assets Risk management assets $ — $ 4.4 $ — $ 4.4 Available-for-sale securities — 154.2 — 154.2 Total $ — $ 158.6 $ — $ 158.6 Liabilities Risk management liabilities $ — $ 146.6 $ — $ 146.6 Total $ — $ 146.6 $ — $ 146.6 Risk Management Assets and Liabilities. Risk management assets and liabilities include interest rate swaps, exchange-traded NYMEX futures and NYMEX options and non-exchange-based forward purchase contracts. When utilized, exchange-traded derivative contracts are based on unadjusted quoted prices in active markets and are classified within Level 1. These financial assets and liabilities are secured with cash on deposit with the exchange; therefore, nonperformance risk has not been incorporated into these valuations. Certain non-exchange-traded derivatives are valued using broker or over-the-counter, on-line exchanges. In such cases, these non-exchange-traded derivatives are classified within Level 2. Non-exchange-based derivative instruments include swaps, forwards, and options. In certain instances, these instruments may utilize models to measure fair value. We use a similar model to value similar instruments. Valuation models utilize various inputs that include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, other observable inputs for the asset or liability and market-corroborated inputs, (i.e., inputs derived principally from or corroborated by observable market data by correlation or other means). Where observable inputs are available for substantially the full term of the asset or liability, the instrument is categorized within Level 2. Certain derivatives trade in less active markets with a lower availability of pricing information and models may be utilized in the valuation. When such inputs have a significant impact on the measurement of fair value, the instrument is categorized within Level 3. Credit risk is considered in the fair value calculation of derivative instruments that are not exchange-traded. Credit exposures are adjusted to reflect collateral agreements that reduce exposures. As of December 31, 2020 and 2019, there were no material transfers between fair value hierarchies. Additionally, there were no changes in the method or significant assumptions used to estimate the fair value of our financial instruments. Credit risk is considered in the fair value calculation of each of our forward-starting interest rate swaps, as described in Note 10, "Risk Management Activities." As they are based on observable data and valuations of similar instruments, the hedges are categorized within Level 2 of the fair value hierarchy. There was no exchange of premium at the initial date of the swaps, and we can settle the contracts at any time. NIPSCO has entered into long-term forward natural gas purchase instruments to lock in a fixed price for its natural gas customers. We value these contracts using a pricing model that incorporates market-based information when available, as these instruments trade less frequently and are classified within Level 2 of the fair value hierarchy. For additional information see Note 10, “Risk Management Activities.” Available-for-Sale Debt Securities. Available-for-sale debt securities are investments pledged as collateral for trust accounts related to our wholly-owned insurance company. We value U.S. Treasury, corporate debt and mortgage-backed securities using a matrix pricing model that incorporates market-based information. These securities trade less frequently and are classified within Level 2. We adopted ASC 326 effective January 1, 2020. See "Recently Adopted Accounting Pronouncements" in Note 2, "Recent Accounting Pronouncements," for more information about ASC 326. Upon adoption of ASC 326, our available-for-sale debt securities impairments are recognized periodically using an allowance approach instead of an 'other than temporary' impairment model. At each reporting date, we utilize a quantitative and qualitative review process to assess the impairment of available-for-sale debt securities at the individual security level. For securities in a loss position, we evaluate our intent to sell or whether it is more-likely-than-not that we will be required to sell the security prior to the recovery of its amortized cost. If either criteria is met, the loss is recognized in earnings immediately, with the offsetting entry to the carrying value of the security. If both criteria are not met, we perform an analysis to determine whether the unrealized loss is related to credit factors. The analysis focuses on a variety of factors that include, but are not limited to, downgrade on ratings of the security, defaults in the current reporting period or projected defaults in the future, the security's yield spread over treasuries, and other relevant market data. If the unrealized loss is not related to credit factors, it is included in other comprehensive income. If the unrealized loss is related to credit factors, the loss is recognized as credit loss expense in earnings during the period, with an offsetting entry to the allowance for credit losses. The amount of the credit loss recorded to the allowance account is limited by the amount at which security's fair value is less than its amortized cost basis. If the credit losses in the allowance for credit losses are deemed uncollectible, the allowance on the uncollectible portion will be charged off, with an offsetting entry to the carrying value of the security. Subsequent improvements to the estimated credit losses of available-for-sale debt securities will be recognized immediately in earnings instead of over-time as they would under historic guidance. During the year ended December 31, 2020, we recorded $0.5 million as an allowance for credit losses on available-for-sale debt securities as a result of the analysis described above. Continuous credit monitoring and portfolio credit balancing mitigates our risk of credit losses on our available-for-sale debt securities. The amortized cost, gross unrealized gains and losses, allowance for credit losses, and fair value of available-for-sale securities at December 31, 2020 and 2019 were: December 31, 2020 (in millions) Amortized Gross Gross Unrealized Losses (1) Allowance for Credit Losses Fair Value Available-for-sale debt securities U.S. Treasury debt securities $ 33.7 $ 0.3 $ — $ — $ 34.0 Corporate/Other debt securities 130.2 7.7 (0.5) (0.5) 136.9 Total $ 163.9 $ 8.0 $ (0.5) $ (0.5) $ 170.9 December 31, 2019 (in millions) Amortized Gross Gross Unrealized Losses (2) Allowance for Credit Losses Fair Value Available-for-sale debt securities U.S. Treasury debt securities $ 31.4 $ 0.1 $ (0.1) $ — $ 31.4 Corporate/Other debt securities 118.7 4.2 (0.1) — 122.8 Total $ 150.1 $ 4.3 $ (0.2) $ — $ 154.2 (1) Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $0 and $13.2 million, respectively, at December 31, 2020. (2) Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $17.2 million and $12.2 million, respectively, at December 31, 2019. Realized gains and losses on available-for-sale securities were immaterial for the year-ended December 31, 2020 and 2019. The cost of maturities sold is based upon specific identification. At December 31, 2020, approximately $4.9 million of U.S. Treasury debt securities and approximately $4.3 million of Corporate/Other debt securities have maturities of less than a year. There are no material items in the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis for the years ended December 31, 2020 and 2019. Non-recurring Fair Value Measurements . We measure the fair value of certain assets on a non-recurring basis, typically annually or when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. These assets include goodwill and other intangible assets. The sale of the Massachusetts Business occurred on October 9, 2020, and the assets and liabilities of the Massachusetts Business were measured at fair value, less costs to sell. Our estimated total pre-tax loss for the year ended December 31, 2020 is $412.4 million. At December 31, 2019, we recorded an impairment charge of $204.8 million for goodwill and an impairment charge of $209.7 million for franchise rights, in each case related to Columbia of Massachusetts. For additional information, see Note 7, “Goodwill and Other Intangible Assets.” B. Other Fair Value Disclosures for Financial Instruments . The carrying amount of cash and cash equivalents, restricted cash, notes receivable, customer deposits and short-term borrowings is a reasonable estimate of fair value due to their liquid or short-term nature. Our long-term borrowings are recorded at historical amounts. The following method and assumptions were used to estimate the fair value of each class of financial instruments. Long-term debt . The fair value of outstanding long-term debt is estimated based on the quoted market prices for the same or similar securities. Certain premium costs associated with the early settlement of long-term debt are not taken into consideration in determining fair value. These fair value measurements are classified within Level 2 of the fair value hierarchy. For the years ended December 31, 2020 and 2019, there was no change in the method or significant assumptions used to estimate the fair value of long-term debt. The carrying amount and estimated fair values of these financial instruments were as follows: At December 31, (in millions) Carrying Amount 2020 Estimated Fair Value 2020 Carrying Amount 2019 Estimated Fair Value 2019 Long-term debt (including current portion) $ 9,243.1 $ 11,034.2 $ 7,869.6 $ 8,764.4

Transfers Of Financial Assets

Transfers Of Financial Assets	12 Months Ended
Transfers Of Financial Assets	Dec. 31, 2020
Transfers and Servicing [Abstract]
Transfers Of Financial Assets	Transfers of Financial Assets Columbia of Ohio, NIPSCO and Columbia of Pennsylvania each maintain a receivables agreement whereby they transfer their customer accounts receivables to third party financial institutions through wholly-owned and consolidated special purpose entities. The three agreements expire between May 2021 and October 2021 and may be further extended if mutually agreed to by the parties thereto. All receivables transferred to third parties are valued at face value, which approximates fair value due to their short-term nature. The amount of the undivided percentage ownership interest in the accounts receivables transferred is determined in part by required loss reserves under the agreements. Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term borrowings on the Consolidated Balance Sheets. As of December 31, 2020, the maximum amount of debt that could be recognized related to our accounts receivable programs is $380.0 million. The following table reflects the gross receivables balance and net receivables transferred as well as short-term borrowings related to the securitization transactions as of December 31, 2020 and 2019: At December 31, (in millions) 2020 2019 Gross receivables $ 607.7 $ 569.1 Less: receivables not transferred 607.7 215.9 Net receivables transferred $ — $ 353.2 Short-term debt due to asset securitization $ — $ 353.2 During 2020 and 2019, $353.2 million and $46.0 million, respectively, was recorded as cash flows used for financing activities related to the change in short-term borrowings due to securitization transactions. Fees associated with the securitization transactions were $2.6 million for the years ended December 31, 2020, 2019 and 2018. Columbia of Ohio, NIPSCO and Columbia of Pennsylvania remain responsible for collecting on the receivables securitized, and the receivables cannot be transferred to another party.

Other Commitments And Contingen

Other Commitments And Contingencies	12 Months Ended
Other Commitments And Contingencies	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Other Commitments And Contingencies	Other Commitments and Contingencies A. Contractual Obligations . We have certain contractual obligations requiring payments at specified periods. The obligations include long-term debt, lease obligations, energy commodity contracts and obligations for various services including pipeline capacity and outsourcing of IT services. The total contractual obligations in existence at December 31, 2020 and their maturities were: (in millions) Total 2021 2022 2023 2024 2025 After Long-term debt (1) $ 9,135.0 $ — $ 30.0 $ — $ — $ 1,260.0 $ 7,845.0 Interest payments on long-term debt 6,046.3 336.3 335.7 334.1 334.1 334.1 4,372.0 Finance leases (2) 264.7 32.7 32.2 28.8 20.8 16.1 134.1 Operating leases (3) 48.0 11.7 5.2 4.7 4.5 3.7 18.2 Energy commodity contracts 42.1 42.1 — — — — — Service obligations: Pipeline service obligations (4) 1,495.6 468.7 422.5 256.0 150.5 56.2 141.7 IT service obligations 240.3 74.9 74.0 38.1 30.5 22.8 — Other service obligations (5) 12.6 12.6 — — — — — Other liabilities (6) 116.9 26.0 0.8 90.1 — — — Total contractual obligations $ 17,401.5 $ 1,005.0 $ 900.4 $ 751.8 $ 540.4 $ 1,692.9 $ 12,511.0 (1) Long-term debt balance excludes unamortized issuance costs and discounts of $86.9 million. (2) Finance lease payments shown above are inclusive of interest totaling $69.7 million. (3) Operating lease payments shown above are inclusive of interest totaling $7.8 million. Operating lease balances do not include obligations for possible fleet vehicle lease renewals beyond the initial lease term. While we have the ability to renew these leases beyond the initial term, we are not reasonably certain (as that term is defined in ASC 842) to do so as they are renewed month-to-month after the first year. If we were to continue the fleet vehicle leases outstanding at December 31, 2020, payments would be $30.0 million in 2021, $27.7 million in 2022, $24.9 million in 2023, $22.0 million in 2024, $19.0 million in 2025 and $21.5 million thereafter. (4) In February 2021, the demand rate increased for our pipeline service obligations, resulting in a total increase of $638.6 million in addition to our future pipeline service obligations shown above. (5) On February 9, 2021, a rail transportation contract for the transportation of coal was fully executed between NIPSCO and a counterparty, replacing the prior agreement. The minimum coal tonnage shipment commitment for 2021 was eliminated under the new agreement, reducing our contractual obligation for 2021 by $12.1 million. (6) Other liabilities shown above are inclusive of the Rosewater Developer payment due in 2023. Purchase and Service Obligations. We have entered into various purchase and service agreements whereby we are contractually obligated to make certain minimum payments in future periods. Our purchase obligations are for the purchase of physical quantities of natural gas, electricity and coal. Our service agreements encompass a broad range of business support and maintenance functions which are generally described below. Our subsidiaries have entered into various energy commodity contracts to purchase physical quantities of natural gas, electricity and coal. These amounts represent the minimum quantity of these commodities we are obligated to purchase at both fixed and variable prices. To the extent contractual purchase prices are variable, obligations disclosed in the table above are valued at market prices as of December 31, 2020. NIPSCO has power purchase arrangements representing a total of 500 MW of wind power, with contracts expiring between between 2024 and 2040. No minimum quantities are specified within these agreements due to the variability of electricity generation from wind, so no amounts related to these contracts are included in the table above. Upon early termination of one of these agreements by NIPSCO for any reason (other than material breach by the counterparties), NIPSCO may be required to pay a termination charge that could be material depending on the events giving rise to termination and the timing of the termination. We have pipeline service agreements that provide for pipeline capacity, transportation and storage services. These agreements, which have expiration dates ranging from 2021 to 2038, require us to pay fixed monthly charges. NIPSCO has contracts with three major rail operators providing for coal transportation services for which there are certain minimum payments. These service contracts extend for various periods through 2021. We have executed agreements with multiple IT service providers. The agreements extend for various periods through 2025. B. Guarantees and Indemnities . We and certain subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries as part of normal business. Such agreements include guarantees and stand-by letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiaries’ intended commercial purposes. At December 31, 2020 and 2019, we had issued stand-by letters of credit of $15.2 million and $10.2 million , respectively, for the benefit of third parties. We have provided guarantees related to our future performance under BTAs for our renewable generation projects. At December 31, 2020, our guarantees for the Rosewater and Indiana Crossroads BTAs totaled $40.7 million. The amount of each guaranty will decrease upon the substantial completion of the construction of the facilities. See “- E. Other Matters - NIPSCO 2018 Integrated Resource Plan,” below for more information. C. Legal Proceedings . On September 13, 2018, a series of fires and explosions occurred in Lawrence, Andover and North Andover, Massachusetts related to the delivery of natural gas by Columbia of Massachusetts (the "Greater Lawrence Incident"). The Greater Lawrence Incident resulted in one fatality and a number of injuries, damaged multiple homes and businesses, and caused the temporary evacuation of significant portions of each municipality. The Massachusetts Governor’s Office declared a state of emergency, authorizing the Massachusetts DPU to order another utility company to coordinate the restoration of utility services in Lawrence, Andover and North Andover. The incident resulted in the interruption of gas for approximately 7,500 gas meters, the majority of which served residences and approximately 700 of which served businesses, and the interruption of other utility service more broadly in the area. Columbia of Massachusetts has replaced the cast iron and bare steel gas pipeline system in the affected area and restored service to nearly all of the gas meters. See “- E. Other Matters - Greater Lawrence Pipeline Replacement” below for more information. On September 1, 2020, the Massachusetts Governor terminated the state of emergency declared following the Greater Lawrence Incident. We have been subject to state and federal inquiries and investigations by government authorities and regulatory agencies regarding the Greater Lawrence Incident, including the Massachusetts DPU and the Massachusetts Attorney General's Office. On February 26, 2020, the Company and Columbia of Massachusetts entered into agreements with the U.S. Attorney’s Office for the District of Massachusetts to resolve the U.S. Attorney’s Office’s investigation relating to the Greater Lawrence Incident, as described below. The Company and Columbia of Massachusetts entered into an agreement with the Massachusetts Attorney General’s Office (among other parties) to resolve the Massachusetts DPU and the Massachusetts Attorney General’s Office investigations, that was approved by the Massachusetts DPU on October 7, 2020 as part of the sale of the Massachusetts Business to Eversource. NTSB Investigation . As previously disclosed, the NTSB concluded its investigation into the Greater Lawrence Incident. On November 24, 2020, the NTSB closed NiSource’s one remaining open safety recommendation. U.S. Department of Justice Investigation. On February 26, 2020, the Company and Columbia of Massachusetts entered into agreements with the U.S. Attorney’s Office to resolve the U.S. Attorney’s Office’s investigation relating to the Greater Lawrence Incident. Columbia of Massachusetts agreed to plead guilty in the United States District Court for the District of Massachusetts (the “Court”) to violating the Natural Gas Pipeline Safety Act (the “Plea Agreement”), and the Company entered into a Deferred Prosecution Agreement (the “DPA”). On March 9, 2020, Columbia of Massachusetts entered its guilty plea pursuant to the Plea Agreement, which the Court accepted. Subsequently, Columbia of Massachusetts and the U.S. Attorney’s Office modified the Plea Agreement. On June 23, 2020, the Court sentenced Columbia of Massachusetts in accordance with the terms of the modified Plea Agreement. Under the modified Plea Agreement, Columbia of Massachusetts is subject to the following terms, among others: (i) a criminal fine in the amount of $53,030,116, which has been paid; (ii) a three year probationary period that will terminate early upon a sale of Columbia of Massachusetts or a sale of its gas distribution business to a qualified third-party buyer consistent with certain requirements, but in no event before the end of the one-year mandatory period of probation; (iii) compliance with each of the NTSB recommendations stemming from the Greater Lawrence Incident; and (iv) employment of an in-house monitor until the end of the term of probation or until the sale of Columbia of Massachusetts or its gas distribution business, whichever is earlier. On October 13, 2020, the Court, upon agreement of the U.S. Attorney's Office and Columbia Gas of Massachusetts, modified the terms of probation by ending the term of the in-house monitor. Under the DPA, the U.S. Attorney’s Office agreed to defer prosecution of the Company in connection with the Greater Lawrence Incident for a three-year period (which three-year period may be extended for twelve (12) months upon the U.S. Attorney’s Office’s determination of a breach of the DPA) subject to certain obligations of the Company, including, but not limited to, the following: (i) the Company will use reasonable best efforts to sell Columbia of Massachusetts or Columbia of Massachusetts’ gas distribution business to a qualified third-party buyer consistent with certain requirements, and, upon the completion of any such sale, the Company will cease and desist any and all gas pipeline and distribution activities in the District of Massachusetts; (ii) the Company will forfeit and pay, within 30 days of the later of the sale becoming final or the date on which post-closing adjustments to the purchase price are finally determined in accordance with the agreement to sell Columbia of Massachusetts or its gas distribution business, a fine equal to the total amount of the profit or gain, if any, from any sale of Columbia of Massachusetts or its gas distribution business, with the amount of profit or gain determined as provided in the DPA; and (iii) the Company agrees as to each of the Company’s subsidiaries involved in the distribution of gas through pipeline facilities in Massachusetts, Indiana, Ohio, Pennsylvania, Maryland, Kentucky and Virginia to implement and adhere to each of the recommendations from the NTSB stemming from the Greater Lawrence Incident. Pursuant to the DPA, if the Company complies with all of its obligations under the DPA, including, but not limited to those identified above, the U.S. Attorney’s Office will not file any criminal charges against the Company related to the Greater Lawrence Incident. If Columbia of Massachusetts withdraws its plea for any reason, if the Court rejects any aspect of the Plea Agreement, or if Columbia of Massachusetts should fail to perform an obligation under the Plea Agreement prior to the sale of Columbia of Massachusetts or its gas distribution business, the U.S. Attorney's Office may, at its sole option, render the DPA null and void. The sale of the Massachusetts Business was completed on October 9, 2020. The Company was not required to forfeit or pay any funds because the Company did not realize a profit or gain from the sale as provided in the DPA. U.S. Federal Government Activity. On December 27, 2020, the Protecting Our Infrastructure of Pipelines and Enhancing Safety (PIPES) Act of 2020 was signed into law reauthorizing funding for federal pipeline safety programs through September 30, 2023. Among other things, the PIPES Act requires that PHMSA revise the pipeline safety regulations to require operators to update, as needed, their existing distribution integrity management plans, emergency response plans, and O&M plans. The PIPES Act also requires PHMSA to adopt new requirements for managing records and updating, as necessary existing district regulator stations to eliminate common modes of failure that can lead to overpressurization. PHMSA must also require that operators implement leak detection and repair programs that meet safety needs and consider the environment, require the use of advance leak detection practices and technologies, and require operators to be able to locate and categorize all leaks that are hazardous to human safety or the environment, or that can become hazardous. Natural gas companies, including the Company, may see increased costs depending on how PHMSA implements the new mandates resulting from the PIPES Act. Private Actions. Various lawsuits, including several purported class action lawsuits, have been filed by various affected residents or businesses in Massachusetts state courts against the Company and/or Columbia of Massachusetts in connection with the Greater Lawrence Incident. On July 26, 2019, the Company, Columbia of Massachusetts and NiSource Corporate Services Company, a subsidiary of the Company, entered into a term sheet with the class action plaintiffs under which they agreed to settle the class action claims in connection with the Greater Lawrence Incident. Columbia of Massachusetts agreed to pay $143 million into a settlement fund to compensate the settlement class and the settlement class agreed to release Columbia of Massachusetts and affiliates from all claims arising out of or related to the Greater Lawrence Incident. The following claims are not covered under the proposed settlement because they are not part of the consolidated class action: (1) physical bodily injury and wrongful death; (2) insurance subrogation, whether equitable, contractual or otherwise; and (3) claims arising out of appliances that are subject to the Massachusetts DPU orders. Emotional distress and similar claims are covered under the proposed settlement unless they are secondary to a physical bodily injury. The settlement class is defined under the term sheet as all persons and businesses in the three municipalities of Lawrence, Andover and North Andover, Massachusetts, subject to certain limited exceptions. The motion for preliminary approval and the settlement documents were filed on September 25, 2019. The preliminary approval court hearing was held on October 7, 2019 and the court issued an order granting preliminary approval of the settlement on October 11, 2019. The Court granted final approval of the settlement on March 12, 2020. With respect to claims not included in the consolidated class action, many of the asserted wrongful death and bodily injury claims have settled, and we continue to discuss potential settlements with remaining claimants. The outcomes and impacts of such private actions are uncertain at this time. Shareholder Derivative Lawsuit. On April 28, 2020, a shareholder derivative lawsuit was filed by the City of Detroit Police and Fire Retirement System in the United States District Court for the District of Delaware against certain of our current and former directors, alleging breaches of fiduciary duty with respect to the pipeline safety management systems relating to the distribution of natural gas prior to the Greater Lawrence Incident and also including claims related to our proxy statement disclosures regarding our safety systems. The remedies sought include damages for the alleged breaches of fiduciary duty, corporate governance reforms, and restitution of any unjust enrichment. The defendants have filed a motion to dismiss the lawsuit. The motion to dismiss is fully briefed. On January 5, 2021, the judge set the defendants’ motion to dismiss for oral argument on March 2, 2021. Because of the preliminary nature of this lawsuit, we are not able to estimate a loss or range of loss, if any, that may be incurred in connection with this matter at this time. Financial Impact. Since the Greater Lawrence Incident, we have recorded expenses of approximately $1,036 million for third-party claims and fines, penalties and settlements associated with government investigations. We estimate that total costs related to third-party claims and fines, penalties and settlements associated with government investigations resulting from the incident will range from $1,036 million to $1,050 million, depending on the number, nature, final outcome and value of third-party claims. With regard to third-party claims, these costs include, but are not limited to, personal injury and property damage claims, damage to infrastructure, business interruption claims, and mutual aid payments to other utilities assisting with the restoration effort. These costs do not include costs of certain third-party claims and fines, penalties or settlements associated with government investigations that we are not able to estimate. These costs also do not include non-claims related and government investigation-related legal expenses resulting from the incident, the capital cost of the pipeline replacement and the payment in lieu of penalties, which are set forth in " - D. Other Matters - Greater Lawrence Incident Restoration," "- Greater Lawrence Incident Pipeline Replacement," and Note 1-A, "Company Structure and Principles of Consolidation," respectively. The process for estimating costs associated with third-party claims relating to the Greater Lawrence Incident requires management to exercise significant judgment based on a number of assumptions and subjective factors. As more information becomes known, management’s estimates and assumptions regarding the financial impact of the Greater Lawrence Incident may change. The aggregate amount of third-party liability insurance coverage available for losses arising from the Greater Lawrence Incident is $800 million. We collected the entire $800 million as of December 31, 2019. Total expenses related to the incident have exceeded the total amount of insurance coverage available under our policies. Refer to "- E. Other Matters - Greater Lawrence Incident Restoration," below for a summary of third-party claims-related expense activity and associated insurance recoveries recorded since the Greater Lawrence Incident. We are also party to certain other claims, regulatory and legal proceedings arising in the ordinary course of business in each state in which we have operations, none of which is deemed to be individually material at this time. Due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim, proceeding or investigation related to the Greater Lawrence Incident or otherwise would not have a material adverse effect on our results of operations, financial position or liquidity. Certain matters in connection with the Greater Lawrence Incident have had or may have a material impact as described above. If one or more of such additional or other matters were decided against us, the effects could be material to our results of operations in the period in which we would be required to record or adjust the related liability and could also be material to our cash flows in the periods that we would be required to pay such liability. D. Environmental Matters . Our operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. We believe we are, in all material respects, in compliance with the environmental regulations currently applicable to our operations. It is management's continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. Management expects a significant portion of environmental assessment, improvement and remediation costs to be recoverable through rates for certain of our companies. As of December 31, 2020 and 2019, we had recorded a liability of $92.6 million and $104.4 million, respectively, to cover environmental remediation at various sites. The current portion of this liability is included in "Other Accruals" in the Consolidated Balance Sheets. The noncurrent portion is included in "Other noncurrent liabilities." We recognize costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated. The original estimates for remediation activities may differ materially from the amount ultimately expended. The actual future expenditures depend on many factors, including currently enacted laws and regulations, the nature and extent of impact and the method of remediation. These expenditures are not currently estimable at some sites. We periodically adjust our liability as information is collected and estimates become more refined. Electric Operations' compliance estimates disclosed below are reflective of NIPSCO's Integrated Resource Plan submitted to the IURC on October 31, 2018. See section " - E. Other Matters - NIPSCO 2018 Integrated Resource Plan," below for additional information. Air Future legislative and regulatory programs could significantly limit allowed GHG emissions or impose a cost or tax on GHG emissions. Additionally, rules that require further GHG reductions or impose additional requirements for natural gas facilities could impose additional costs. NiSource will carefully monitor all GHG reduction proposals and regulations. ACE Rule. On July 8, 2019, the EPA published the final ACE rule, which establishes emission guidelines for states to use when developing plans to limit carbon dioxide at coal-fired electric generating units based on heat rate improvement measures. The U.S. Court of Appeals for the D.C. Circuit vacated and remanded the rule on January 19, 2021. NIPSCO will continue to monitor this matter. Waste CERCLA. Our subsidiaries are potentially responsible parties at waste disposal sites under the CERCLA (commonly known as Superfund) and similar state laws. Under CERCLA, each potentially responsible party can be held jointly, severally and strictly liable for the remediation costs as the EPA, or state, can allow the parties to pay for remedial action or perform remedial action themselves and request reimbursement from the potentially responsible parties. Our affiliates have retained CERCLA environmental liabilities, including remediation liabilities, associated with certain current and former operations. These liabilities are not material to the Consolidated Financial Statements. MGP. A program has been instituted to identify and investigate former MGP sites where Gas Distribution Operations subsidiaries or predecessors may have liability. The program has identified 54 such sites where liability is probable. Remedial actions at many of these sites are being overseen by state or federal environmental agencies through consent agreements or voluntary remediation agreements. We utilize a probabilistic model to estimate our future remediation costs related to MGP sites. The model was prepared with the assistance of a third party and incorporates our experience and general industry experience with remediating MGP sites. We complete an annual refresh of the model in the second quarter of each fiscal year. No material changes to the estimated future remediation costs were noted as a result of the refresh completed as of June 30, 2020. Our total estimated liability related to the facilities subject to remediation was $85.0 million and $102.2 million at December 31, 2020 and 2019, respectively. The liability represents our best estimate of the probable cost to remediate the facilities. We believe that it is reasonably possible that remediation costs could vary by as much as $20 million in addition to the costs noted above. Remediation costs are estimated based on the best available information, applicable remediation standards at the balance sheet date, and experience with similar facilities. CCRs. On April 17, 2015, the EPA issued a final rule for regulation of CCRs. The rule regulates CCRs under the RCRA Subtitle D, which determines them to be nonhazardous. The rule is implemented in phases and requires increased groundwater monitoring, reporting, recordkeeping and posting of related information to the Internet. The rule also establishes requirements related to CCR management and disposal. The rule will allow NIPSCO to continue its byproduct beneficial use program. To comply with the rule, NIPSCO completed capital expenditures in 2019 to modify its infrastructure and manage CCRs. The CCR rule also resulted in revisions to previously recorded legal obligations associated with the retirement of certain NIPSCO facilities. The actual asset retirement costs related to the CCR rule may vary substantially from the estimates used to record the increased asset retirement obligation due to the uncertainty about the requirements that will be established by environmental authorities, compliance strategies that will be used and the preliminary nature of available data used to estimate costs. As allowed by the rule, NIPSCO will continue to collect data over time to determine the specific compliance solutions and associated costs and, as a result, the actual costs may vary. NIPSCO will also continue to work with EPA and the Indiana Department of Environmental Management to obtain administrative approvals associated with the CCR rule. In the event that the approvals are not obtained, future operations could be impacted. We believe the possibility of such an outcome is remote. E. Other Matters. NIPSCO 2018 Integrated Resource Plan. NIPSCO concluded in its October 2018 Integrated Resource Plan submission that NIPSCO’s current fleet of coal generation facilities will be retired earlier than previous Integrated Resource Plans had indicated. The Integrated Resource Plan evaluated demand-side and supply-side resource alternatives to reliably and cost effectively meet NIPSCO customers' future energy requirements over the ensuing 20 years. The preferred option within the Integrated Resource Plan retires the R.M. Schahfer Generating Station by mid-2023 and the Michigan City Generating Station by the end of 2028. These units represent 2,080 MW of generating capacity, equal to 72% of NIPSCO’s remaining generating capacity and 100% of NIPSCO's remaining coal-fired generating capacity. NIPSCO will refresh its 2018 Integrated Resource Plan in 2021. In the second quarter of 2020, the MISO approved NIPSCO's plan to retire the R.M. Schahfer Generating Station in 2023. In accordance with ASC 980-360, the net book value of certain plant and equipment for the R.M. Schahfer Generating Station was reclassified as "Non-Utility and Other" as described in Note 6, "Property, Plant and Equipment." The December 2019, NIPSCO electric rate case order included approval to create a regulatory asset upon the retirement of the R.M. Schahfer Generating Station. The order allows for the recovery of and on the net book value of the station by the end of 2032. Refer to Note 6, "Property, Plant and Equipment" for further information. In connection with the MISO's approval of NIPSCO's planned retirement of the R.M. Schahfer Generating Station, we recorded $4.6 million of plant retirement-related charges in the second quarter of 2020. These charges are presented within "Operation and maintenance" and were comprised of write downs of certain capital projects that have been cancelled and materials and supplies inventory balances deemed obsolete due to the planned retirement. As more information becomes available, the retirement date of the R.M. Schahfer Generating Station will be finalized, and additional plant retirement-related charges may be incurred. In February 2021, NIPSCO decided to submit modified Attachment Y Notices to MISO requesting accelerated retirement of two of the four coal fired units at R.M. Schahfer Generating Station. The two units are now expected to be retired by the end of 2021, with the remaining two units still scheduled to be retired in 2023. At retirement, the net book value of the retired units will be reclassified from "Non-Utility and Other property", to current and long-term “Regulatory Assets,” as described above. In connection with the planned retirement of the Schahfer Generating Station and the Michigan City Generating Station, the current capacity replacement plan includes lower-cost, reliable, cleaner energy resources to be obtained through a combination of NIPSCO ownership and PPAs. To this effect, NIPSCO has entered into a number of agreements with counterparties. NIPSCO has executed several PPAs to purchase 100% of the output from renewable generation facilities at a fixed price per MWh. Each facility supplying the energy will have an associated nameplate capacity, and payments under the PPAs will not begin until the associated generation facility is constructed by the owner/seller. NIPSCO has also executed several BTAs with developers to construct renewable generation facilities. NIPSCO's purchase requirement under the BTAs is dependent on satisfactory approval of the BTA by the IURC, successful execution of an agreement with a tax equity partner and timely completion of construction. NIPSCO and the tax equity partner are obligated to make cash contributions to the partnership at the date construction is substantially complete. Once the tax equity partner has earned their negotiated rate of return and we have reached the agreed upon contractual date, NIPSCO has the option to purchase at fair market value from the tax equity partner the remaining interest in the aforementioned joint venture. Greater Lawrence Incident Restoration . In addition to the amounts estimated for third-party claims and fines, penalties and settlements associated with government investigations described above, we have recorded expenses for other incident-related costs. Such costs include certain consulting costs, legal costs, vendor costs, claims center costs, labor and related expenses incurred in connection with the incident, and insurance-related loss surcharges. These amounts do not include the capital cost of the pipeline replacement, which is set forth below. The following table summarizes expenses incurred and insurance recoveries recorded since the Greater Lawrence Incident. This activity is presented within "Operation and maintenance" and "Other, net" in our Statements of Consolidated Income (Loss). Total Costs Incurred through Year Ended (in millions) December 31, 2019 December 31, 2020 Incident to Date Third-party claims and government fines, penalties and settlements $ 1,041 $ (5) $ 1,036 Other incident-related costs 420 22 442 Total 1,461 17 1,478 Insurance recoveries recorded (800) — (800) Total costs incurred $ 661 $ 17 $ 678 As discussed in "- C. Legal Proceedings," the aggregate amount of third-party liability insurance coverage available for losses arising from the Greater Lawrence Incident is $800 million. While we collected the entire $800 million, expenses related to the incident exceeded the total amount of insurance coverage available under our policies. The following table summarizes the total estimated incident-related expenses. (in millions) Current Total Estimated Amount Third-party claims and government fines, penalties and settlements $1,036 - $1,050 Other incident-related costs $445 - $450 Greater Lawrence Pipeline Replacement . In connection with the Greater Lawrence Incident, Columbia of Massachusetts, in cooperation with the Massachusetts Governor’s office, replaced the entire affected pipeline system. We invested approximately $258 million of capital spend for the pipeline replacement; this work was completed in 2019. We maintain property ins

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
Accumulated Other Comprehensive Loss	Dec. 31, 2020
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table displays the activity of Accumulated Other Comprehensive Loss, net of tax: (in millions) Gains and Losses on Securities (1) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Balance as of January 1, 2018 $ 0.2 $ (29.4) $ (14.2) $ (43.4) Other comprehensive income (loss) before reclassifications (3.0) 55.8 (4.4) 48.4 Amounts reclassified from accumulated other comprehensive loss 0.4 (33.1) — (32.7) Net current-period other comprehensive income (loss) (2.6) 22.7 (4.4) 15.7 Reclassification due to adoption of ASU 2018-02 — (6.3) (3.2) (9.5) Balance as of December 31, 2018 $ (2.4) $ (13.0) $ (21.8) $ (37.2) Other comprehensive income (loss) before reclassifications 6.1 (64.3) 2.3 (55.9) Amounts reclassified from accumulated other comprehensive loss (0.4) 0.1 0.8 0.5 Net current-period other comprehensive income (loss) 5.7 (64.2) 3.1 (55.4) Balance as of December 31, 2019 $ 3.3 $ (77.2) $ (18.7) $ (92.6) Other comprehensive income (loss) before reclassifications 3.3 (70.8) 2.9 (64.6) Amounts reclassified from accumulated other comprehensive loss (0.6) 0.1 1.0 0.5 Net current-period other comprehensive income (loss) 2.7 (70.7) 3.9 (64.1) Balance as of December 31, 2020 $ 6.0 $ (147.9) $ (14.8) $ (156.7) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net

Other, Net	12 Months Ended
Other, Net	Dec. 31, 2020
Other Nonoperating Income (Expense) [Abstract]
Other, Net	Other, Net Year Ended December 31, (in millions) 2020 2019 2018 Interest income $ 5.5 $ 7.7 $ 6.6 AFUDC equity 9.9 8.0 14.2 Charitable contributions (1) (1.5) (5.1) (45.3) Pension and other postretirement non-service cost (2) 9.3 (16.5) 18.0 Sale of emission reduction credits 4.6 — — Interest rate swap settlement gain (3) — — 46.2 Miscellaneous 4.3 0.7 3.8 Total Other, net $ 32.1 $ (5.2) $ 43.5 (1) 2018 charitable contributions include $20.7 million related to the Greater Lawrence Incident and $20.0 million of discretionary contributions made to the NiSource Charitable Foundation. See Note 20, "Other Commitments and Contingencies" for additional information on the Greater Lawrence Incident. (2) See Note 12, "Pension and Other Postretirement Benefits" for additional information. (3) See Note 10, "Risk Management Activities" for additional information.

Interest Expense, Net

Interest Expense, Net	12 Months Ended
Interest Expense, Net	Dec. 31, 2020
Interest Expense [Abstract]
Interest Expense, Net	Interest Expense, Net Year Ended December 31, (in millions) 2020 2019 2018 Interest on long-term debt $ 354.2 $ 327.7 $ 342.2 Interest on short-term borrowings 14.7 50.8 31.8 Debt discount/cost amortization 9.1 8.3 7.7 Accounts receivable securitization fees 2.6 2.6 2.6 Allowance for borrowed funds used and interest capitalized during construction (7.0) (7.5) (9.1) Debt-based post-in-service carrying charges (14.6) (18.7) (35.0) Other 11.7 15.7 13.1 Total Interest Expense, net $ 370.7 $ 378.9 $ 353.3

Segments Of Business

Segments Of Business	12 Months Ended
Segments Of Business	Dec. 31, 2020
Segment Reporting [Abstract]
Segments Of Business	Segments of Business At December 31, 2020, our operations are divided into two primary reportable segments, the Gas Distribution Operations and the Electric Operations segment. The remainder of our operations, which are not significant enough on a stand-alone basis to warrant treatment as an operating segment, are presented as "Corporate and Other" and primarily are comprised of interest expense on holding company debt, and unallocated corporate costs and activities. Refer to Note 3, "Revenue Recognition," for additional information on our segments and their sources of revenues. The following table provides information about our reportable segments. We use operating income as our primary measurement for each of the reported segments and make decisions on finance, dividends and taxes at the corporate level on a consolidated basis. Segment revenues include intersegment sales to affiliated subsidiaries, which are eliminated in consolidation. Affiliated sales are recognized on the basis of prevailing market, regulated prices or at levels provided for under contractual agreements. Operating income is derived from revenues and expenses directly associated with each segment. Year Ended December 31, (in millions) 2020 2019 2018 Operating Revenues Gas Distribution Operations Unaffiliated $ 3,128.1 $ 3,509.7 $ 3,406.4 Intersegment 12.1 13.1 13.1 Total 3,140.2 3,522.8 3,419.5 Electric Operations Unaffiliated 1,535.9 1,698.4 1,707.4 Intersegment 0.7 0.8 0.8 Total 1,536.6 1,699.2 1,708.2 Corporate and Other Unaffiliated 17.7 0.8 0.7 Intersegment 449.8 468.1 517.6 Total 467.5 468.9 518.3 Eliminations (462.6) (482.0) (531.5) Consolidated Operating Revenues $ 4,681.7 $ 5,208.9 $ 5,114.5 Year Ended December 31, (in millions) 2020 2019 2018 Operating Income (Loss) Gas Distribution Operations (1) $ 199.1 $ 675.4 $ (254.1) Electric Operations 348.8 406.8 386.1 Corporate and Other (2) 2.9 (191.5) (7.3) Consolidated Operating Income $ 550.8 $ 890.7 $ 124.7 Depreciation and Amortization Gas Distribution Operations $ 363.1 $ 403.2 $ 301.0 Electric Operations 321.3 277.3 262.9 Corporate and Other 41.5 36.9 35.7 Consolidated Depreciation and Amortization $ 725.9 $ 717.4 $ 599.6 Assets Gas Distribution Operations $ 13,433.0 $ 14,224.5 $ 13,527.0 Electric Operations 6,443.1 6,027.6 5,735.2 Corporate and Other 2,164.4 2,407.7 2,541.8 Consolidated Assets $ 22,040.5 $ 22,659.8 $ 21,804.0 Capital Expenditures (3) Gas Distribution Operations $ 1,266.9 $ 1,380.3 $ 1,315.3 Electric Operations 422.8 468.9 499.3 Corporate and Other 31.1 18.6 — Consolidated Capital Expenditures $ 1,720.8 $ 1,867.8 $ 1,814.6 (1) In 2020, Gas Distribution Operations reflects the loss of $412.4 million on the sale of the Massachusetts Business. For additional information, see Note 1, "Nature of Operations and Summary of Significant Accounting Policies". (2) In 2019, Corporate and Other reflects an impairment charge of $204.8 million for goodwill related to Columbia of Massachusetts. For additional information, see Note 7, "Goodwill and Other Intangible Assets." (3) Amounts differ from those presented on the Statements of Consolidated Cash Flows primarily due to the inclusion of capital expenditures in current liabilities, the capitalized portion of the Corporate Incentive Plan payout, and AFUDC Equity.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
Quarterly Financial Data	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) Quarterly financial data does not always reveal the trend of our business operations due to nonrecurring items and seasonal weather patterns, which affect earnings and related components of revenue and operating income. (in millions, except per share data) First Quarter (1) Second Quarter (2) Third Quarter (3) Fourth Quarter (4) 2020 Operating Revenues $ 1,605.5 $ 962.7 $ 902.5 $ 1,211.0 Operating Income 148.2 91.7 92.8 218.1 Net Income (Loss) 75.6 (4.7) (172.9) 87.8 Net income attributable to noncontrolling interest — — — 3.4 Net Income (Loss) attributable to NiSource 75.6 (4.7) (172.9) 84.4 Preferred Dividends (13.8) (13.8) (13.8) (13.7) Net Income (Loss) Available to Common Shareholders 61.8 (18.5) (186.7) 70.7 Earnings (Loss) Per Share Basic Earnings (Loss) Per Share $ 0.16 $ (0.05) $ (0.49) $ 0.18 Diluted Earnings (Loss) Per Share $ 0.16 $ (0.05) $ (0.49) $ 0.18 2019 Operating Revenues $ 1,869.8 $ 1,010.4 $ 931.5 $ 1,397.2 Operating Income (Loss) 374.2 463.5 91.0 (38.0) Net Income (Loss) 218.9 296.9 6.6 (139.3) Preferred Dividends (13.8) (13.8) (13.8) (13.7) Net Income (Loss) Available to Common Shareholders 205.1 283.1 (7.2) (153.0) Earnings (Loss) Per Share Basic Earnings (Loss) Per Share $ 0.55 $ 0.76 $ (0.02) $ (0.41) Diluted Earnings (Loss) Per Share $ 0.55 $ 0.75 $ (0.02) $ (0.41) (1) Net income for the first quarter of 2020 was impacted by $280.2 million loss on sale of the Massachusetts Business. Net income for the first quarter of 2019 was impacted by $108.0 million in insurance recoveries (pretax) related to the Greater Lawrence Incident. See Note 1, "Company Structure and Principles of Consolidation" and Note 20-E, "Other Matters" for additional information. (2) Net income for the second quarter of 2020 was impacted by an additional $84.4 million loss on sale of the Massachusetts Business. Net income for the second quarter of 2019 was impacted by $297.0 million in insurance recoveries (pretax) related to the Greater Lawrence Incident. See Note 1, "Company Structure and Principles of Consolidation" and Note 20-E, "Other Matters" for additional information. (3) Net loss for the third quarter of 2020 was impacted by $243.4 million loss on early extinguishments of long-term debt. See Note 15, "Long-Term Debt" for additional information.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
Supplemental Cash Flow Information	Dec. 31, 2020
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following table provides additional information regarding our Consolidated Statements of Cash Flows for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, (in millions) 2020 2019 2018 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities $ 170.4 $ 223.6 $ 152.0 Assets acquired under a finance lease 59.3 26.4 54.6 Assets acquired under an operating lease 10.9 13.4 — Reclassification of other property to regulatory assets (1) — — 245.3 Assets recorded for asset retirement obligations (2) 91.5 54.6 78.1 Obligation to developer at formation of joint venture (3) 69.7 — — Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 349.0 $ 349.7 $ 354.2 Cash paid for income taxes, net of refunds (4) (1.0) 10.8 3.3 (1) See Note 9 "Regulatory Matters" for additional information. (2) See Note 8 "Asset Retirement Obligations" for additional information. (3) Represents investing non-cash activity. See Note 4 "Variable Interest Entities" for additional information. (4) Amount of refunds in 2020 was greater than the amount of tax payments due to overpayments in 2019.

Nature of Operations And Summ_2

Nature of Operations And Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Structure And Principles Of Consolidation	Company Structure and Principles of Consolidation. We are an energy holding company incorporated in Delaware and headquartered in Merrillville, Indiana. Our subsidiaries are fully regulated natural gas and electric utility companies serving approximately 3.7 million customers in six states. We generate substantially all of our operating income through these rate-regulated businesses. The consolidated financial statements include the accounts of us, our majority-owned subsidiaries, and VIEs of which we are the primary beneficiary after the elimination of all intercompany accounts and transactions. On February 26, 2020, NiSource and Columbia of Massachusetts entered into an Asset Purchase Agreement with Eversource (the "Asset Purchase Agreement"). On October 9, 2020, NiSource and Columbia of Massachusetts received net proceeds from the sale of approximately $1,113 million, which included, a $1,100 million purchase price, an estimate of Columbia of Massachusetts' net working capital, net of closing costs and a $56.0 million payment in lieu of penalties that NiSource agreed to make in full settlement of all of the pending and potential claims, lawsuits, investigations or proceedings settled by and released by a settlement agreement approved by the Massachusetts DPU. As of December 31, 2020, we have recorded a loss on the sale of $412.4 million based on asset and liability balances as of the close of the transaction on October 9, 2020, estimated net working capital and estimated transaction costs. This estimated pre-tax loss is presented as "Loss on sale of assets, net" on the Statements of Consolidated Income (Loss) and is subject to change based on the final net working capital determination. The Massachusetts Business had the following pretax income (loss) for the twelve months ended December 31, 2020, 2019 and 2018: Twelve Months Ended (in millions) 2020 2019 2018 Pretax Income (Loss) ($422.3) $36.8 ($835.6) We continue to monitor how the COVID-19 pandemic is affecting our workforce, customers, suppliers, operations, financial results and cash flow. See Note 3, "Revenue Recognition," Note 9, "Regulatory Matters," and Note 11, "Income Taxes," for information on the pandemic.
Use Of Estimates	Use of Estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash, Cash Equivalents, And Restricted Cash	Cash, Cash Equivalents and Restricted Cash. We consider all highly liquid investments with original maturities of three months or less to be cash equivalents. We report amounts deposited in brokerage accounts for margin requirements as restricted cash. In addition, we have amounts deposited in trust to satisfy requirements for the provision of various property, liability, workers compensation, and long-term disability insurance, which is classified as restricted cash on the Consolidated Balance Sheets and disclosed with cash and cash equivalents on the Statements of Consolidated Cash Flows.
Accounts Receivable And Unbilled Revenue	Accounts Receivable and Unbilled Revenue. Accounts receivable on the Consolidated Balance Sheets includes both billed and unbilled amounts. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the last cycle billing date through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates, weather and reasonable and supportable forecasts. Accounts receivable fluctuates from year to year depending in large part on weather impacts and price volatility. Our accounts receivable on the Consolidated Balance Sheets include unbilled revenue, less reserves, in the amounts of $338.3 million and $350.5 million as of December 31, 2020 and 2019, respectively. The reserve for uncollectible receivables is our best estimate of the amount of probable credit losses in the existing accounts receivable. We determined the reserve based on historical experience and in consideration of current market conditions. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered. Refer to Note 3, "Revenue Recognition," for additional information on customer-related accounts receivable.
Investments In Debt And Equity Securities	Investments in Debt Securities. Our investments in debt securities are carried at fair value and are designated as available-for-sale. These investments are included within “Other investments” on the Consolidated Balance Sheets. Unrealized gains and losses, net of deferred income taxes, are recorded to accumulated other comprehensive income or loss. These investments are monitored for other than temporary declines in market value. Realized gains and losses and permanent impairments are reflected in the Statements of Consolidated Income (Loss). No material impairment charges were recorded for the years ended December 31, 2020, 2019 or 2018. Refer to Note 18, "Fair Value," for additional information.
Basis Of Accounting For Rate-Regulated Subsidiaries	Basis of Accounting for Rate-Regulated Subsidiaries. Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are later recognized in income as the related amounts are included in customer rates and recovered from or refunded to customers.We continually evaluate whether or not our operations are within the scope of ASC 980 and rate regulations. As part of that analysis, we evaluate probability of recovery for our regulatory assets. In management’s opinion, our regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Refer to Note 9, "Regulatory Matters," for additional information.
Utility Plant And Other Property And Related Depreciation And Maintenance	Plant and Other Property and Related Depreciation and Maintenance. Property, plant and equipment (principally utility plant) is stated at cost. Our rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the electric, gas and common properties, as approved by the appropriate regulators. Non-utility property includes renewable generation assets owned by a joint venture of which we are the primary beneficiary and is generally depreciated on a straight-line basis over the life of the associated asset. Refer to Note 6, "Property, Plant and Equipment," for additional information related to depreciation expense. For rate-regulated companies, AFUDC is capitalized on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. Our pre-tax rate for AFUDC was 2.6% in 2020, 3.0% in 2019 and 3.5% in 2018. Generally, our subsidiaries follow the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When our subsidiaries retire regulated property, plant and equipment, original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable a regulated asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the gross amounts are classified as "Non-Utility and Other " as described in Note 6, "Property, Plant and Equipment." If the asset is no longer operating but still subject to recovery, the net amount is classified in "Regulatory assets" on the Consolidated Balance Sheets. If we are able to recover a full return of and on investment, the carrying value of the asset is based on historical cost. If we are not able to recover a full return on investment, a loss on impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When our subsidiaries sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from "Net Property, Plant and Equipment" on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. Refer to Note 6, "Property, Plant and Equipment," for further information. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years
Goodwill And Other Intangible Assets	Goodwill and Other Intangible Assets. Substantially all of our goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. We test our goodwill for impairment annually as of May 1, or more frequently if events and circumstances indicate that goodwill might be impaired. Fair value of our reporting units is determined using a combination of income and market approaches. See Note 7, "Goodwill and Other Intangible Assets," for additional information.
Accounts Receivable Transfer Program	Accounts Receivable Transfer Program. Certain of our subsidiaries have agreements with third parties to transfer certain accounts receivable without recourse. These transfers of accounts receivable are accounted for as secured borrowings. The entire gross receivables balance remains on the December 31, 2020 and 2019 Consolidated Balance Sheets and short-term debt is recorded in the amount of proceeds received from the transferees involved in the transactions. Refer to Note 19, "Transfers of Financial Assets," for further information.
Fuel Adjustment Clause	Gas Cost and Fuel Adjustment Clause. Our regulated subsidiaries defer most differences between gas and fuel purchase costs and the recovery of such costs in revenues and adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. These deferred balances are recorded as "Regulatory assets" or "Regulatory liabilities," as appropriate, on the Consolidated Balance Sheets. Refer to Note 9, "Regulatory Matters," for additional information.
Gas Inventory	Inventory. Both the LIFO inventory methodology and the weighted average cost methodology are used to value natural gas in storage, as approved by regulators for all of our regulated subsidiaries. Inventory valued using LIFO was $42.3 million and $47.2 million at December 31, 2020 and 2019, respectively. Based on the average cost of gas using the LIFO method, the estimated replacement cost of gas in storage was less than the stated LIFO cost by $19.6 million and $25.5 million at December 31, 2020 and 2019, respectively. Gas inventory valued using the weighted average cost methodology was $148.8 million at December 31, 2020 and $203.7 million at December 31, 2019.Electric production fuel is valued using the weighted average cost inventory methodology, as approved by NIPSCO's regulator. Materials and supplies are valued using the weighted average cost inventory methodology.
Accounting For Exchange And Balancing Arrangements Of Natural Gas	Accounting for Exchange and Balancing Arrangements of Natural Gas. Our Gas Distribution Operations segment enters into balancing and exchange arrangements of natural gas as part of its operations and off-system sales programs. We record a receivable or payable for any of our respective cumulative gas imbalances, as well as for any gas inventory borrowed or lent under a Gas Distribution Operations exchange agreement. Exchange gas is valued based on individual regulatory jurisdiction requirements (for example, historical spot rate, spot at the beginning of the month). These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on our Consolidated Balance Sheets, as appropriate.
Accounting For Risk Management Activities	Accounting for Risk Management Activities. We account for our derivatives and hedging activities in accordance with ASC 815. We recognize all derivatives as either assets or liabilities on the Consolidated Balance Sheets at fair value, unless such contracts are exempted as a normal purchase normal sale under the provisions of the standard. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation. We have elected not to net fair value amounts for any of our derivative instruments or the fair value amounts recognized for the right to receive cash collateral or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. See Note 10, "Risk Management Activities," for additional information.
Income Taxes And Investment Tax Credits	Income Taxes and Investment Tax Credits. We record income taxes to recognize full interperiod tax allocations. Under the asset and liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amount and the tax basis of existing assets and liabilities. Investment tax credits associated with regulated operations are deferred and amortized as a reduction to income tax expense over the estimated useful lives of the related properties.
Environmental Expenditures	Environmental Expenditures. We accrue for costs associated with environmental remediation obligations, including expenditures related to asset retirement obligations and cost of removal, when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The accruals for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Other accruals” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. Rate-regulated subsidiaries applying regulatory accounting establish regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Refer to Note 8, "Asset Retirement Obligations," and Note 20, "Other Commitments and Contingencies," for further information.
Excise Taxes	Excise Taxes. As an agent for some state and local governments, we invoice and collect certain excise taxes levied by state and local governments on customers and record these amounts as liabilities payable to the applicable taxing jurisdiction. Such balances are presented within "Other accruals" on the Consolidated Balance Sheets. These types of taxes collected from customers, comprised largely of sales taxes, are presented on a net basis affecting neither revenues nor cost of sales. We account for excise taxes for which we are liable by recording a liability for the expected tax with a corresponding charge to “Other taxes” expense on the Statements of Consolidated Income (Loss).
Accrued Insurance Liabilities	Accrued Insurance Liabilities. We accrue for insurance costs related to workers compensation, automobile, property, general and employment practices liabilities based on the most probable value of each claim. In general, claim values are determined by professional, licensed loss adjusters who consider the facts of the claim, anticipated indemnification and legal expenses, and respective state rules. Claims are reviewed by us at least quarterly and an adjustment is made to the accrual based on the most current information. Refer to Note 20-E "Other Matters" for further information on accrued insurance liabilities related to the Greater Lawrence Incident.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
Accounting Policies (Tables)	Dec. 31, 2020
Accounting Policies [Abstract]
Disposal Groups, Pretax Income (Loss)	The Massachusetts Business had the following pretax income (loss) for the twelve months ended December 31, 2020, 2019 and 2018: Twelve Months Ended (in millions) 2020 2019 2018 Pretax Income (Loss) ($422.3) $36.8 ($835.6)

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Tables)	12 Months Ended
Recent Accounting Pronouncements (Tables)	Dec. 31, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	Recently Issued Accounting Pronouncements We are currently evaluating the impact of certain ASUs on our Consolidated Financial Statements or Notes to Consolidated Financial Statements, which are described below: Standard Description Effective Date Effect on the financial statements or other significant matters ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Statement This pronouncement provides Upon issuance on We continue to evaluate the temporary expedients and options available under this guidance, and the effects of these pronouncements on our Consolidated Financial Statements and Notes to Consolidated Financial Statements. We are currently identifying and evaluating contracts that may be impacted. As of December 31, 2020, we have not applied any expedients and options available under this ASU. ASU 2021-01, Reference Rate Reform (Topic 848): Scope Standard Description Effective Date Effect on the financial statements or other significant matters ASU 2020-06, Debt with Conversion and Other Options (Subtopic 470-20) and Derivative and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity's Own Equity This pronouncement simplifies Annual period This pronouncement does not impact any securities we currently have on our balance sheet. We will continue to
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]	Recently Adopted Accounting Pronouncements Standard Adoption ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (ASC 326). ASC 326 revised the GAAP guidance on the impairment of most financial assets and certain other instruments that are not measured at fair value through net income. ASC 326 introduces the current expected credit loss (CECL) model that is based on expected losses for ASU 2016-13, Financial Instruments-Credit Losses (Topic 326) ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans Issued in August 2018, the pronouncement modifies the disclosure requirements for defined benefit pension or other postretirement benefit plans. The guidance removes disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and adds disclosure requirements identified as relevant. The modifications affect annual period disclosures for fiscal years ending after December 15, 2020, and are applied on a retrospective basis to all periods presented. These disclosure requirements are reflected in the Note 12, "Pension and Postretirement Benefits." ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes This pronouncement simplifies the accounting for income taxes by eliminating certain exceptions to the general principles in ASC 740, income taxes. It also improves consistency of application for other areas of the guidance by clarifying and amending existing guidance. We adopted the amendments of this pronouncement as of January 1, 2021 with no material impact to the Consolidated Financial Statements.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
Revenue Recognition (Tables)	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The table below reconciles revenue disaggregation by customer class to segment revenue as well as to revenues reflected on the Statements of Consolidated Income (Loss): Year Ended December 31, 2020 (in millions) Gas Distribution Operations Electric Operations Corporate and Other (2) Total Customer Revenues (1) Residential $ 2,075.0 $ 527.8 $ — $ 2,602.8 Commercial 670.5 480.3 — 1,150.8 Industrial 212.8 412.1 — 624.9 Off-system 41.0 — — 41.0 Miscellaneous 32.7 20.2 0.8 53.7 Total Customer Revenues $ 3,032.0 $ 1,440.4 $ 0.8 $ 4,473.2 Other Revenues 96.1 95.5 16.9 208.5 Total Operating Revenues $ 3,128.1 $ 1,535.9 $ 17.7 $ 4,681.7 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues. (2) Other revenues related to the Transition Services Agreement entered into in connection with the sale of the Massachusetts Business. Year Ended December 31, 2019 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Customer Revenues (1) Residential $ 2,309.0 $ 481.6 $ — $ 2,790.6 Commercial 771.3 486.6 — 1,257.9 Industrial 245.2 607.7 — 852.9 Off-system 77.7 — — 77.7 Miscellaneous 52.0 21.5 0.8 74.3 Total Customer Revenues $ 3,455.2 $ 1,597.4 $ 0.8 $ 5,053.4 Other Revenues 54.5 101.0 — 155.5 Total Operating Revenues $ 3,509.7 $ 1,698.4 $ 0.8 $ 5,208.9 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues. Year Ended December 31, 2018 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Customer Revenues (1) Residential $ 2,250.0 $ 494.7 $ — $ 2,744.7 Commercial 751.9 492.7 — 1,244.6 Industrial 228.0 613.6 — 841.6 Off-system 92.4 — — 92.4 Miscellaneous 49.7 17.4 0.7 67.8 Total Customer Revenues $ 3,372.0 $ 1,618.4 $ 0.7 $ 4,991.1 Other Revenues 34.4 89.0 — 123.4 Total Operating Revenues $ 3,406.4 $ 1,707.4 $ 0.7 $ 5,114.5 (1) Customer revenue amounts exclude intersegment revenues. See Note 24, "Segments of Business," for discussion of intersegment revenues.
Customer Accounts Receivable	The opening and closing balances of customer receivables for the years ended December 31, 2020 and 2019 are presented in the table below. We had no significant contract assets or liabilities during the period. Additionally, we have not incurred any significant costs to obtain or fulfill contracts. (in millions) Customer Accounts Receivable, Billed (less reserve) (1) Customer Accounts Receivable, Unbilled (less reserve) Balance as of December 31, 2019 $ 466.6 $ 346.6 Balance as of December 31, 2020 400.0 327.2 Decrease $ (66.6) $ (19.4) (1) Customer billed receivables decreased due to decreased natural gas costs and warmer weather in 2020 compared to 2019.
Financing Receivable, Allowance for Credit Loss	A rollforward of our allowance for credit losses for the year ended December 31, 2020 are presented in the table below: Year Ended December 31, 2020 (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Beginning balance (1) 9.1 3.1 0.8 13.0 Current period provisions 45.3 9.3 — 54.6 Write-offs charged against allowance (26.7) (3.0) — (29.7) Recoveries of amounts previously written off 14.1 0.3 — 14.4 Ending balance of the allowance for credit losses 41.8 9.7 0.8 52.3 (1) Total beginning balance differs from that presented in the Consolidated Balance Sheets as it excludes Columbia of Massachusetts. Columbia of Massachusetts' customer receivables and related allowance for credit losses were included in the sale of the Massachusetts Business that occurred on October 9, 2020.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
Variable Interest Entities (Tables)	Dec. 31, 2020
Variable Interest Entities [Abstract]
Variable Interest Entities Assets and Liabilities	At December 31, 2020, our consolidated balance sheet included the following assets and liabilities associated with Rosewater: (in millions) Net Property, Plant and Equipment $ 175.6 Current assets 1.7 Total assets (1) $ 177.3 Current liabilities $ 15.3 Asset retirement obligations 5.5 Other noncurrent liabilities 0.1 Total liabilities $ 20.9 (1) The assets of Rosewater represent assets of a consolidated VIE that can be used only to settle obligations of the consolidated VIE.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares	The computation of diluted average common shares is as follows: Year Ended December 31, (in thousands) 2020 2019 2018 Denominator Basic average common shares outstanding 384,347 374,650 356,491 Dilutive potential common shares: Shares contingently issuable under employee stock plans — 929 — Shares restricted under employee stock plans — 154 — Forward agreements — 253 — Diluted Average Common Shares 384,347 375,986 356,491

Property, Plant And Equipment (

Property, Plant And Equipment (Tables)	12 Months Ended
Property, Plant And Equipment (Tables)	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule Of Property, Plant And Equipment	Our property, plant and equipment on the Consolidated Balance Sheets are classified as follows: At December 31, (in millions) 2020 2019 Property, Plant and Equipment Gas Distribution Utility (1) $ 14,010.2 $ 14,989.7 Electric Utility (1) 6,478.0 8,902.3 Corporate 197.3 153.3 Construction Work in Process 572.6 457.3 Renewable Generation Assets (2) 175.7 — Non-Utility and Other (3) 2,746.1 39.3 Total Property, Plant and Equipment $ 24,179.9 $ 24,541.9 Accumulated Depreciation and Amortization Gas Distribution Utility (1) $ (3,292.9) $ (3,556.0) Electric Utility (1) (2,305.0) (3,973.8) Corporate (109.3) (79.5) Renewable Generation Assets (2) (0.1) — Non-Utility and Other (3) (1,853.1) (20.4) Total Accumulated Depreciation and Amortization $ (7,560.4) $ (7,629.7) Net Property, Plant and Equipment $ 16,619.5 $ 16,912.2 (1) NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment. (2) Our renewable generation assets are part of our electric segment and represent Non-Utility Property, owned and operated by Rosewater Wind Generation LLC, a joint venture between NIPSCO and unrelated tax equity partner, and depreciated straight-line over 30 years. Refer to Note 4, "Variable Interest Entities" for additional information. (3) Non-Utility and Other as of December 31, 2020 includes net book value of $903.8 million related to R.M. Schahfer Generating Station, which was reclassified from Electric Utility in the second quarter of 2020. Depreciation expense for the remaining net book value continues to be recorded at the composite depreciation rate approved by the IURC. See Note 20-E, "Other Matters," for additional information.
Schedule Of Depreciation Provisions For Utility Plant As A Percentage Of The Original Cost	The weighted average depreciation provisions for utility plant, as a percentage of the original cost, for the periods ended December 31, 2020, 2019 and 2018 were as follows: 2020 2019 2018 Electric Operations (1) 3.4 % 2.8 % 2.9 % Gas Distribution Operations 2.3 % 2.5 % 2.2 %

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
Goodwill and Other Intangible Assets (Tables)	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following presents our goodwill balance allocated by segment as of December 31, 2020 and 2019: (in millions) 2020 2019 Gas Distribution Operations $ 1,485.9 $ 1,485.9 Electric Operations — — Corporate and Other — — Total $ 1,485.9 $ 1,485.9

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
Asset Retirement Obligations (Tables)	Dec. 31, 2020
Asset Retirement Obligation [Abstract]
Changes In Liability For Asset Retirement Obligations	Changes in our liability for asset retirement obligations for the years 2020 and 2019 are presented in the table below: (in millions) 2020 2019 Beginning Balance $ 416.9 $ 352.0 Accretion recorded as a regulatory asset/liability 17.3 15.7 Additions 5.5 — Settlements (13.9) (5.4) Change in estimated cash flows 86.0 (1) 54.6 (2) Other (16.2) (3) — Ending Balance $ 495.6 $ 416.9 (1) The change in estimated cash flows for 2020 is primarily attributed to revisions to the estimated costs associated with refining the CCR compliance plan, changes in estimated costs for electric generating stations and the changes in estimated costs for retirement of gas mains. See Note 20-D. "Environmental Matters" for additional information on CCRs. (2) The change in estimated cash flows for 2019 is primarily attributed to changes in estimated costs and settlement timing for electric generating stations and the changes in estimated costs for retirement of gas mains. (3) Represents the Columbia of Massachusetts Asset Retirement Obligations that were included in the sale of the Massachusetts Business that occurred on October 9, 2020.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
Regulatory Matters (Tables)	Dec. 31, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	Regulatory assets were comprised of the following items: At December 31, (in millions) 2020 2019 Regulatory Assets Unrecognized pension and other postretirement benefit costs (see Note 12) $ 583.3 $ 739.1 Deferred pension and other postretirement benefit costs (see Note 12) 72.4 91.3 Environmental costs (see Note 20-D) 56.6 73.4 Regulatory effects of accounting for income taxes (see Note 1-N and Note 11) 194.5 234.0 Under-recovered gas and fuel costs (see Note 1-J) 8.0 3.9 Depreciation 192.6 210.7 Post-in-service carrying charges 228.6 219.8 Safety activity costs 146.0 118.6 DSM programs 37.8 50.1 Bailly Generating Station 204.7 221.8 Losses on Commodity Price Risk Programs (See Note 10) 54.7 76.4 Deferred Property Taxes 62.9 60.3 Other 88.4 140.2 Total Regulatory Assets $ 1,930.5 $ 2,239.6 Less: Current Portion 135.7 225.7 Total Noncurrent Regulatory Assets $ 1,794.8 $ 2,013.9
Regulatory Liabilities	Regulatory liabilities were comprised of the following items: At December 31, (in millions) 2020 2019 Regulatory Liabilities Over-recovered gas and fuel costs (see Note 1-J) $ 47.8 $ 42.6 Cost of removal (see Note 8) 775.2 1,047.5 Regulatory effects of accounting for income taxes (see Note 1-N and Note 11) 1,105.1 1,307.0 Deferred pension and other postretirement benefit costs (see Note 12) 69.5 64.7 Other 67.9 50.4 Total Regulatory Liabilities $ 2,065.5 $ 2,512.2 Less: Current Portion 161.3 160.2 Total Noncurrent Regulatory Liabilities $ 1,904.2 $ 2,352.0

Risk Management Activities (Tab

Risk Management Activities (Tables)	12 Months Ended
Risk Management Activities (Tables)	Dec. 31, 2020
Risk Management Activities [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	Risk management assets and liabilities on our derivatives are presented on the Consolidated Balance Sheets as shown below: December 31, (in millions) 2020 2019 Risk Management Assets - Current (1) Interest rate risk programs $ — $ — Commodity price risk programs 10.4 0.6 Total $ 10.4 $ 0.6 Risk Management Assets - Noncurrent (2) Interest rate risk programs $ — $ — Commodity price risk programs 2.8 3.8 Total $ 2.8 $ 3.8 Risk Management Liabilities - Current Interest rate risk programs $ 70.9 $ — Commodity price risk programs 7.3 12.6 Total $ 78.2 $ 12.6 Risk Management Liabilities - Noncurrent Interest rate risk programs $ 99.5 $ 76.2 Commodity price risk programs 45.1 57.8 Total $ 144.6 $ 134.0 (1) Presented in "Prepayments and other" on the Consolidated Balance Sheets. (2) Presented in "Deferred charges and other" on the Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule Of Components Of Income Tax Expense	The components of income tax expense (benefit) were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Income Taxes Current Federal $ 0.2 $ — $ — State 11.7 5.2 8.2 Total Current 11.9 5.2 8.2 Deferred Federal (0.4) 110.7 (209.4) State (27.4) 9.0 22.2 Total Deferred (27.8) 119.7 (187.2) Deferred Investment Credits (1.2) (1.4) (1.0) Income Taxes $ (17.1) $ 123.5 $ (180.0)
Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes	The following table represents a reconciliation of income tax expense at the statutory federal income tax rate to the actual income tax expense from continuing operations: Year Ended December 31, (in millions) 2020 2019 2018 Book income (loss) before income taxes $ (31.3) $ 506.6 $ (230.6) Tax expense (benefit) at statutory federal income tax rate (6.6) 21.0 % 106.5 21.0 % (48.4) 21.0 % Increases (reductions) in taxes resulting from: State income taxes, net of federal income tax benefit (11.7) 37.4 10.1 2.0 24.7 (10.7) Amortization of regulatory liabilities (38.4) 122.7 (29.4) (5.8) (29.3) 12.7 Goodwill impairment — — 43.0 8.5 — — Fines and penalties 11.8 (37.7) 11.5 2.3 0.2 (0.1) Charitable contribution carryover — — (2.5) (0.5) — — State regulatory proceedings — — (9.5) (1.9) (127.8) 55.4 Employee stock ownership plan dividends and other compensation (1.3) 4.2 (2.0) (0.4) (2.2) 1.0 Deferred taxes on TCJA regulatory liability divested 23.3 (74.5) — — — — Tax accrual adjustments 8.9 (28.4) — — — — Federal tax credits (2.5) 8.0 — — — — Other adjustments (0.6) 1.9 (4.2) (0.8) 2.8 (1.2) Income Taxes $ (17.1) 54.6 % $ 123.5 24.4 % $ (180.0) 78.1 %
Schedule Of Principal Components Of Net Deferred Tax Liability	Deferred income taxes result from temporary differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. The principal components of our net deferred tax liability were as follows: At December 31, (in millions) 2020 2019 Deferred tax liabilities Accelerated depreciation and other property differences $ 2,339.3 $ 2,516.9 Other regulatory assets 331.8 381.5 Total Deferred Tax Liabilities 2,671.1 2,898.4 Deferred tax assets Other regulatory liabilities and deferred investment tax credits (including TCJA) 287.8 336.1 Pension and other postretirement/postemployment benefits 118.1 152.1 Net operating loss carryforward and AMT credit carryforward 602.1 765.9 Environmental liabilities 22.6 25.4 Other accrued liabilities 41.5 35.3 Other, net 128.4 98.3 Total Deferred Tax Assets 1,200.5 1,413.1 Net Deferred Tax Liabilities $ 1,470.6 $ 1,485.3
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows: Reconciliation of Unrecognized Tax Benefits (in millions) 2020 2019 2018 Unrecognized Tax Benefits - Opening Balance $ 23.2 $ 1.2 $ 1.4 Gross decreases - tax positions in prior period (1.5) (0.6) (0.4) Gross increases - current period tax positions — 22.6 0.2 Unrecognized Tax Benefits - Ending Balance $ 21.7 $ 23.2 $ 1.2 Offset for net operating loss carryforwards (21.7) (22.6) — Balance - Less Net Operating Loss Carryforwards $ — $ 0.6 $ 1.2

Pension and Other Postretirem_2

Pension and Other Postretirement Benefits (Tables)	12 Months Ended
Pension and Other Postretirement Benefits (Tables)	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Allocation of Plan Assets	Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 12% 32% 0% 55% International Equities 6% 16% 0% 25% Fixed Income 59% 71% 20% 100% Real Estate 0% 7% 0% 0% Private Equity 0% 5% 0% 0% Short-Term Investments 0% 10% 0% 10% As of December 31, 2019, the asset mix and acceptable minimum and maximum ranges established by the policy for the pension and other postretirement benefit plans were as follows: Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 12% 32% 0% 55% International Equities 6% 16% 0% 25% Fixed Income 59% 71% 20% 100% Real Estate 0% 7% 0% 0% Private Equity 0% 5% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2020 and December 31, 2019: Defined Benefit December 31, Postretirement December 31, Asset Class (in millions) Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 446.3 21.0 % $ 108.8 38.0 % International Equities 230.1 10.9 % 48.2 16.8 % Fixed Income 1,291.2 61.0 % 122.0 42.6 % Real Estate 52.9 2.5 % — — Cash/Other 97.2 4.6 % 7.4 2.6 % Total $ 2,117.7 100.0 % $ 286.4 100.0 % Defined Benefit Pension Assets December 31, Postretirement Benefit Plan Assets December 31, Asset Class (in millions) Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 446.4 21.5 % $ 93.8 35.9 % International Equities 205.0 9.9 % 40.7 15.6 % Fixed Income 1,337.2 64.2 % 119.5 45.7 % Real Estate 53.9 2.6 % — — Cash/Other 38.4 1.8 % 7.4 2.8 % Total $ 2,080.9 100.0 % $ 261.4 100.0 %
Schedule Of Fair Value and Changes In The Fair Value Of The Plan Assets	Fair Value Measurements at December 31, 2020: (in millions) December 31, Quoted Prices in Active Markets for Significant Other Significant Pension plan assets: Cash $ 11.9 $ 11.9 $ — $ — Equity securities U.S. equities 2.4 2.4 — — Fixed income securities Government 243.4 — 243.4 — Corporate 692.6 — 692.6 — Mutual Funds U.S. multi-strategy 161.3 161.3 — — International equities 55.4 55.4 — — Fixed income 0.1 0.1 — — Private equity limited partnerships (3) U.S. multi-strategy (1) 10.9 — — — International multi-strategy (2) 6.6 — — — Distressed opportunities 0.3 — — — Real estate 52.9 — — — Commingled funds (3) Short-term money markets 78.8 — — — U.S. equities 279.7 — — — International equities 176.8 — — — Fixed income 337.6 — — — Pension plan assets subtotal 2,110.7 231.1 936.0 — Other postretirement benefit plan assets: Mutual funds U.S. multi-strategy 94.8 94.8 — — International equities 24.1 24.1 — — Fixed income 121.8 121.8 — — Commingled funds (3) Short-term money markets 7.6 — — — U.S. equities 14.0 — — — International equities 24.1 — — — Other postretirement benefit plan assets subtotal 286.4 240.7 — — Due to brokers, net (4) (1.6) — (1.6) — Accrued income/dividends 8.6 8.6 — — Total pension and other postretirement benefit plan assets $ 2,404.1 $ 480.4 $ 934.4 $ — (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2020: (in millions) Fair Value Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 86.4 Daily 1 day U.S. equities 293.7 Daily 1-5 days International equities 200.9 Monthly 10-30 days Fixed income 337.6 Daily 3 days Total $ 918.6 Fair Value Measurements at December 31, 2019: (in millions) December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Significant Pension plan assets: Cash $ 6.7 $ 6.7 $ — $ — Fixed income securities Government 319.6 — 319.6 — Corporate 651.8 — 651.8 — Mutual Funds U.S. multi-strategy 140.5 140.5 — — International equities 56.9 56.9 — — Private equity limited partnerships (3) U.S. multi-strategy (1) 14.0 — — — International multi-strategy (2) 8.5 — — — Distressed opportunities 0.5 — — — Real Estate 53.9 — — — Commingled funds (3) Short-term money markets 14.8 — — — U.S. equities 305.9 — — — International equities 148.1 — — — Fixed income 351.8 — — — Pension plan assets subtotal 2,073.0 204.1 971.4 — Other postretirement benefit plan assets: Mutual funds U.S. multi-strategy 81.7 81.7 — — International equities 20.6 20.6 — — Fixed income 119.2 119.2 — — Commingled funds (3) Short-term money markets 7.7 — — — U.S. equities 12.1 — — — International equities 20.1 — — — Other postretirement benefit plan assets subtotal 261.4 221.5 — — Due to brokers, net (4) (2.8) — (2.8) — Accrued income/dividends 10.7 10.7 — — Total pension and other postretirement benefit plan assets $ 2,342.3 $ 436.3 $ 968.6 $ — (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2019: Balance at January 1, 2019 Transfers out (Level 3) (1) Balance at December 31, 2019 Private equity limited partnerships U.S. multi-strategy 18.5 (18.5) — International multi-strategy 12.5 (12.5) — Distress opportunities 2.4 (2.4) — Real estate 52.7 (52.7) — Total $ 86.1 $ (86.1) $ — (1) Level 3 assets from 2018 were reclassified in the 2019 presentation and included within the fair value hierarchy table as of December 31, 2019 as "Not Classified" investments for which fair value is measured using net asset value per share, consistent with the definitions described above. The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2019: (in millions) Fair Value Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 22.5 Daily 1 day U.S. equities 318.0 Monthly 3 days International equities 168.2 Monthly 10-30 days Fixed income 351.8 Daily 3 days Total $ 860.5
Schedule Of Reconciliation Of The Plan Funded Status	The following table provides a reconciliation of the plans’ funded status and amounts reflected in our Consolidated Balance Sheets at December 31 based on a December 31 measurement date: Pension Benefits Other Postretirement Benefits (in millions) 2020 2019 2020 2019 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 2,130.5 $ 1,981.3 $ 576.5 $ 492.5 Service cost 32.0 29.2 6.6 5.1 Interest cost 51.6 72.3 15.4 19.2 Plan participants’ contributions — — 4.1 4.8 Plan amendments — — — 5.1 Actuarial loss (2) 140.1 204.3 24.8 88.8 Benefits paid (174.5) (156.6) (37.0) (39.5) Estimated benefits paid by incurred subsidy — — 0.4 0.5 Spinoff to Eversource (121.3) — — — Projected benefit obligation at end of year $ 2,058.4 $ 2,130.5 $ 590.8 $ 576.5 Change in plan assets Fair value of plan assets at beginning of year $ 2,080.9 $ 1,867.7 $ 261.4 $ 216.3 Actual return on plan assets 329.9 366.8 36.3 56.9 Employer contributions 2.9 2.9 21.6 23.0 Plan participants’ contributions — — 4.1 4.7 Benefits paid (174.6) (156.5) (37.0) (39.5) Spinoff to Eversource (121.4) — — — Fair value of plan assets at end of year $ 2,117.7 $ 2,080.9 $ 286.4 $ 261.4 Funded Status at end of year $ 59.3 $ (49.6) $ (304.4) $ (315.1) Amounts recognized in the statement of financial position consist of: Noncurrent assets 91.4 8.2 — — Current liabilities (2.9) (3.0) (0.9) (0.8) Noncurrent liabilities (29.2) (54.8) (303.5) (314.3) Net amount recognized at end of year (3) $ 59.3 $ (49.6) $ (304.4) $ (315.1) Amounts recognized in accumulated other comprehensive income or regulatory asset/liability (4) Unrecognized prior service credit $ 0.3 $ 3.0 $ (10.1) $ (10.7) Unrecognized actuarial loss 497.2 652.8 116.4 118.4 Net amount recognized at end of year $ 497.5 $ 655.8 $ 106.3 $ 107.7 (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in accumulated postretirement benefit obligation. (2) The pension actuarial loss was primarily driven by the decrease in the discount rate, offset by the change in mortality assumptions. The other postretirement benefits loss was also primarily driven by a decrease in discount rates, offset by favorable claims experienced and a change in the mortality assumptions. (3) We recognize our Consolidated Balance Sheets underfunded and overfunded status of our various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (3) We determined that for certain rate-regulated subsidiaries the future recovery of pension and other postretirement benefits costs is probable. These rate-regulated subsidiaries recorded regulatory assets and liabilities of $583.3 million and zero, respectively, as of December 31, 2020, and $739.1 million and $0.1 million, respectively, as of December 31, 2019 that would otherwise have been recorded to accumulated other comprehensive loss.
Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets	Information for pension plans with a projected benefit obligation in excess of plan assets: December 31, 2020 (1) 2019 Accumulated Benefit Obligation $ 32.1 $ 1,473.9 Funded Status Projected Benefit Obligation 32.1 1,492.9 Fair Value of Plan Assets — 1,435.1 Funded Status of Underfunded Pension Plans at End of Year $ (32.1) $ (57.8) (1)As of December 31, 2020, only our nonqualified plans were underfunded. These plans have no assets as they are not funded until benefits are paid. Information for pension plans with plan assets in excess of the projected benefit obligation: December 31, 2020 2019 Accumulated Benefit Obligation $ 2,004.7 $ 637.6 Funded Status Projected Benefit Obligation 2,026.3 637.6 Fair Value of Plan Assets 2,117.7 645.8 Funded Status of Overfunded Pension Plans at End of Year $ 91.4 $ 8.2
Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan	The following table provides the key assumptions that were used to calculate the pension and other postretirement benefits obligations for our various plans as of December 31: Pension Benefits Other Postretirement Benefits 2020 2019 2020 2019 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 2.38 % 3.12 % 2.49 % 3.21 % Rate of Compensation Increases 4.00 % 4.00 % — — Interest Crediting Rates 4.00 % 4.00 % — — Health Care Trend Rates Trend for Next Year — — 6.69 % 6.68 % Ultimate Trend — — 4.50 % 4.50 % Year Ultimate Trend Reached — — 2029 2028 The following table provides the key assumptions that were used to calculate the net periodic benefits cost for our various plans: Pension Benefits Other Postretirement 2020 2019 2018 2020 2019 2018 Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount rate - service cost 3.39 % 4.48 % 3.79 % 3.52 % 4.59 % 3.89 % Discount rate - interest cost 2.65 % 3.84 % 3.15 % 2.76 % 3.94 % 3.27 % Expected Long-Term Rate of Return on Plan Assets 5.70 % 6.10 % 7.00 % 5.67 % 5.83 % 5.80 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 % — — — Interest Crediting Rates 4.00 % 4.00 % 4.00 % — — —
Schedule Of Expected Payments To Participants In Pension Plan	The expected benefits are estimated based on the same assumptions used to measure our benefit obligation at the end of the year and include benefits attributable to the estimated future service of employees: (in millions) Pension Benefits Other Federal Year(s) 2021 $ 218.8 $ 38.4 $ 0.4 2022 154.5 37.8 0.4 2023 149.2 37.3 0.4 2024 145.9 37.0 0.4 2025 141.3 36.6 0.3 2026-2030 621.9 172.1 1.2
Components Of The Plans' Net Periodic Benefits Cost	The following table provides the components of the plans’ actuarially determined net periodic benefits cost for each of the three years ended December 31, 2020, 2019 and 2018: Pension Benefits Other Postretirement (in millions) 2020 2019 2018 2020 2019 2018 Components of Net Periodic Benefit Cost (1) Service cost $ 32.0 $ 29.2 $ 31.3 $ 6.6 $ 5.1 $ 5.0 Interest cost 51.6 72.3 67.1 15.4 19.2 17.6 Expected return on assets (111.6) (108.8) (142.3) (14.4) (13.1) (14.9) Amortization of prior service cost (credit) 0.7 0.2 (0.4) (2.1) (3.2) (4.0) Recognized actuarial loss 33.8 45.2 40.6 4.9 2.0 3.8 Settlement/curtailment loss 10.5 9.5 18.5 1.5 — — Total Net Periodic Benefits Cost $ 17.0 $ 47.6 $ 14.8 $ 11.9 $ 10.0 $ 7.5 (1) Service cost is presented in "Operation and maintenance" on the Statements of Consolidated Income (Loss). Non-service cost components are presented within "Other, net."
Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income	The following table provides other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory asset or liability: Pension Benefits Other Postretirement (in millions) 2020 2019 2020 2019 Other Changes in Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive Income or Regulatory Asset or Liability Net prior service cost $ — $ — $ — $ 5.1 Net actuarial loss (gain) (78.2) (53.8) 2.9 45.1 Settlements/curtailments (10.5) (9.5) (1.5) — Less: amortization of prior service cost (0.7) (0.2) 2.1 3.2 Less: amortization of net actuarial loss (33.8) (45.2) (4.9) (2.0) Less: gain attributable to spinoff to Eversource (33.1) — — — Less: prior service cost attributable to spinoff to Eversource (2.0) — — — Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability $ (158.3) $ (108.7) $ (1.4) $ 51.4 Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability $ (141.3) $ (61.1) $ 10.5 $ 61.4

Equity (Tables)

Equity (Tables)	12 Months Ended
Equity (Tables)	Dec. 31, 2020
Equity [Abstract]
Schedule Of Stock Offering Program	The following table summarizes our activity under the ATM program: Year Ending December 31, 2020 2019 2018 Number of shares issued 8,459,430 8,422,498 8,883,014 Average price per share $ 23.60 $ 27.75 $ 26.85 Proceeds, net of fees ( in millions) $ 196.5 $ 229.1 $ 232.5
Schedule of Stock by Class - Preferred	The following table summarizes preferred stock by outstanding series of shares: Year ended December 31, December 31, December 31, 2020 2019 2018 2020 2019 (in millions except shares and per share amounts) Liquidation Preference Per Share Shares Dividends Declared Per Share Outstanding 5.650% Series A $ 1,000.00 400,000 $ 56.50 $ 56.50 $ 28.88 $ 393.9 $ 393.9 6.500% Series B $ 25,000.00 20,000 $ 1,625.00 $ 1,674.65 $ — $ 486.1 $ 486.1

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
Share-Based Compensation (Tables)	Dec. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract]
Performance Award Details	The following table presents details of the performance awards described above. Award Year Service Conditions Lapse date Performance Period Award Conditions Shares outstanding at 12/31/2020 (shares) Grant Date Fair Value (in millions) 2020 02/28/23 01/01/2020- Non-GAAP Financial Measure 392,619 $ 11.7 Operational Measures 90,604 $ 2.6 2019 02/28/22 01/01/2019- Non-GAAP Financial Measure 384,680 $ 11.7 Operational Measures 88,769 $ 2.5 2018 02/26/21 01/01/2018- Non-GAAP Financial Measure 347,479 $ 9.2 Operational Measures (1) 80,185 $ 2.4 (1) Grant date fair value amount represents the service inception date fair value of these awards as they are not yet granted.
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	(shares) Restricted Stock Weighted Average Non-vested at December 31, 2019 302,606 23.49 Granted 235,100 25.77 Forfeited (38,220) 24.18 Vested (21,259) 24.68 Non-vested at December 31, 2020 478,227 24.51
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	(shares) Performance Weighted Average Grant Date Fair Value Per Unit ($) (1) Non-vested at December 31, 2019 1,503,251 22.74 Granted 528,729 27.01 Forfeited (118,716) 25.63 Vested (528,928) 28.30 Non-vested at December 31, 2020 1,384,336 25.09

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2020
Long-term Debt, Current and Noncurrent [Abstract]
Schedule of Long-Term Debt	Our long-term debt as of December 31, 2020 and 2019 is as follows: Long-term debt type Maturity as of December 31, 2020 Weighted average interest rate (%) Outstanding balance as of December 31, (in millions) 2020 2019 Senior notes: NiSource December 2021 4.45 % — 63.6 NiSource November 2022 2.65 % — 500.0 NiSource February 2023 3.85 % — 250.0 NiSource June 2023 3.65 % — 350.0 NiSource August 2025 0.95 % 1,250.0 — NiSource November 2025 5.89 % — 265.0 NiSource May 2027 3.49 % 1,000.0 1,000.0 NiSource December 2027 6.78 % 3.0 3.0 NiSource September 2029 2.95 % 750.0 750.0 NiSource May 2030 3.60 % 1,000.0 — NiSource February 2031 1.70 % 750.0 — NiSource December 2040 6.25 % 152.6 250.0 NiSource June 2041 5.95 % 347.4 400.0 NiSource February 2042 5.80 % 250.0 250.0 NiSource February 2043 5.25 % 500.0 500.0 NiSource February 2044 4.80 % 750.0 750.0 NiSource February 2045 5.65 % 500.0 500.0 NiSource May 2047 4.38 % 1,000.0 1,000.0 NiSource March 2048 3.95 % 750.0 750.0 Total senior notes $ 9,003.0 $ 7,581.6 Medium term notes: NiSource April 2022 to May 2027 7.99 % $ 49.0 $ 49.0 NIPSCO August 2022 to August 2027 7.61 % 68.0 68.0 Columbia of Massachusetts (1) December 2025 to February 2028 6.37 % 15.0 40.0 Total medium term notes $ 132.0 $ 157.0 Finance leases: NiSource Corporate Services April 2022 to January 2025 2.19 % 49.4 22.3 NIPSCO November 2028 1.79 % 16.0 — Columbia of Ohio October 2021 to March 2044 6.16 % 91.2 94.8 Columbia of Virginia July 2029 to November 2039 6.30 % 18.4 19.1 Columbia of Kentucky May 2027 3.79 % 0.3 0.3 Columbia of Pennsylvania August 2027 to May 2035 5.65 % 19.7 20.7 Columbia of Massachusetts N/A — % — 44.3 Total finance leases 195.0 201.5 Unamortized issuance costs and discounts $ (86.9) $ (70.5) Total Long-Term Debt $ 9,243.1 $ 7,869.6 (1) Rate increased from 6.30% in 2019 to 6.37% in 2020 in connection with debt redemptions described below.

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
Short-Term Borrowings (Tables)	Dec. 31, 2020
Short-term Debt [Abstract]
Schedule Of Short-Term Borrowings	Short-term borrowings were as follows: At December 31, (in millions) 2020 2019 Commercial Paper weighted-average interest rate of 0.27% and 2.03% at December 31, 2020 and 2019, respectively $ 503.0 $ 570.0 Accounts receivable securitization facility borrowings — 353.2 Term loan interest rate of 2.40% at December 31, 2019 — $ 850.0 Total Short-Term Borrowings $ 503.0 $ 1,773.2

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2020
Leases [Abstract]
Lease Cost	Income statement presentation for these costs (when ultimately recognized on the income statement) is also included: Year Ended December 31, (in millions) Income Statement Classification 2020 2019 Finance lease cost Amortization of right-of-use assets Depreciation and amortization $ 23.4 $ 15.5 Interest on lease liabilities Interest expense, net 11.1 11.3 Total finance lease cost 34.5 26.8 Operating lease cost Operation and maintenance 20.3 17.9 Short-term lease cost Operation and maintenance — 1.0 Total lease cost $ 54.8 $ 45.7
Right-of-Use Assets and Liabilities	Our right-of-use assets and liabilities are presented in the following lines on the Consolidated Balance Sheets: At December 31, (in millions) Balance Sheet Classification 2020 2019 Assets Finance leases Net Property, Plant and Equipment $ 176.8 $ 179.5 Operating leases Deferred charges and other 39.9 64.2 Total leased assets 216.7 243.7 Liabilities Current Finance leases Current portion of long-term debt 23.3 13.4 Operating leases Other accruals 10.3 13.2 Noncurrent Finance leases Long-term debt, excluding amounts due within one year 171.7 188.1 Operating leases Other noncurrent liabilities 29.9 51.6 Total lease liabilities $ 235.2 $ 266.3
Lease Information	Other pertinent information related to leases was as follows: Year Ended December 31, (in millions) 2020 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for finance leases $ 11.1 $ 11.3 Operating cash flows used for operating leases 20.2 17.9 Financing cash flows used for finance leases 18.4 10.6 Right-of-use assets obtained in exchange for lease obligations Finance leases 59.3 26.4 Operating leases $ 10.9 $ 13.4 December 31, 2020 December 31, 2019 Weighted-average remaining lease term (years) Finance leases 11.2 14.8 Operating leases 8.0 9.2 Weighted-average discount rate Finance leases 5.1 % 5.9 % Operating leases 4.0 % 4.3 %
Lease Maturity	Maturities of our lease liabilities as of December 31, 2020 were as follows: As of December 31, 2020, (in millions) Total Finance Leases Operating Leases 2021 $ 44.4 $ 32.7 $ 11.7 2022 37.4 32.2 5.2 2023 33.5 28.8 4.7 2024 25.3 20.8 4.5 2025 19.8 16.1 3.7 Thereafter 152.3 134.1 18.2 Total lease payments 312.7 264.7 48.0 Less: Imputed interest (77.5) (69.7) (7.8) Total 235.2 195.0 40.2 Reported as of December 31, 2020 Short-term lease liabilities 33.6 23.3 10.3 Long-term lease liabilities 201.6 171.7 29.9 Total lease liabilities $ 235.2 $ 195.0 $ 40.2

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
Fair Value (Tables)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present financial assets and liabilities measured and recorded at fair value on our Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2020 and December 31, 2019: Recurring Fair Value Measurements December 31, 2020 ( in millions ) Quoted Prices Significant Other Significant Balance as of December 31, 2020 Assets Risk management assets $ — $ 13.2 $ — $ 13.2 Available-for-sale securities — 170.9 — 170.9 Total $ — $ 184.1 $ — $ 184.1 Liabilities Risk management liabilities $ — $ 222.8 $ — $ 222.8 Total $ — $ 222.8 $ — $ 222.8 Recurring Fair Value Measurements December 31, 2019 ( in millions ) Quoted Prices Significant Other Significant Balance as of December 31, 2019 Assets Risk management assets $ — $ 4.4 $ — $ 4.4 Available-for-sale securities — 154.2 — 154.2 Total $ — $ 158.6 $ — $ 158.6 Liabilities Risk management liabilities $ — $ 146.6 $ — $ 146.6 Total $ — $ 146.6 $ — $ 146.6
Available-For-Sale Debt Securities	at December 31, 2020 and 2019 were: December 31, 2020 (in millions) Amortized Gross Gross Unrealized Losses (1) Allowance for Credit Losses Fair Value Available-for-sale debt securities U.S. Treasury debt securities $ 33.7 $ 0.3 $ — $ — $ 34.0 Corporate/Other debt securities 130.2 7.7 (0.5) (0.5) 136.9 Total $ 163.9 $ 8.0 $ (0.5) $ (0.5) $ 170.9 December 31, 2019 (in millions) Amortized Gross Gross Unrealized Losses (2) Allowance for Credit Losses Fair Value Available-for-sale debt securities U.S. Treasury debt securities $ 31.4 $ 0.1 $ (0.1) $ — $ 31.4 Corporate/Other debt securities 118.7 4.2 (0.1) — 122.8 Total $ 150.1 $ 4.3 $ (0.2) $ — $ 154.2
Carrying Amount And Estimated Fair Values Of Financial Instruments	The carrying amount and estimated fair values of these financial instruments were as follows: At December 31, (in millions) Carrying Amount 2020 Estimated Fair Value 2020 Carrying Amount 2019 Estimated Fair Value 2019 Long-term debt (including current portion) $ 9,243.1 $ 11,034.2 $ 7,869.6 $ 8,764.4

Transfers Of Financial Assets (

Transfers Of Financial Assets (Tables)	12 Months Ended
Transfers Of Financial Assets (Tables)	Dec. 31, 2020
Transfers and Servicing [Abstract]
Schedule of Assets and Associated Liabilities Accounted for as Secured Borrowings	The following table reflects the gross receivables balance and net receivables transferred as well as short-term borrowings related to the securitization transactions as of December 31, 2020 and 2019: At December 31, (in millions) 2020 2019 Gross receivables $ 607.7 $ 569.1 Less: receivables not transferred 607.7 215.9 Net receivables transferred $ — $ 353.2 Short-term debt due to asset securitization $ — $ 353.2

Other Commitments And Conting_2

Other Commitments And Contingencies (Tables)	12 Months Ended
Other Commitments And Contingencies (Tables)	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity	Contractual Obligations. We have certain contractual obligations requiring payments at specified periods. The obligations include long-term debt, lease obligations, energy commodity contracts and obligations for various services including pipeline capacity and outsourcing of IT services. The total contractual obligations in existence at December 31, 2020 and their maturities were: (in millions) Total 2021 2022 2023 2024 2025 After Long-term debt (1) $ 9,135.0 $ — $ 30.0 $ — $ — $ 1,260.0 $ 7,845.0 Interest payments on long-term debt 6,046.3 336.3 335.7 334.1 334.1 334.1 4,372.0 Finance leases (2) 264.7 32.7 32.2 28.8 20.8 16.1 134.1 Operating leases (3) 48.0 11.7 5.2 4.7 4.5 3.7 18.2 Energy commodity contracts 42.1 42.1 — — — — — Service obligations: Pipeline service obligations (4) 1,495.6 468.7 422.5 256.0 150.5 56.2 141.7 IT service obligations 240.3 74.9 74.0 38.1 30.5 22.8 — Other service obligations (5) 12.6 12.6 — — — — — Other liabilities (6) 116.9 26.0 0.8 90.1 — — — Total contractual obligations $ 17,401.5 $ 1,005.0 $ 900.4 $ 751.8 $ 540.4 $ 1,692.9 $ 12,511.0 (1) Long-term debt balance excludes unamortized issuance costs and discounts of $86.9 million. (2) Finance lease payments shown above are inclusive of interest totaling $69.7 million. (3) Operating lease payments shown above are inclusive of interest totaling $7.8 million. Operating lease balances do not include obligations for possible fleet vehicle lease renewals beyond the initial lease term. While we have the ability to renew these leases beyond the initial term, we are not reasonably certain (as that term is defined in ASC 842) to do so as they are renewed month-to-month after the first year. If we were to continue the fleet vehicle leases outstanding at December 31, 2020, payments would be $30.0 million in 2021, $27.7 million in 2022, $24.9 million in 2023, $22.0 million in 2024, $19.0 million in 2025 and $21.5 million thereafter. (4) In February 2021, the demand rate increased for our pipeline service obligations, resulting in a total increase of $638.6 million in addition to our future pipeline service obligations shown above. (5) On February 9, 2021, a rail transportation contract for the transportation of coal was fully executed between NIPSCO and a counterparty, replacing the prior agreement. The minimum coal tonnage shipment commitment for 2021 was eliminated under the new agreement, reducing our contractual obligation for 2021 by $12.1 million. (6) Other liabilities shown above are inclusive of the Rosewater Developer payment due in 2023.
Expenses Incurred and Insurance Recoveries	The following table summarizes expenses incurred and insurance recoveries recorded since the Greater Lawrence Incident. This activity is presented within "Operation and maintenance" and "Other, net" in our Statements of Consolidated Income (Loss). Total Costs Incurred through Year Ended (in millions) December 31, 2019 December 31, 2020 Incident to Date Third-party claims and government fines, penalties and settlements $ 1,041 $ (5) $ 1,036 Other incident-related costs 420 22 442 Total 1,461 17 1,478 Insurance recoveries recorded (800) — (800) Total costs incurred $ 661 $ 17 $ 678
Estimated Incident Expenses	The following table summarizes the total estimated incident-related expenses. (in millions) Current Total Estimated Amount Third-party claims and government fines, penalties and settlements $1,036 - $1,050 Other incident-related costs $445 - $450
Schedule of Restructuring Reserve by Type of Cost	A rollforward of the voluntary separation program accrual for the year ended December 31, 2020 is presented below: (in millions) Balance as of January 1, 2020 Changes Attributable to Costs Incurred (1) Costs Paid Adjustments Balance as of December 31, 2020 (2) Voluntary Separation Program $ — 33.5 $ (21.2) (1.2) $ 11.1 (1) This activity is presented within "Operation and maintenance" in our Statements of Consolidated Income (Loss).

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
Accumulated Other Comprehensive Loss (Tables)	Dec. 31, 2020
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table displays the activity of Accumulated Other Comprehensive Loss, net of tax: (in millions) Gains and Losses on Securities (1) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Balance as of January 1, 2018 $ 0.2 $ (29.4) $ (14.2) $ (43.4) Other comprehensive income (loss) before reclassifications (3.0) 55.8 (4.4) 48.4 Amounts reclassified from accumulated other comprehensive loss 0.4 (33.1) — (32.7) Net current-period other comprehensive income (loss) (2.6) 22.7 (4.4) 15.7 Reclassification due to adoption of ASU 2018-02 — (6.3) (3.2) (9.5) Balance as of December 31, 2018 $ (2.4) $ (13.0) $ (21.8) $ (37.2) Other comprehensive income (loss) before reclassifications 6.1 (64.3) 2.3 (55.9) Amounts reclassified from accumulated other comprehensive loss (0.4) 0.1 0.8 0.5 Net current-period other comprehensive income (loss) 5.7 (64.2) 3.1 (55.4) Balance as of December 31, 2019 $ 3.3 $ (77.2) $ (18.7) $ (92.6) Other comprehensive income (loss) before reclassifications 3.3 (70.8) 2.9 (64.6) Amounts reclassified from accumulated other comprehensive loss (0.6) 0.1 1.0 0.5 Net current-period other comprehensive income (loss) 2.7 (70.7) 3.9 (64.1) Balance as of December 31, 2020 $ 6.0 $ (147.9) $ (14.8) $ (156.7) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Tables)

Other, Net (Tables)	12 Months Ended
Other, Net (Tables)	Dec. 31, 2020
Other Nonoperating Income (Expense) [Abstract]
Schedule Of Other, Net	Year Ended December 31, (in millions) 2020 2019 2018 Interest income $ 5.5 $ 7.7 $ 6.6 AFUDC equity 9.9 8.0 14.2 Charitable contributions (1) (1.5) (5.1) (45.3) Pension and other postretirement non-service cost (2) 9.3 (16.5) 18.0 Sale of emission reduction credits 4.6 — — Interest rate swap settlement gain (3) — — 46.2 Miscellaneous 4.3 0.7 3.8 Total Other, net $ 32.1 $ (5.2) $ 43.5 (1) 2018 charitable contributions include $20.7 million related to the Greater Lawrence Incident and $20.0 million of discretionary contributions made to the NiSource Charitable Foundation. See Note 20, "Other Commitments and Contingencies" for additional information on the Greater Lawrence Incident. (2) See Note 12, "Pension and Other Postretirement Benefits" for additional information. (3) See Note 10, "Risk Management Activities" for additional information.

Interest Expense, Net (Tables)

Interest Expense, Net (Tables)	12 Months Ended
Interest Expense, Net (Tables)	Dec. 31, 2020
Interest Expense [Abstract]
Schedule Of Interest Expense, Net	Year Ended December 31, (in millions) 2020 2019 2018 Interest on long-term debt $ 354.2 $ 327.7 $ 342.2 Interest on short-term borrowings 14.7 50.8 31.8 Debt discount/cost amortization 9.1 8.3 7.7 Accounts receivable securitization fees 2.6 2.6 2.6 Allowance for borrowed funds used and interest capitalized during construction (7.0) (7.5) (9.1) Debt-based post-in-service carrying charges (14.6) (18.7) (35.0) Other 11.7 15.7 13.1 Total Interest Expense, net $ 370.7 $ 378.9 $ 353.3

Segments Of Business (Tables)

Segments Of Business (Tables)	12 Months Ended
Segments Of Business (Tables)	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule Of Operating Income Derived From Revenues And Expenses By Segment	Year Ended December 31, (in millions) 2020 2019 2018 Operating Revenues Gas Distribution Operations Unaffiliated $ 3,128.1 $ 3,509.7 $ 3,406.4 Intersegment 12.1 13.1 13.1 Total 3,140.2 3,522.8 3,419.5 Electric Operations Unaffiliated 1,535.9 1,698.4 1,707.4 Intersegment 0.7 0.8 0.8 Total 1,536.6 1,699.2 1,708.2 Corporate and Other Unaffiliated 17.7 0.8 0.7 Intersegment 449.8 468.1 517.6 Total 467.5 468.9 518.3 Eliminations (462.6) (482.0) (531.5) Consolidated Operating Revenues $ 4,681.7 $ 5,208.9 $ 5,114.5 Year Ended December 31, (in millions) 2020 2019 2018 Operating Income (Loss) Gas Distribution Operations (1) $ 199.1 $ 675.4 $ (254.1) Electric Operations 348.8 406.8 386.1 Corporate and Other (2) 2.9 (191.5) (7.3) Consolidated Operating Income $ 550.8 $ 890.7 $ 124.7 Depreciation and Amortization Gas Distribution Operations $ 363.1 $ 403.2 $ 301.0 Electric Operations 321.3 277.3 262.9 Corporate and Other 41.5 36.9 35.7 Consolidated Depreciation and Amortization $ 725.9 $ 717.4 $ 599.6 Assets Gas Distribution Operations $ 13,433.0 $ 14,224.5 $ 13,527.0 Electric Operations 6,443.1 6,027.6 5,735.2 Corporate and Other 2,164.4 2,407.7 2,541.8 Consolidated Assets $ 22,040.5 $ 22,659.8 $ 21,804.0 Capital Expenditures (3) Gas Distribution Operations $ 1,266.9 $ 1,380.3 $ 1,315.3 Electric Operations 422.8 468.9 499.3 Corporate and Other 31.1 18.6 — Consolidated Capital Expenditures $ 1,720.8 $ 1,867.8 $ 1,814.6 (1) In 2020, Gas Distribution Operations reflects the loss of $412.4 million on the sale of the Massachusetts Business. For additional information, see Note 1, "Nature of Operations and Summary of Significant Accounting Policies". (2) In 2019, Corporate and Other reflects an impairment charge of $204.8 million for goodwill related to Columbia of Massachusetts. For additional information, see Note 7, "Goodwill and Other Intangible Assets." (3) Amounts differ from those presented on the Statements of Consolidated Cash Flows primarily due to the inclusion of capital expenditures in current liabilities, the capitalized portion of the Corporate Incentive Plan payout, and AFUDC Equity.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
Quarterly Financial Data (Tables)	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Data	(in millions, except per share data) First Quarter (1) Second Quarter (2) Third Quarter (3) Fourth Quarter (4) 2020 Operating Revenues $ 1,605.5 $ 962.7 $ 902.5 $ 1,211.0 Operating Income 148.2 91.7 92.8 218.1 Net Income (Loss) 75.6 (4.7) (172.9) 87.8 Net income attributable to noncontrolling interest — — — 3.4 Net Income (Loss) attributable to NiSource 75.6 (4.7) (172.9) 84.4 Preferred Dividends (13.8) (13.8) (13.8) (13.7) Net Income (Loss) Available to Common Shareholders 61.8 (18.5) (186.7) 70.7 Earnings (Loss) Per Share Basic Earnings (Loss) Per Share $ 0.16 $ (0.05) $ (0.49) $ 0.18 Diluted Earnings (Loss) Per Share $ 0.16 $ (0.05) $ (0.49) $ 0.18 2019 Operating Revenues $ 1,869.8 $ 1,010.4 $ 931.5 $ 1,397.2 Operating Income (Loss) 374.2 463.5 91.0 (38.0) Net Income (Loss) 218.9 296.9 6.6 (139.3) Preferred Dividends (13.8) (13.8) (13.8) (13.7) Net Income (Loss) Available to Common Shareholders 205.1 283.1 (7.2) (153.0) Earnings (Loss) Per Share Basic Earnings (Loss) Per Share $ 0.55 $ 0.76 $ (0.02) $ (0.41) Diluted Earnings (Loss) Per Share $ 0.55 $ 0.75 $ (0.02) $ (0.41) (1) Net income for the first quarter of 2020 was impacted by $280.2 million loss on sale of the Massachusetts Business. Net income for the first quarter of 2019 was impacted by $108.0 million in insurance recoveries (pretax) related to the Greater Lawrence Incident. See Note 1, "Company Structure and Principles of Consolidation" and Note 20-E, "Other Matters" for additional information. (2) Net income for the second quarter of 2020 was impacted by an additional $84.4 million loss on sale of the Massachusetts Business. Net income for the second quarter of 2019 was impacted by $297.0 million in insurance recoveries (pretax) related to the Greater Lawrence Incident. See Note 1, "Company Structure and Principles of Consolidation" and Note 20-E, "Other Matters" for additional information. (3) Net loss for the third quarter of 2020 was impacted by $243.4 million loss on early extinguishments of long-term debt. See Note 15, "Long-Term Debt" for additional information.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
Supplemental Cash Flow Information (Tables)	Dec. 31, 2020
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	The following table provides additional information regarding our Consolidated Statements of Cash Flows for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, (in millions) 2020 2019 2018 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities $ 170.4 $ 223.6 $ 152.0 Assets acquired under a finance lease 59.3 26.4 54.6 Assets acquired under an operating lease 10.9 13.4 — Reclassification of other property to regulatory assets (1) — — 245.3 Assets recorded for asset retirement obligations (2) 91.5 54.6 78.1 Obligation to developer at formation of joint venture (3) 69.7 — — Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 349.0 $ 349.7 $ 354.2 Cash paid for income taxes, net of refunds (4) (1.0) 10.8 3.3 (1) See Note 9 "Regulatory Matters" for additional information. (2) See Note 8 "Asset Retirement Obligations" for additional information. (3) Represents investing non-cash activity. See Note 4 "Variable Interest Entities" for additional information. (4) Amount of refunds in 2020 was greater than the amount of tax payments due to overpayments in 2019.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts (Tables)	12 Months Ended
Valuation and Qualifying Accounts (Tables)	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	NISOURCE INC. SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS Twelve months ended December 31, 2020 Additions ($ in millions) Balance Jan. 1, 2020 Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Dec. 31, 2020 Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 19.2 $ 31.6 $ 33.0 $ 31.5 $ 52.3 Reserve for other investments 3.0 — — 3.0 — Twelve months ended December 31, 2019 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 21.1 $ 21.6 $ 41.3 $ 64.8 $ 19.2 Reserve for other investments 3.0 — — — 3.0 Twelve months ended December 31, 2018 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 18.3 $ 20.2 $ 43.7 $ 61.1 $ 21.1 Reserve for other investments 3.0 — — — 3.0 (1) Charged to Other Accounts reflects the deferral of bad debt expense to a regulatory asset.

Nature of Operations And Summ_3

Nature of Operations And Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Oct. 09, 2020USD ($)	Feb. 26, 2020USD ($)
Basis Of Accounting Presentation [Line Items]
Number of customers			3,700,000
Net Proceeds from Sale						$ 1,113
Purchase Price							$ 1,100
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down			$ 412.4
Unbilled revenue, less reserves			338.3	$ 350.5
Other than Temporary Impairment Losses, Investments			$ 0	$ 0	$ 0
Pre-tax rate for allowance for funds used during construction			2.60%	3.00%	3.50%
Inventory valued using LIFO			$ 42.3	$ 47.2
Excess of replacement over LIFO value			(19.6)	(25.5)
Inventory valued using the weighted average cost methodology			148.8	203.7
Massachusetts Business [Domain]
Basis Of Accounting Presentation [Line Items]
Disposal Group, Including Discontinued Operation, Operating Income (Loss)			(422.3)	$ 36.8	$ (835.6)
Columbia Of Massachusetts
Basis Of Accounting Presentation [Line Items]
Settlement Agreement Payment in Lieu of Penalties			$ 56
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down	$ 84.4	$ 280.2

Revenue Recognition (Narrative)

Revenue Recognition (Narrative) (Details)	12 Months Ended
Revenue Recognition (Narrative) (Details)	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Service Area By County	20

Revenue Recognition (Disaggrega

Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Customer revenues	$ 4,473.2	$ 5,053.4	$ 4,991.1
Other revenues	208.5	155.5	123.4
Total Operating Revenues	4,681.7	5,208.9	5,114.5
Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	3,032	3,455.2	3,372
Other revenues	96.1	54.5	34.4
Total Operating Revenues	3,128.1	3,509.7	3,406.4
Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	1,440.4	1,597.4	1,618.4
Other revenues	95.5	101	89
Total Operating Revenues	1,535.9	1,698.4	1,707.4
Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	0.8	0.8	0.7
Other revenues	16.9	0	0
Total Operating Revenues	17.7	0.8	0.7
Residential
Disaggregation of Revenue [Line Items]
Customer revenues	2,602.8	2,790.6	2,744.7
Residential \| Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	2,075	2,309	2,250
Residential \| Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	527.8	481.6	494.7
Residential \| Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	0	0	0
Commercial
Disaggregation of Revenue [Line Items]
Customer revenues	1,150.8	1,257.9	1,244.6
Commercial \| Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	670.5	771.3	751.9
Commercial \| Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	480.3	486.6	492.7
Commercial \| Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	0	0	0
Industrial
Disaggregation of Revenue [Line Items]
Customer revenues	624.9	852.9	841.6
Industrial \| Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	212.8	245.2	228
Industrial \| Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	412.1	607.7	613.6
Industrial \| Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	0	0	0
Off-system
Disaggregation of Revenue [Line Items]
Customer revenues	41	77.7	92.4
Off-system \| Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	41	77.7	92.4
Off-system \| Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	0	0	0
Off-system \| Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	0	0	0
Miscellaneous
Disaggregation of Revenue [Line Items]
Customer revenues	53.7	74.3	67.8
Miscellaneous \| Gas Distribution Operations
Disaggregation of Revenue [Line Items]
Customer revenues	32.7	52	49.7
Miscellaneous \| Electric Operations
Disaggregation of Revenue [Line Items]
Customer revenues	20.2	21.5	17.4
Miscellaneous \| Corporate and Other
Disaggregation of Revenue [Line Items]
Customer revenues	$ 0.8	$ 0.8	$ 0.7

Revenue Recognition (Customer A

Revenue Recognition (Customer Accounts Receivable) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue Recognition [Abstract]
Customer Accounts Receivable, Billed (Less Reserve)	$ 400	$ 466.6
Customer Accounts Receivable, Unbilled (Less Reserve)	327.2	$ 346.6
Increase (Decrease) in Customer Accounts Receivable, Billed (Less Reserve)	(66.6)
Increase (Decrease) in Customer Accounts Receivable, Unbilled (Less Reserve)	$ (19.4)

Revenue Recognition (Allowance

Revenue Recognition (Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	$ 52.3	$ 13
Current period provisions	54.6
Write-offs charged against allowance	(29.7)
Recoveries of amounts previously written off	14.4
Gas Distribution Operations
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	41.8	9.1
Current period provisions	45.3
Write-offs charged against allowance	(26.7)
Recoveries of amounts previously written off	14.1
Electric Operations
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	9.7	3.1
Current period provisions	9.3
Write-offs charged against allowance	(3)
Recoveries of amounts previously written off	0.3
Corporate and Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	0.8	$ 0.8
Current period provisions	0
Write-offs charged against allowance	0
Recoveries of amounts previously written off	$ 0

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details)	3 Months Ended				12 Months Ended
Variable Interest Entities (Narrative) (Details)	Dec. 31, 2020USD ($)RateMW	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)RateMW	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Variable Interest Entity [Line Items]
Nameplate Capacity \| MW	102				102
Wind Power Purchase Agreement, Purchase Percentage \| Rate	100.00%				100.00%
Total Equity Membership Interest	100.00%				100.00%
Obligation to the Developer	$ 69,700,000				$ 69,700,000	$ 0	$ 0
Payment to renewable generation asset developer					85,300,000	0	0
Total Contributions	170,100,000				170,100,000
VIE Net Assets	156,400,000				156,400,000
Noncontrolling interest in consolidated subsidiaries	85,600,000				85,600,000	0
Net Income (Loss) Attributable to Noncontrolling Interest	3,400,000	$ 0	$ 0	$ 0	3,400,000	$ 0	$ 0
Expected Future Obligation to the Developer	6,000,000				$ 6,000,000
NIPSCO
Variable Interest Entity [Line Items]
Cash Contribution	700,000
Future Cash Contribution	$ 100,000
Rosewater
Variable Interest Entity [Line Items]
Wind Power Purchase Agreement, Purchase Percentage \| Rate	100.00%				100.00%
Tax Equity Partner
Variable Interest Entity [Line Items]
Cash Contribution	$ 86,100,000
Future Cash Contribution	$ 7,500,000

Variable Interest Entities (Sch

Variable Interest Entities (Schedule of VIE Assets and Liabilities) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
VIE Assets and Liabilities [Abstract]
Net Property, Plant and Equipment		$ 16,619.5	$ 16,912.2
Current assets	[1]	1,659.4	1,853.9
Total Assets		22,040.5	22,659.8	$ 21,804
Current liabilities		2,279.4	3,745.8
Asset retirement obligations		477.1	416.9
Other noncurrent liabilities		286.1	$ 228.2
Rosewater
VIE Assets and Liabilities [Abstract]
Net Property, Plant and Equipment		175.6
Current assets		1.7
Total Assets		177.3
Current liabilities		15.3
Asset retirement obligations		5.5
Other noncurrent liabilities		0.1
Total liabilities		$ 20.9

[1]	(1) Includes $175.6 million of net property, plant and equipment assets and $1.7 million of current assets of a consolidated VIE that may be used only to settle obligations of the consolidated VIE. Refer to Note 4 "Variable Interest Entity" for additional information.

Earnings Per Share (Details)

Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
Earnings Per Share (Details) - shares shares in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Basic Average Common Shares Outstanding	384,347	374,650	356,491
Shares contingently issuable under employee stock plans	0	929	0
Shares restricted under employee stock plans	0	154	0
Forward agreements	0	253	0
Diluted Average Common Shares	384,347	375,986	356,491

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation	$ 655.6	$ 612.2	$ 503.4
Capitalized Computer Software, Amortization	56.7	55.5	54.1
Capitalized Computer Software, Gross	136.4	169.6
Capitalized Cloud Computing, Amortization	3.4	1.6	$ 0.1
Capitalized Cloud Computing, Gross	$ 12.7	$ 14.2

Property, Plant And Equipment_3

Property, Plant And Equipment (Schedule Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	$ 24,179.9	$ 24,541.9
Accumulated Depreciation and Amortization	(7,560.4)	(7,629.7)
Net Property, Plant and Equipment	16,619.5	16,912.2
Plant and Equipment Associated with Schahfer Generating Station Retirement	903.8
Gas Distribution Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	14,010.2	14,989.7
Accumulated Depreciation and Amortization	(3,292.9)	(3,556)
Electric Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	6,478	8,902.3
Accumulated Depreciation and Amortization	(2,305)	(3,973.8)
Common Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	197.3	153.3
Accumulated Depreciation and Amortization	(109.3)	(79.5)
Construction Work In Process
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	572.6	457.3
Renewable Generation Assets
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	175.7	0
Accumulated Depreciation and Amortization	(0.1)	0
Non-Utility And Other
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	2,746.1	39.3
Accumulated Depreciation and Amortization	$ (1,853.1)	$ (20.4)

Property, Plant And Equipment P

Property, Plant And Equipment Property, Plant and Equipment (Schedule of Depreciation Provisions For Utility Plant as a Percentage of the Original Cost) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Electric Operations
Property, Plant and Equipment [Line Items]
Depreciation Provisions For Utility Plant Percentage	3.40%	2.80%	2.90%
Gas Distribution Operations
Property, Plant and Equipment [Line Items]
Depreciation Provisions For Utility Plant Percentage	2.30%	2.50%	2.20%

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 1,485.9	$ 1,485.9	$ 1,485.9
Intangible Assets, Net (Excluding Goodwill)	0	0	0
Amortization of Intangible Assets		0	11	$ 11
Intangible Assets, Net (Including Goodwill)	0		0
Gas Distribution Operations
Goodwill And Other Intangible Assets [Line Items]
Goodwill	1,485.9	1,485.9	1,485.9
Electric Operations
Goodwill And Other Intangible Assets [Line Items]
Goodwill	0	0	0
Corporate and Other
Goodwill And Other Intangible Assets [Line Items]
Goodwill	0	$ 0	0
Columbia Of Massachusetts
Goodwill And Other Intangible Assets [Line Items]
Goodwill	0		$ 0
Goodwill, Impairment Loss	204.8
Impairment of Intangible Assets, Finite-lived	$ 209.7

Asset Retirement Obligations (C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Beginning Balance	$ 416.9
Accretion recorded as a regulatory asset	17.3	$ 15.7
Additions	5.5	0
Settlements	(13.9)	(5.4)
Change in estimated cash flows	86	54.6
Other	(16.2)	0
Asset Retirement Obligation	495.6	416.9	$ 352
Ending Balance	$ 477.1	$ 416.9

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Regulatory Matters [Line Items]
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	$ 1,260.6	$ 1,524.3
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	41 years
Columbia Of Ohio
Regulatory Matters [Line Items]
COVID-19 related costs regulatory asset	$ 2
NIPSCO
Regulatory Matters [Line Items]
COVID-19 related costs regulatory asset	9.2
Columbia Of Maryland
Regulatory Matters [Line Items]
COVID-19 related costs regulatory asset	0.7
Columbia Of Pennsylvania
Regulatory Matters [Line Items]
COVID-19 related costs regulatory asset	$ 5.4

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Total Assets	$ 1,930.5	$ 2,239.6
Regulatory Assets, Current	135.7	225.7
Regulatory Assets, Noncurrent	1,794.8	2,013.9
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Regulatory Assets [Line Items]
Total Assets	583.3	739.1
Other Postretirement Costs
Regulatory Assets [Line Items]
Total Assets	72.4	91.3
Environmental Costs
Regulatory Assets [Line Items]
Total Assets	56.6	73.4
Regulatory Effects Of Accounting For Income Taxes
Regulatory Assets [Line Items]
Total Assets	194.5	234
Underrecovered Gas And Fuel Costs
Regulatory Assets [Line Items]
Total Assets	8	3.9
Depreciation
Regulatory Assets [Line Items]
Total Assets	192.6	210.7
Post-In Service Carrying Charges
Regulatory Assets [Line Items]
Total Assets	228.6	219.8
Safety Activity Costs
Regulatory Assets [Line Items]
Total Assets	146	118.6
DSM Program
Regulatory Assets [Line Items]
Total Assets	37.8	50.1
Bailly Generating Station [Member]
Regulatory Assets [Line Items]
Total Assets	204.7	221.8
Deferred Derivative Gain (Loss)
Regulatory Assets [Line Items]
Total Assets	54.7	76.4
Deferred Property Taxes
Regulatory Assets [Line Items]
Total Assets	62.9	60.3
Other Assets
Regulatory Assets [Line Items]
Total Assets	$ 88.4	$ 140.2

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 2,065.5	$ 2,512.2
Regulatory Liability, Current	161.3	160.2
Regulatory Liability, Noncurrent	1,904.2	2,352
Overrecovered Gas And Fuel Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	47.8	42.6
Cost Of Removal
Regulatory Liabilities [Line Items]
Regulatory Liabilities	775.2	1,047.5
Regulatory Effects Of Accounting For Income Taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,105.1	1,307
Other Postretirement Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	69.5	64.7
Other Liabilities
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 67.9	$ 50.4

Risk Management Activities (Nar

Risk Management Activities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Limit of GCA Volumes	20.00%
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ 0	$ 0	$ 0
Minimum
Derivative [Line Items]
Commodity Contract Length	5 years
Maximum
Derivative [Line Items]
Commodity Contract Length	10 years
Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount	$ 500		750
Interest Rate Swap Settled
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0		$ 46.2

Risk Management Activities (Sch

Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 13.2	$ 4.4
Derivative Liability	222.8	146.6
Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset	10.4	0.6
Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset	2.8	3.8
Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability	78.2	12.6
Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability	144.6	134
Interest rate risk programs \| Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset	0	0
Interest rate risk programs \| Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset	0	0
Interest rate risk programs \| Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability	70.9	0
Interest rate risk programs \| Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability	99.5	76.2
Commodity price risk programs \| Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset	10.4	0.6
Commodity price risk programs \| Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset	2.8	3.8
Commodity price risk programs \| Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability	7.3	12.6
Commodity price risk programs \| Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 45.1	$ 57.8

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018
Income Taxes [Line Items]
Effective income tax rate		54.60%	54.60%		24.40%	24.40%		78.10%	78.10%
Increase (Decrease) in Effective Tax Rate		30.20%			53.70%
State regulatory proceedings, value	$ 0			$ 9.5			$ 127.8
Deferred Tax Assets, Operating Loss Carryforwards	602.1	$ 602.1	$ 602.1	765.9	$ 765.9	$ 765.9
Deferred Tax Assets, Charitable Contribution Carryforwards	7.8	7.8	7.8
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	1.5			0.6			0.4
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	0			22.6			0.2
Unrecognized Tax Benefits, Income Tax Penalties Expense	0			0			$ 0
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0	0	0	$ 0	$ 0	$ 0
Deferred Tax Assets, Valuation Allowance	6.4	6.4	6.4
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	520.8	520.8	520.8
State and Local Jurisdiction
Income Taxes [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 81.4	$ 81.4	$ 81.4

Income Taxes (Schedule Of Compo

Income Taxes (Schedule Of Components Of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
Federal	$ 0.2	$ 0	$ 0
State	11.7	5.2	8.2
Total Current	11.9	5.2	8.2
Deferred
Federal	(0.4)	110.7	(209.4)
State	(27.4)	9	22.2
Total Deferred	(27.8)	119.7	(187.2)
Deferred Investment Credits	(1.2)	(1.4)	(1)
Income Taxes	$ (17.1)	$ 123.5	$ (180)

Income Taxes (Schedule Of Reaso

Income Taxes (Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018
Schedule of Reasons Behind Differences in Computation of Total Income Taxes [Line Items]
Book income (loss) before income taxes	$ (31.3)			$ 506.6			$ (230.6)
Tax expense (benefit) at statutory federal income tax rate, value	(6.6)			106.5			(48.4)
Tax expense (benefit) at statutory federal income tax rate, rate		21.00%			21.00%			21.00%
Increases (reductions) in taxes resulting from:
State income taxes, net of federal income tax benefit, value	(11.7)			10.1			24.7
State income taxes, net of federal income tax benefit, rate		37.40%			2.00%			(10.70%)
Amortization of regulatory liabilities, value	(38.4)			(29.4)			(29.3)
Amortization of regulatory liabilities, rate		122.70%			(5.80%)			12.70%
Goodwill impairment, value	0			43			0
Goodwill impairment, rate		0.00%			8.50%			0.00%
Fines and penalties, value	11.8			11.5			0.2
Fines and penalties, rate		(37.70%)			2.30%			(0.10%)
Charitable contribution carryover, value	0			(2.5)			0
Charitable contribution carryover, rate		0.00%			(0.50%)			0.00%
State regulatory proceedings, value	0			(9.5)			(127.8)
State regulatory proceedings, rate		0.00%			(1.90%)			55.40%
Employee stock ownership plan dividends and other compensation, value	(1.3)			(2)			(2.2)
Employee stock ownership plan dividends and other compensation, rate		4.20%			(0.40%)			1.00%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount	23.3			0			0
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent		(0.745)			0			0
Effective Income Tax Rate Reconciliation Tax Accrual Adjustments	8.9			0			0
Effective Income Tax Rate Reconciliation, Tax Accrual Adjustments, Percent		(28.40%)			0.00%			0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	(2.5)			0			0
Effective Income Tax Rate Reconciliation, Tax Credit, Percent		8.00%			0.00%			0.00%
Other adjustments, value	(0.6)			(4.2)			2.8
Other adjustments, rate		1.90%			(0.80%)			(1.20%)
Income Taxes	$ (17.1)			$ 123.5			$ (180)
Income Taxes, rate		54.60%	54.60%		24.40%	24.40%		78.10%	78.10%

Income Taxes (Schedule Of Princ

Income Taxes (Schedule Of Principal Components Of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Liabilities
Accelerated depreciation and other property differences	$ 2,339.3	$ 2,516.9
Other regulatory assets	331.8	381.5
Total Deferred Tax Liabilities	2,671.1	2,898.4
Deferred Tax Assets
Other regulatory liabilities and deferred investment tax credits (including TCJA)	287.8	336.1
Pension and other postretirement/postemployment benefits	118.1	152.1
Net operating loss carryforward and AMT credit carryforward	602.1	765.9
Environmental liabilities	22.6	25.4
Other accrued liabilities	41.5	35.3
Other, net	128.4	98.3
Total Deferred Tax Assets	1,200.5	1,413.1
Net Deferred Tax Liabilities	$ 1,470.6	$ 1,485.3

Income Taxes (Schedule of Unrec

Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits - Opening Balance	$ 23.2	$ 1.2	$ 1.4
Gross decreases - tax positions in prior period	(1.5)	(0.6)	(0.4)
Gross increases - current period tax positions	0	22.6	0.2
Unrecognized Tax Benefits - Ending Balance	21.7	23.2	1.2
Offset for net operating loss carryforwards	(21.7)	(22.6)	0
Balance - Less Net Operating Loss Carryforwards	$ 0	$ 0.6	$ 1.2

Pension and Other Postretirem_3

Pension and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 1,930.5	$ 2,239.6
Regulatory Liabilities	$ 2,065.5	2,512.2
Expected return on plan assets	5.70%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 140.1	204.3
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.7	0.2	$ (0.4)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	17	47.6	$ 14.8
Employer contributions	2.9	2.9
Expected contribution	2.9
Defined Benefit Plan, Accumulated Benefit Obligation	2,036.8	2,111.5
Funded status of plan	$ (59.3)	$ 49.6
Expected return on plan assets	5.70%	6.10%	7.00%
Settlement loss	$ 10.5	$ 9.5	$ 18.5
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement	1.4
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	24.8	88.8
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(2.1)	(3.2)	(4)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	11.9	10	$ 7.5
Employer contributions	21.6	23
Expected contribution	21.8
Funded status of plan	$ 304.4	$ 315.1
Expected return on plan assets	5.67%	5.83%	5.80%
Settlement loss	$ 1.5	$ 0	$ 0
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0	0	$ 86.1
Percentage of investments	0.00%
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 583.3	739.1
Regulatory Liabilities	0	0.1
International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	230.1	205
International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	48.2	40.7
Commingled Funds \| Short-Term Money Markets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	78.8	14.8
Commingled Funds \| Short-Term Money Markets \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	7.6	7.7
Commingled Funds \| Short-Term Money Markets \| Significant Unobservable Inputs (Level 3) [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Commingled Funds \| Short-Term Money Markets \| Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Commingled Funds \| United States Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	279.7	305.9
Commingled Funds \| United States Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	14	12.1
Commingled Funds \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Commingled Funds \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Commingled Funds \| International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	176.8	148.1
Commingled Funds \| International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24.1	20.1
Commingled Funds \| International Equities \| Significant Unobservable Inputs (Level 3) [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Commingled Funds \| International Equities \| Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0	$ 0

Pension and Other Postretirem_4

Pension and Other Postretirement Benefits (Schedule Of Portfolio Asset Mix) (Details)	Dec. 31, 2020	Dec. 31, 2019
Minimum \| Domestic Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	12.00%	12.00%
Minimum \| Domestic Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Minimum \| International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	6.00%	6.00%
Minimum \| International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Minimum \| Fixed Income \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	59.00%
Minimum \| Fixed Income \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Minimum \| Real Estate [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Minimum \| Real Estate [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Minimum \| Real Estate \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Minimum \| Real Estate \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Minimum \| Short-Term Investments \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Minimum \| Short-Term Investments \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Minimum \| Private Equity \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Minimum \| Private Equity \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Maximum \| Domestic Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	32.00%	32.00%
Maximum \| Domestic Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	55.00%	55.00%
Maximum \| International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	16.00%	16.00%
Maximum \| International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	25.00%	25.00%
Maximum \| Fixed Income \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	71.00%
Maximum \| Fixed Income \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Maximum \| Real Estate [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	7.00%
Maximum \| Real Estate [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Maximum \| Real Estate \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		7.00%
Maximum \| Real Estate \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Maximum \| Short-Term Investments \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%	10.00%
Maximum \| Short-Term Investments \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%	10.00%
Maximum \| Private Equity \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%	5.00%
Maximum \| Private Equity \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%

Pension and Other Postretirem_5

Pension and Other Postretirement Benefits (Schedule of Plan Asset Mix Prior Year) (Details)	Dec. 31, 2020	Dec. 31, 2019
Pension Plan \| Domestic Equities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	12.00%	12.00%
Pension Plan \| Domestic Equities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	32.00%	32.00%
Pension Plan \| International Equities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	6.00%	6.00%
Pension Plan \| International Equities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	16.00%	16.00%
Pension Plan \| Fixed Income \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		59.00%
Pension Plan \| Fixed Income \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		71.00%
Pension Plan \| Real Estate \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Pension Plan \| Real Estate \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		7.00%
Pension Plan \| Short-Term Investments \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Pension Plan \| Short-Term Investments \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%	10.00%
Pension Plan \| Private Equity \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Pension Plan \| Private Equity \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%	5.00%
Other Postretirement Benefits \| Domestic Equities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Other Postretirement Benefits \| Domestic Equities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	55.00%	55.00%
Other Postretirement Benefits \| International Equities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Other Postretirement Benefits \| International Equities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	25.00%	25.00%
Other Postretirement Benefits \| Fixed Income \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		20.00%
Other Postretirement Benefits \| Fixed Income \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		100.00%
Other Postretirement Benefits \| Real Estate \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Other Postretirement Benefits \| Real Estate \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0.00%
Other Postretirement Benefits \| Short-Term Investments \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Other Postretirement Benefits \| Short-Term Investments \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%	10.00%
Other Postretirement Benefits \| Private Equity \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%
Other Postretirement Benefits \| Private Equity \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%	0.00%

Pension and Other Postretirem_6

Pension and Other Postretirement Benefits (Schedule Of Pension Plan And Postretirement Plan Asset Mix) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 2,404.1	$ 2,342.3
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	100.00%	100.00%
Pension Plan \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 2,117.7	$ 2,080.9	$ 1,867.7
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	100.00%	100.00%
Other Postretirement Benefits \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 286.4	$ 261.4	$ 216.3
Domestic Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 446.3	$ 446.4
Percentage of total asset	21.00%	21.50%
Domestic Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 108.8	$ 93.8
Percentage of total asset	38.00%	35.90%
International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 230.1	$ 205
Percentage of total asset	10.90%	9.90%
International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 48.2	$ 40.7
Percentage of total asset	16.80%	15.60%
Fixed Income \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 1,291.2	$ 1,337.2
Percentage of total asset	61.00%	64.20%
Fixed Income \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 122	$ 119.5
Percentage of total asset	42.60%	45.70%
Real Estate \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 52.9	$ 53.9
Percentage of total asset	2.50%	2.60%
Real Estate \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0	$ 0
Percentage of total asset	0.00%	0.00%
Cash/Other [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 97.2	$ 38.4
Percentage of total asset	4.60%	1.80%
Cash/Other [Member] \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 7.4	$ 7.4
Percentage of total asset	2.60%	2.80%
Commingled Funds \| Short-Term Money Markets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 78.8	$ 14.8
Commingled Funds \| Short-Term Money Markets \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	7.6	7.7
Commingled Funds \| International Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	176.8	148.1
Commingled Funds \| International Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24.1	20.1
Commingled Funds \| Fixed Income \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	337.6	351.8
Commingled Funds \| United States Equities \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	279.7	305.9
Commingled Funds \| United States Equities \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 14	$ 12.1

Pension and Other Postretirem_7

Pension and Other Postretirement Benefits (Schedule Of Fair Value Of Pension Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 436.3
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 480.4
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	934.4	968.6
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0	$ 86.1
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,404.1	2,342.3
Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	18.5
Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	12.5
Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	2.4
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	2,036.8	2,111.5
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	2,110.7	2,073
Defined Benefit Plan, Benefit Obligation	2,058.4	2,130.5	1,981.3
Defined Benefit Plan, Funded (Unfunded) Status of Plan	59.3	(49.6)
Pension Plan \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		204.1
Pension Plan \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	231.1
Pension Plan \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	936	971.4
Pension Plan \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	0	0
Pension Plan \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,117.7	2,080.9	1,867.7
Pension Plan \| Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	11.9	6.7
Pension Plan \| Cash [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		6.7
Pension Plan \| Cash [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	11.9
Pension Plan \| Cash [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Cash [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	230.1	205
Pension Plan \| Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,291.2	1,337.2
Pension Plan \| Equity Securities [Member] \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2.4
Pension Plan \| Equity Securities [Member] \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2.4
Pension Plan \| Equity Securities [Member] \| United States Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Equity Securities [Member] \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Fixed Income Securities [Member] \| Government
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	243.4	319.6
Pension Plan \| Fixed Income Securities [Member] \| Government \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Fixed Income Securities [Member] \| Government \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Fixed Income Securities [Member] \| Government \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	243.4	319.6
Pension Plan \| Fixed Income Securities [Member] \| Government \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Fixed Income Securities [Member] \| Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	692.6	651.8
Pension Plan \| Fixed Income Securities [Member] \| Corporate [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Fixed Income Securities [Member] \| Corporate [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Fixed Income Securities [Member] \| Corporate [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	692.6	651.8
Pension Plan \| Fixed Income Securities [Member] \| Corporate [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	176.8	148.1
Pension Plan \| Commingled Funds \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Commingled Funds \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Commingled Funds \| International Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| International Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	337.6	351.8
Pension Plan \| Commingled Funds \| Fixed Income \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Commingled Funds \| Fixed Income \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Commingled Funds \| Fixed Income \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| Fixed Income \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	279.7	305.9
Pension Plan \| Commingled Funds \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Commingled Funds \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Commingled Funds \| United States Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	78.8	14.8
Pension Plan \| Commingled Funds \| Short-Term Money Markets \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Commingled Funds \| Short-Term Money Markets \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Commingled Funds \| Short-Term Money Markets \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Commingled Funds \| Short-Term Money Markets \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	10.9	14
Pension Plan \| Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	6.6	8.5
Pension Plan \| Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0.3	0.5
Pension Plan \| Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	52.9	53.9
Pension Plan \| Real Estate [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Pension Plan \| Real Estate [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Real Estate [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Real Estate [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Mutual Funds [Member] \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	55.4	56.9
Pension Plan \| Mutual Funds [Member] \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		56.9
Pension Plan \| Mutual Funds [Member] \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	55.4
Pension Plan \| Mutual Funds [Member] \| International Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Mutual Funds [Member] \| International Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Mutual Funds [Member] \| U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	161.3	140.5
Pension Plan \| Mutual Funds [Member] \| U.S. Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		140.5
Pension Plan \| Mutual Funds [Member] \| U.S. Multi-Strategy [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	161.3
Pension Plan \| Mutual Funds [Member] \| U.S. Multi-Strategy [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Mutual Funds [Member] \| U.S. Multi-Strategy [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Pension Plan \| Mutual Funds [Member] \| Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0.1
Pension Plan \| Mutual Funds [Member] \| Fixed Income \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0.1
Pension Plan \| Mutual Funds [Member] \| Fixed Income \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Pension Plan \| Mutual Funds [Member] \| Fixed Income \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	286.4	261.4
Defined Benefit Plan, Benefit Obligation	590.8	576.5	492.5
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(304.4)	(315.1)
Other Postretirement Benefits \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		221.5
Other Postretirement Benefits \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	240.7
Other Postretirement Benefits \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	0	0
Other Postretirement Benefits \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	0	0
Other Postretirement Benefits \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	286.4	261.4	$ 216.3
Other Postretirement Benefits \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	48.2	40.7
Other Postretirement Benefits \| Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	122	119.5
Other Postretirement Benefits \| Due To Brokers Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	(1.6)	(2.8)
Other Postretirement Benefits \| Due To Brokers Net [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Due To Brokers Net [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Due To Brokers Net [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	(1.6)	(2.8)
Other Postretirement Benefits \| Due To Brokers Net [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Accrued Investment Income Dividends [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		10.7
Other Postretirement Benefits \| Accrued Investment Income Dividends [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		10.7
Other Postretirement Benefits \| Accrued Investment Income Dividends [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Accrued Investment Income Dividends [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Receivables/Payables [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	8.6
Other Postretirement Benefits \| Receivables/Payables [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	8.6
Other Postretirement Benefits \| Receivables/Payables [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Receivables/Payables [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Commingled Funds \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24.1	20.1
Other Postretirement Benefits \| Commingled Funds \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Commingled Funds \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Commingled Funds \| International Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Commingled Funds \| International Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Commingled Funds \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	14	12.1
Other Postretirement Benefits \| Commingled Funds \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Commingled Funds \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Commingled Funds \| United States Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Commingled Funds \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Commingled Funds \| Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	7.6	7.7
Other Postretirement Benefits \| Commingled Funds \| Short-Term Money Markets \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0
Other Postretirement Benefits \| Commingled Funds \| Short-Term Money Markets \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Postretirement Benefits \| Commingled Funds \| Short-Term Money Markets \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Commingled Funds \| Short-Term Money Markets \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24.1	20.6
Other Postretirement Benefits \| Mutual Funds [Member] \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		20.6
Other Postretirement Benefits \| Mutual Funds [Member] \| International Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	24.1
Other Postretirement Benefits \| Mutual Funds [Member] \| International Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| International Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	121.8	119.2
Other Postretirement Benefits \| Mutual Funds [Member] \| Fixed Income \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		119.2
Other Postretirement Benefits \| Mutual Funds [Member] \| Fixed Income \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	121.8
Other Postretirement Benefits \| Mutual Funds [Member] \| Fixed Income \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| Fixed Income \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	94.8	81.7
Other Postretirement Benefits \| Mutual Funds [Member] \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		81.7
Other Postretirement Benefits \| Mutual Funds [Member] \| United States Equities \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	94.8
Other Postretirement Benefits \| Mutual Funds [Member] \| United States Equities \| Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Postretirement Benefits \| Mutual Funds [Member] \| United States Equities \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Underfunded Plan [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	2,004.7	637.6
Defined Benefit Plan, Plan Assets, Amount	2,117.7	645.8
Defined Benefit Plan, Benefit Obligation	2,026.3	637.6
Defined Benefit Plan, Funded (Unfunded) Status of Plan	91.4	8.2
Underfunded Plan [Member] \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	32.1	1,473.9
Defined Benefit Plan, Plan Assets, Amount	0	1,435.1
Defined Benefit Plan, Benefit Obligation	32.1	1,492.9
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (32.1)	$ (57.8)

Pension and Other Postretirem_8

Pension and Other Postretirement Benefits (Schedule Of Changes In The Fair Value Of The Plan Level Three Assets) (Details) - Significant Unobservable Inputs (Level 3) [Member] $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 86.1
Fair value of plan assets at end of year	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	(86.1)
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	52.7
Fair value of plan assets at end of year	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	(52.7)
Private Equity Limited Partnerships [Member] \| U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	18.5
Fair value of plan assets at end of year	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	(18.5)
Private Equity Limited Partnerships [Member] \| International Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	12.5
Fair value of plan assets at end of year	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	(12.5)
Private Equity Limited Partnerships [Member] \| Distressed Opportunities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	2.4
Fair value of plan assets at end of year	0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Assets Transferred into (out of) Level 3	$ (2.4)

Pension and Other Postretirem_9

Pension and Other Postretirement Benefits (Schedule of Net Asset Value Per Share) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 918.6	$ 860.5
Commingled Funds \| Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 86.4	$ 22.5
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Daily	Daily
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	1 day	1 day
Commingled Funds \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 293.7	$ 318
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Daily	Monthly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period		3 days
Commingled Funds \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 200.9	$ 168.2
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Monthly	Monthly
Commingled Funds \| Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 337.6	$ 351.8
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Daily	Daily
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	3 days	3 days
Minimum \| Commingled Funds \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	1 day
Minimum \| Commingled Funds \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	10 days	10 days
Maximum \| Commingled Funds \| United States Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	5 days
Maximum \| Commingled Funds \| International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	30 days	30 days

Pension and Other Postretire_10

Pension and Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Noncurrent liabilities	$ (303.5)	$ (314.3)
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	2,342.3
Fair value of plan assets at end of year	2,404.1	2,342.3
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	2,130.5	1,981.3
Service cost	32	29.2	$ 31.3
Interest cost	51.6	72.3	67.1
Plan participants' contributions	0	0
Plan amendments	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	140.1	204.3
Defined Benefit Plan, Benefit Obligation, Benefits Paid	174.5	156.6
Benefits paid	(174.6)	(156.5)
Spinoff to Eversource	121.4	0
Estimated benefits paid by incurred subsidy	0	0
Projected benefit obligation at end of year	2,058.4	2,130.5	1,981.3
Actual return on plan assets	329.9	366.8
Employer contributions	2.9	2.9
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	59.3	(49.6)
Noncurrent assets	91.4	8.2
Current liabilities	(2.9)	(3)
Noncurrent liabilities	(29.2)	(54.8)
Net amount recognized at end of year	59.3	(49.6)
Unrecognized prior service cost	0.3	3
Unrecognized actuarial loss	497.2	652.8
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	497.5	655.8
Pension Plan \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	2,080.9	1,867.7
Fair value of plan assets at end of year	2,117.7	2,080.9	1,867.7
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	576.5	492.5
Service cost	6.6	5.1	5
Interest cost	15.4	19.2	17.6
Plan participants' contributions	4.1	4.8
Plan amendments	0	5.1
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	24.8	88.8
Defined Benefit Plan, Benefit Obligation, Benefits Paid	37	39.5
Benefits paid	(37)	(39.5)
Spinoff to Eversource	0	0
Estimated benefits paid by incurred subsidy	0.4	0.5
Projected benefit obligation at end of year	590.8	576.5	492.5
Actual return on plan assets	36.3	56.9
Employer contributions	21.6	23
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	4.1	4.7
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(304.4)	(315.1)
Noncurrent assets	0	0
Current liabilities	(0.9)	(0.8)
Net amount recognized at end of year	(304.4)	(315.1)
Unrecognized prior service cost	(10.1)	(10.7)
Unrecognized actuarial loss	116.4	118.4
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	106.3	107.7
Other Postretirement Benefits \| Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	261.4	216.3
Fair value of plan assets at end of year	$ 286.4	$ 261.4	$ 216.3

Pension and Other Postretire_11

Pension and Other Postretirement Benefits (Schedule of Benefit Obligations in Excess of Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 2,036.8	$ 2,111.5
Defined Benefit Plan, Benefit Obligation	2,058.4	2,130.5	$ 1,981.3
Defined Benefit Plan, Funded (Unfunded) Status of Plan	59.3	(49.6)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	140.1	204.3
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	(121.3)	0
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation	590.8	576.5	$ 492.5
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(304.4)	(315.1)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	24.8	88.8
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change	0	0
Underfunded Plan [Member] \| Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	32.1	1,473.9
Defined Benefit Plan, Benefit Obligation	32.1	1,492.9
Defined Benefit Plan, Plan Assets, Amount	0	1,435.1
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (32.1)	$ (57.8)

Pension and Other Postretire_12

Pension and Other Postretirement Benefits (Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.38%	3.12%
Rate of Compensation Increases	4.00%	4.00%
Trend for Next Year	0.00%	0.00%
Ultimate Trend	0.00%	0.00%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	4.00%	4.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.49%	3.21%
Rate of Compensation Increases	0.00%	0.00%
Trend for Next Year	6.69%	6.68%
Ultimate Trend	4.50%	4.50%
Year Ultimate Trend Reached	2029	2028
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	0.00%	0.00%

Pension and Other Postretire_13

Pension and Other Postretirement Benefits (Schedule Of Expected Payments To Participants In Pension Plan) (Details) $ in Millions	Dec. 31, 2020USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2017	$ 218.8
2018	154.5
2019	149.2
2020	145.9
2021	141.3
2022-2026	621.9
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2017	38.4
2018	37.8
2019	37.3
2020	37
2021	36.6
2022-2026	172.1
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
2017	0.4
2018	0.4
2019	0.4
2020	0.4
2021	0.3
2022-2026	$ 1.2

Pension and Other Postretire_14

Pension and Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 32	$ 29.2	$ 31.3
Interest cost	51.6	72.3	67.1
Expected return on assets	(111.6)	(108.8)	(142.3)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.7	0.2	(0.4)
Recognized actuarial loss	33.8	45.2	40.6
Settlement loss	10.5	9.5	18.5
Total Net Periodic Benefits Cost	17	47.6	14.8
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	6.6	5.1	5
Interest cost	15.4	19.2	17.6
Expected return on assets	(14.4)	(13.1)	(14.9)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(2.1)	(3.2)	(4)
Recognized actuarial loss	4.9	2	3.8
Settlement loss	1.5	0	0
Total Net Periodic Benefits Cost	$ 11.9	$ 10	$ 7.5

Pension and Other Postretire_15

Pension and Other Postretirement Benefits (Schedule Of Key Assumptions That Were Used To Calculate The Net Periodic Benefits Cost) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return on Plan Assets	5.70%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.39%	4.48%	3.79%
Defined Benefit Plan Assumptions Used In Calculating Net Periodic Cost Discount Rate for Interest Cost	2.65%	3.84%	3.15%
Expected Long-Term Rate of Return on Plan Assets	5.70%	6.10%	7.00%
Rate of Compensation Increases	4.00%	4.00%	4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate	4.00%	4.00%	4.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.52%	4.59%	3.89%
Defined Benefit Plan Assumptions Used In Calculating Net Periodic Cost Discount Rate for Interest Cost	2.76%	3.94%	3.27%
Expected Long-Term Rate of Return on Plan Assets	5.67%	5.83%	5.80%
Rate of Compensation Increases	0.00%	0.00%	0.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate	0.00%	0.00%	0.00%

Pension and Other Postretire_16

Pension and Other Postretirement Benefits (Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Net prior service cost/(credit)	$ 0	$ 0
Net actuarial (gain)/loss	(78.2)	(53.8)
Settlements	(10.5)	(9.5)	$ (18.5)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(0.7)	(0.2)	0.4
Less: amortization of net actuarial (gain) loss	(33.8)	(45.2)	(40.6)
Gain Attributable to spinoff to Eversource	(33.1)	0
Prior Service Cost attributable to spinoff to Eversource	(2)	0
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability	(158.3)	(108.7)
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability	(141.3)	(61.1)
Other Postretirement Benefits
Net prior service cost/(credit)	0	5.1
Net actuarial (gain)/loss	2.9	45.1
Settlements	(1.5)	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	2.1	3.2	4
Less: amortization of net actuarial (gain) loss	(4.9)	(2)	$ (3.8)
Gain Attributable to spinoff to Eversource	0	0
Prior Service Cost attributable to spinoff to Eversource	0	0
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability	(1.4)	51.4
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability	$ 10.5	$ 61.4

Equity (Narrative) (Details)

Equity (Narrative) (Details) $ / shares in Units, $ in Millions	Dec. 15, 2020USD ($)$ / shares	Sep. 16, 2020$ / sharesshares	Dec. 11, 2019USD ($)$ / shares	Nov. 21, 2019USD ($)$ / shares	Aug. 01, 2019	Dec. 10, 2018$ / sharesshares	Nov. 06, 2018USD ($)$ / shares	Nov. 01, 2018USD ($)	Jun. 11, 2018USD ($)	May 04, 2018USD ($)$ / sharesshares	May 03, 2017USD ($)	Sep. 03, 2020$ / sharesshares	Sep. 13, 2019$ / sharesshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Jun. 15, 2023$ / shares	Dec. 05, 2018shares	Dec. 31, 2017shares
Forward Contract Indexed to Issuer's Equity [Line Items]
Common stock, shares authorized \| shares															600,000,000	600,000,000
Preferred Stock, Shares Authorized \| shares															20,000,000	20,000,000
Common Stock, Shares, Outstanding \| shares															391,760,051	382,135,680
Preferred Stock, Shares Outstanding \| shares															440,000	440,000
Common Stock, Dividends, Per Share, Declared \| $ / shares															$ 0.84	$ 0.80	$ 0.78
Shares, Issued \| shares														372,363,000	391,760,000	382,136,000	372,363,000			337,016,000
Common stock, par value \| $ / shares															$ 0.01	$ 0.01
Proceeds from Issuance of Preferred Stock and Preference Stock \| $															$ 0	$ 0	$ 880
Preferred Stock, Par or Stated Value Per Share \| $ / shares															$ 0.01	$ 0.01
Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Shares Outstanding \| shares															400,000
Preferred Stock, Shares Issued \| shares															400,000
Preferred Stock, Dividend Rate, Percentage									5.65%
Preferred Stock, Liquidation Preference Per Share \| $ / shares															$ 1,000
Preferred Stock, Dividend Rate, Initial Margin									2.843%
Preferred Stock, Dividend Rate, Initial Margin Plus 1.000%									1.00%
Preferred Stock, Amount of Preferred Dividends in Arrears \| $															$ 1
Preferred Stock, Per Share Amounts of Preferred Dividends in Arrears \| $ / shares															$ 2.51
Preferred Stock, Liquidation Preference, Value \| $															$ 400
Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Shares Outstanding \| shares															20,000
Preferred Stock, Dividend Rate, Percentage														6.50%
Preferred Stock, Liquidation Preference Per Share \| $ / shares															$ 25,000
Preferred Stock, Dividend Rate, Initial Margin														3.632%
Preferred Stock, Dividend Rate, Initial Margin Plus 1.000%														1.00%
Preferred Stock, Amount of Preferred Dividends in Arrears \| $															$ 1.4
Preferred Stock, Per Share Amounts of Preferred Dividends in Arrears \| $ / shares															$ 72.23
Preferred Stock Depositary Shares Issued \| shares																			20,000,000
Preferred Stock, Liquidation Preference, Value \| $															$ 500
Depositary Stock Liquidation Preference \| $ / shares															$ 25
Series B-1 Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Shares Issued \| shares															20,000
Gross Proceeds \| Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock \| $									$ 400
Gross Proceeds \| Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock \| $														$ 500
Common Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares, Issued \| shares										24,964,163				376,326,000	395,723,000	386,099,000	376,326,000			340,813,000
Common stock, par value \| $ / shares										$ 0.01
Sale of Stock, Price Per Share \| $ / shares										$ 24.28
Common Stock \| Gross Proceeds
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement \| $										$ 606
Common Stock \| Net Proceeds
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement \| $										$ 599.6
At The Market Program
Forward Contract Indexed to Issuer's Equity [Line Items]
Number Of Equity Distribution Agreements					4			5			4
Common Stock Aggregate Sale Price \| $								$ 500			$ 500				$ 434.4
Derivative, Forward Price \| $ / shares						$ 26.55
Forward Contract Indexed to Issuer's Equity, Shares \| shares						4,708,098
Forward Agreement
Forward Contract Indexed to Issuer's Equity [Line Items]
Derivative, Forward Price \| $ / shares	$ 22.77		$ 28.83	$ 26.01			$ 26.43
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value \| $	$ 64		$ 107.1	$ 122.5			$ 167.7
Forward Agreement 19
Forward Contract Indexed to Issuer's Equity [Line Items]
Derivative, Forward Price \| $ / shares													$ 29.26
Forward Contract Indexed to Issuer's Equity, Shares \| shares													3,714,400
Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares, Issued \| shares														420,000	440,000	440,000	420,000			0
Preferred Stock \| Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock \| $									$ 393.9
Preferred Stock \| Net Proceeds \| Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock \| $														$ 486.1
Forward August 20 [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Derivative, Forward Price \| $ / shares												$ 23.25
Forward Contract Indexed to Issuer's Equity, Shares \| shares												2,809,029
Forward September 20 [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Derivative, Forward Price \| $ / shares	$ 21.82	$ 22.28
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value \| $	$ 31.7
Forward Contract Indexed to Issuer's Equity, Shares \| shares		1,452,102
Subsequent Event \| Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Liquidation Preference Per Share \| $ / shares																		$ 1,000

Equity (Schedule of Stock Offer

Equity (Schedule of Stock Offering Program) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
At The Market Stock Offering [Line Items]
Stock Issued During Period, Shares, New Issues			24,964,000
Proceeds, net of fees (in millions)	$ 211.4	$ 244.4	$ 848.2
At The Market Program
At The Market Stock Offering [Line Items]
Stock Issued During Period, Shares, New Issues	8,459,430	8,422,498	8,883,014
Common Stock Issued Average Price Per Share	$ 23.60	$ 27.75	$ 26.85
Proceeds, net of fees (in millions)	$ 196.5	$ 229.1	$ 232.5

Equity (Schedule of Stock by Cl

Equity (Schedule of Stock by Class - Preferred) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	440,000	440,000
Preferred Stock, Dividends Per Share, Declared			$ 28.88
Preferred Stock, Value, Outstanding	$ 880	$ 880
Series A Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share	$ 1,000
Preferred Stock, Shares Outstanding	400,000
Preferred Stock, Dividends Per Share, Declared	$ 56.50	$ 56.50	28.88
Preferred Stock, Value, Outstanding	$ 393.9	$ 393.9
Series B Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share	$ 25,000
Preferred Stock, Shares Outstanding	20,000
Preferred Stock, Dividends Per Share, Declared	$ 1,625	$ 1,674.65	$ 0
Preferred Stock, Value, Outstanding	$ 486.1	$ 486.1

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended			36 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 12, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for awards, shares							10,000,000
Common stock reserved for future awards, shares	10,007,832					10,007,832
Stock-based employee compensation expense	$ 13.5	$ 16.3	$ 15.2
Related tax benefits	3.3	4	3.7
Excess Tax Benefit from Share-based Compensation, Operating Activities		0.8	1
Unrecognized compensation cost related to nonvested awards	$ 19.1					$ 19.1
Weighted-average remaining requisite service period, years	1 year 10 months 24 days
RTSR Modifier	25.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%
401(k) match, profit sharing and non-elective expense	$ 37.8	$ 37.5	$ 37.6
Excess Tax Expense - Share Based Compensation	$ 0.4
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	235,100
Shares nonvested	478,227	302,606				478,227
Shares vesting period, (years)						3 years
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	528,729	552,389	514,338
Shares nonvested	1,384,336	1,503,251				1,384,336
Performance Shares \| NOEPS
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares granted	$ 11.7	$ 11.7	$ 9.2
Performance Shares \| CVI
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares granted	$ 2.6	$ 2.5	$ 2.4
Omnibus Plan \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	210,273
Director Plan \| Non-Employee Director Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	67,806					67,806
2018 Award \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted			158,689
Fair value of shares granted			$ 3.5
Shares nonvested	119,333					119,333
2018 Award \| Performance Shares \| NOEPS
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	347,479					347,479
2018 Award \| Performance Shares \| CVI
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	80,185					80,185
2019 Award \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted		166,031
Fair value of shares granted		$ 4.1
Shares nonvested	135,170					135,170
2019 Award \| Performance Shares \| NOEPS
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	384,680					384,680
2019 Award \| Performance Shares \| CVI
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	88,769					88,769
2020 award \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	235,100
Fair value of shares granted	$ 6.1
Shares nonvested	223,724					223,724
2020 award \| Performance Shares \| NOEPS
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	392,619					392,619
2020 award \| Performance Shares \| CVI
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	90,604					90,604
Subsequent Event \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period, (years)				3 years	3 years
Subsequent Event \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period, (years)					3 years

Share-Based Compensation (Sched

Share-Based Compensation (Schedule Of Transactions Of Restricted Stock Unit) (Details) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Other Than Options \| shares	302,606
Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 23.49
Granted, Other Than Options \| shares	235,100
Granted, Weighted Average Grant Date Fair Value \| $ / shares	$ 25.77
Forfeited, Other Than Options \| shares	(38,220)
Forfeited, Weighted Average Grant Date Fair Value \| $ / shares	$ 24.18
Vested, Other Than Options \| shares	(21,259)
Vested, Weighted Average Grant Date Fair Value \| $ / shares	$ 24.68
Nonvested, Other Than Options \| shares	478,227
Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 24.51

Share-Based Compensation (Sch_2

Share-Based Compensation (Schedule Of Transactions Of Contingent Awards) (Details) - Performance Shares - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Other Than Options	1,503,251
Nonvested, Weighted Average Grant Date Fair Value	$ 22.74
Granted, Other Than Options	528,729	552,389	514,338
Granted, Weighted Average Grant Date Fair Value	$ 27.01
Forfeited, Other Than Options	(118,716)
Forfeited, Weighted Average Grant Date Fair Value	$ 25.63
Vested, Other Than Options	(528,928)
Vested, Weighted Average Grant Date Fair Value	$ 28.30
Nonvested, Other Than Options	1,384,336	1,503,251
Nonvested, Weighted Average Grant Date Fair Value	$ 25.09	$ 22.74

Share-Based Compensation (Sch_3

Share-Based Compensation (Schedule of Performance Award Details) (Details) - Performance Shares - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,384,336	1,503,251
NOEPS
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 11.7	$ 11.7	$ 9.2
NOEPS \| 2020 award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	392,619
NOEPS \| 2019 Award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	384,680
NOEPS \| 2018 Award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	347,479
CVI
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 2.6	$ 2.5	$ 2.4
CVI \| 2020 award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	90,604
CVI \| 2019 Award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	88,769
CVI \| 2018 Award
Performance Share Details [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	80,185

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	Aug. 18, 2020	Apr. 13, 2020	Aug. 12, 2019	Sep. 30, 2020	Aug. 31, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2019
Debt Instrument [Line Items]
Debt Instrument Tendered					$ 969.3
Loss on early extinguishment of long-term debt						$ 243.4	$ (243.5)	$ 0	$ (45.5)
Debt Instrument, Convertible, Conversion Ratio							62.50%
Security interest and other subset of asset							$ 150
Asset sale covenant percentage of consolidated total assets							10.00%
Cross default provision on default relating to any indebtedness							$ 50
Percentage of additional subset of assets capped							10.00%
Working Capital Adjustment				$ 5.3		$ 5.3
Senior Notes
Debt Instrument [Line Items]
Face amount of notes		$ 1,000
Columbia Of Massachusetts \| 6.30% Notes Due 2028
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate							6.37%	630.00%
Maximum
Debt Instrument [Line Items]
Cross default provision on default relating to any indebtedness							$ 50
Minimum
Debt Instrument [Line Items]
Cross default provision on default relating to any indebtedness							$ 5
5.85% Notes Due 2019
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount										$ 41
Interest rate on debt										5.85%
2.95% Notes Due 2029
Debt Instrument [Line Items]
Interest rate on debt			2.95%
2.95% Notes Due 2029 \| Senior Notes
Debt Instrument [Line Items]
Face amount of notes			$ 750
Proceeds from Debt, Net of Issuance Costs			$ 742.4
3.65% Notes Due 2023
Debt Instrument [Line Items]
Interest rate on debt				3.65%	3.65%	3.65%
0.95% Notes Due 2025
Debt Instrument [Line Items]
Interest rate on debt	0.95%
0.95% Notes Due 2025 \| Senior Notes
Debt Instrument [Line Items]
Face amount of notes	$ 1,250
3.60% Notes Due 2030
Debt Instrument [Line Items]
Interest rate on debt		3.60%
3.60% Notes Due 2030 \| Senior Notes
Debt Instrument [Line Items]
Proceeds from Debt, Net of Issuance Costs		$ 987.8
1.70% Notes Due 2031
Debt Instrument [Line Items]
Interest rate on debt	1.70%
1.70% Notes Due 2031 \| Senior Notes
Debt Instrument [Line Items]
Face amount of notes	$ 750
0.95% Notes Due 2025 and 1.70% Notes Due 2031 [Member] \| Senior Notes
Debt Instrument [Line Items]
Proceeds from Debt, Net of Issuance Costs	$ 1,980.4
4.45% Notes Due 2021
Debt Instrument [Line Items]
Interest rate on debt				4.45%	4.45%	4.45%
2.65% Notes Due 2022
Debt Instrument [Line Items]
Interest rate on debt				2.65%	2.65%	2.65%
3.85% Notes Due 2023
Debt Instrument [Line Items]
Interest rate on debt				3.85%	3.85%	3.85%
6.25% Notes Due 2040
Debt Instrument [Line Items]
Interest rate on debt					6.25%
5.95% Notes Due 2041
Debt Instrument [Line Items]
Interest rate on debt					5.95%
5.89% Notes Due 2025
Debt Instrument [Line Items]
Interest rate on debt				5.89%		5.89%
Senior Note Redeemed August & September 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount				$ 609.3		$ 609.3
Loss on early extinguishment of long-term debt				231.8
Note Redeemed September 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount				25		$ 25
Loss on early extinguishment of long-term debt				$ 11.7
6.26% Notes Due 2028 [Member]
Debt Instrument [Line Items]
Interest rate on debt				6.26%		6.26%
Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio							70.00%
Private Placement [Member] \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio							75.00%

Long-Term Debt (Schedule of Con

Long-Term Debt (Schedule of Consolidated Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Senior Notes	$ 9,003	$ 7,581.6
Medium-Term Notes	132	157
Capital Lease Obligations	195	201.5
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(86.9)	(70.5)
Long-term Debt, Excluding Current Maturities	$ 9,243.1	7,869.6
NiSource \| 4.45% Notes Due 2021
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2021
Debt, Weighted Average Interest Rate	4.45%
Senior Notes	$ 0	63.6
NiSource \| 2.65% Notes Due 2022
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 30, 2022
Debt, Weighted Average Interest Rate	2.65%
Senior Notes	$ 0	500
NiSource \| 3.85% Notes Due 2023
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 28, 2023
Debt, Weighted Average Interest Rate	3.85%
Senior Notes	$ 0	250
NiSource \| 3.65% Notes Due 2023
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Jun. 30, 2023
Debt, Weighted Average Interest Rate	3.65%
Senior Notes	$ 0	350
NiSource \| 0.95% Notes Due 2025
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	0.95%
Senior Notes	$ 1,250	0
NiSource \| 5.89% Notes Due 2025
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 30, 2025
Debt, Weighted Average Interest Rate	5.89%
Senior Notes	$ 0	265
NiSource \| 3.49% Notes due 2027
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	May 31, 2027
Debt, Weighted Average Interest Rate	3.49%
Senior Notes	$ 1,000	1,000
NiSource \| 6.78% Notes Due 2027
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2027
Debt, Weighted Average Interest Rate	6.78%
Senior Notes	$ 3	3
NiSource \| 2.95% Notes Due 2029
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Sep. 30, 2029
Debt, Weighted Average Interest Rate	2.95%
Senior Notes	$ 750	750
NiSource \| 3.60% Notes Due 2030
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	3.60%
Senior Notes	$ 1,000	0
NiSource \| 1.70% Notes Due 2031
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	1.70%
Senior Notes	$ 750	0
NiSource \| 6.25% Notes Due 2040
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2040
Debt, Weighted Average Interest Rate	6.25%
Senior Notes	$ 152.6	250
NiSource \| 5.95% Notes Due 2041
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Jun. 30, 2041
Debt, Weighted Average Interest Rate	5.95%
Senior Notes	$ 347.4	400
NiSource \| 5.80% Notes Due 2042
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 28, 2042
Debt, Weighted Average Interest Rate	5.80%
Senior Notes	$ 250	250
NiSource \| 5.25% Notes Due 2043
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 28, 2043
Debt, Weighted Average Interest Rate	5.25%
Senior Notes	$ 500	500
NiSource \| 4.80% Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 29, 2044
Debt, Weighted Average Interest Rate	4.80%
Senior Notes	$ 750	750
NiSource \| 5.65% Notes Due 2045
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 28, 2045
Debt, Weighted Average Interest Rate	5.65%
Senior Notes	$ 500	500
NiSource \| 4.375% Notes due 2047
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	May 31, 2047
Debt, Weighted Average Interest Rate	4.38%
Senior Notes	$ 1,000	1,000
NiSource \| 3.95% Notes Due 2048
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Mar. 31, 2048
Debt, Weighted Average Interest Rate	3.95%
Senior Notes	$ 750	750
NiSource \| 7.99% Notes Due 2027
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	7.99%
Medium-Term Notes	$ 49	$ 49
NiSource \| 7.99% Notes Due 2027 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	May 31, 2027
NiSource \| 7.99% Notes Due 2027 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Apr. 30, 2022
Columbia Of Massachusetts \| 6.30% Notes Due 2028
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	6.37%	630.00%
Medium-Term Notes	$ 15	$ 40
Columbia Of Massachusetts \| 6.30% Notes Due 2028 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Feb. 28, 2028
Columbia Of Massachusetts \| 6.30% Notes Due 2028 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2025
Columbia Of Massachusetts \| 5.49% notes Due 2043
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	0.00%
Capital Lease Obligations	$ 0	44.3
Columbia Of Massachusetts \| 5.49% notes Due 2043 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 30, 2043
Columbia Of Massachusetts \| 5.49% notes Due 2043 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Dec. 31, 2033
NIPSCO \| 7.61% Notes Due 2027
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	7.61%
Medium-Term Notes	$ 68	68
NIPSCO \| 7.61% Notes Due 2027 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Aug. 31, 2027
NIPSCO \| 7.61% Notes Due 2027 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Aug. 31, 2022
NIPSCO \| 1.79% Notes Due 2028
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	1.79%
Capital Lease Obligations	$ 16	0
NIPSCO \| 5.85% Notes Due 2019 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Apr. 30, 2019
Columbia Of Ohio \| 6.16% Notes Due 2044
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	6.16%
Capital Lease Obligations	$ 91.2	94.8
Columbia Of Ohio \| 6.16% Notes Due 2044 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Mar. 31, 2044
Columbia Of Ohio \| 6.16% Notes Due 2044 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Oct. 31, 2021
NiSource Corporate Services \| 3.47% Notes Due 2023
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	2.19%
Capital Lease Obligations	$ 49.4	22.3
NiSource Corporate Services \| 3.47% Notes Due 2023 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 30, 2023
NiSource Corporate Services \| 3.47% Notes Due 2023 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Jan. 31, 2020
Columbia Of Virginia \| 6.31% Notes Due 2039
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	6.30%
Capital Lease Obligations	$ 18.4	19.1
Columbia Of Virginia \| 6.31% Notes Due 2039 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Nov. 30, 2039
Columbia Of Virginia \| 6.31% Notes Due 2039 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Jul. 31, 2029
Columbia Of Kentucky \| 3.79% Notes Due 2027
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	May 31, 2027
Debt, Weighted Average Interest Rate	3.79%
Capital Lease Obligations	$ 0.3	0.3
Columbia Of Pennsylvania \| 5.67% Notes Due 2035
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	5.65%
Capital Lease Obligations	$ 19.7	$ 20.7
Columbia Of Pennsylvania \| 5.67% Notes Due 2035 \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	May 31, 2035
Columbia Of Pennsylvania \| 5.67% Notes Due 2035 \| Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Aug. 31, 2027

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) - USD ($) $ in Millions	Apr. 17, 2019	Dec. 31, 2020	Apr. 01, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Commercial paper outstanding		$ 503		$ 570
Line of Credit Facility, Amount Outstanding		0		0
Accounts receivable securitization facility borrowings		0		353.2
Commercial Paper
Short-term Debt [Line Items]
Revolving credit facility, maximum		1,500
Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, maximum		1,850
Term Loan
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.60%
Term Loan		$ 0		$ 850
Maximum \| Term Loan
Short-term Debt [Line Items]
Term Loan	$ 850		$ 850

Short-Term Borrowings (Schedule

Short-Term Borrowings (Schedule Of Short-Term Borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Commercial Paper weighted-average interest rate of 0.27% and 2.03% at December 31, 2020 and 2019, respectively	$ 503	$ 570
Accounts receivable securitization facility borrowings	0	353.2
Total short-term borrowings	$ 503	$ 1,773.2
Commercial Paper
Short-term Debt [Line Items]
Commercial Paper/credit facilities borrowings, weighted average interest rate	0.27%	2.03%
Term Loan
Short-term Debt [Line Items]
Term loan interest rate of 2.40% at December 31, 2019	$ 0	$ 850
Commercial Paper/credit facilities borrowings, weighted average interest rate		2.40%

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Leases (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 39.9		$ 64.2	$ 57
Lessee, Lease Renewal Term	25 years
Lessee, Operating Lease, Renewal Term	1 year
Lessee, Finance Lease, Term of Contract	4 years
Payments made in connection with operating leases		$ 49.1
Fleet Lease
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Minimum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Minimum \| Office Lease
Lessee, Lease, Description [Line Items]
Remaining Lease Term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	2 years
Maximum \| Office Lease
Lessee, Lease, Description [Line Items]
Remaining Lease Term	23 years

Leases (Lease Cost) (Details)

Leases (Lease Cost) (Details) - USD ($) $ in Millions	12 Months Ended
Leases (Lease Cost) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finance lease cost
Amortization of right-of-use assets	$ 23.4	$ 15.5
Interest on lease liabilities	11.1	11.3
Total finance lease cost	34.5	26.8
Operating lease cost	20.3	17.9
Short-term lease cost	0	1
Total lease cost	$ 54.8	$ 45.7

Leases (Right-of-Use Assets and

Leases (Right-of-Use Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:NetPropertyPlantandEquipment	us-gaap:NetPropertyPlantandEquipment
Finance Lease, Right-of-Use Asset	$ 176.8	$ 179.5
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:DeferredChargesAndOther	us-gaap:DeferredChargesAndOther
Operating Lease, Right-of-Use Asset	$ 39.9	$ 64.2	$ 57
Total leased assets	$ 216.7	$ 243.7
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:Currentportionoflong-termdebt	us-gaap:Currentportionoflong-termdebt
Finance Lease, Liability, Current	$ 23.3	$ 13.4
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherAccruals	us-gaap:OtherAccruals
Operating Lease, Liability, Current	$ 10.3	$ 13.2
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:Long-termDebtExcludingAmountsDueWithinOneYear	us-gaap:Long-termDebtExcludingAmountsDueWithinOneYear
Finance Lease, Liability, Noncurrent	$ 171.7	$ 188.1
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherNoncurrentLiabilities	us-gaap:OtherNoncurrentLiabilities
Operating Lease, Liability, Noncurrent	$ 29.9	$ 51.6
Total Lease Liability	$ 235.2	$ 266.3

Leases (Lease Information) (Det

Leases (Lease Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Finance Lease, Interest Payment on Liability	$ 11.1	$ 11.3
Operating Lease, Payments	20.2	17.9
Finance Lease, Principal Payments	18.4	10.6
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	59.3	26.4
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 10.9	$ 13.4
Finance Lease, Weighted Average Remaining Lease Term	11 years 2 months 12 days	14 years 9 months 18 days
Operating Lease, Weighted Average Remaining Lease Term	8 years	9 years 2 months 12 days
Finance Lease, Weighted Average Discount Rate, Percent	5.10%	5.90%
Operating Lease, Weighted Average Discount Rate, Percent	4.00%	4.30%

Leases (Lease Maturity) (Detail

Leases (Lease Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Lease Maturity [Line Items]
Total Future Minimum Lease Payments Due, Next Twelve Months	$ 44.4
Total Future Minimum Lease Payments, Due in Two Years	37.4
Total Future Minimum Lease Payments, Due in Three Years	33.5
Total Future Minimum Lease Payments, Due in Four Years	25.3
Total Future Minimum Lease Payments, Due in Five Years	19.8
Total Future Minimum Lease Payments, Due Thereafter	152.3
Total Future Minimum Lease Payments Due	312.7
Undiscounted Excess Amount	(77.5)
Total Lease Liability	235.2	$ 266.3
Short-term Lease Liability	33.6
Long-term Lease Liability	201.6
Finance Leases, Future Minimum Payments Due, Next Twelve Months	32.7
Finance Leases, Future Minimum Payments Due in Two Years	32.2
Finance Leases, Future Minimum Payments Due in Three Years	28.8
Finance Leases, Future Minimum Payments Due in Four Years	20.8
Finance Leases, Future Minimum Payments Due in Five Years	16.1
Finance Leases, Future Minimum Payments Due Thereafter	134.1
Finance Lease, Liability, Payment, Due	264.7
Finance Lease, Liability, Current	23.3	13.4
Finance Lease, Liability, Noncurrent	171.7	188.1
Operating Leases, Future Minimum Payments Due, Next Twelve Months	11.7
Operating Leases, Future Minimum Payments, Due in Two Years	5.2
Operating Leases, Future Minimum Payments, Due in Three Years	4.7
Operating Leases, Future Minimum Payments, Due in Four Years	4.5
Operating Leases, Future Minimum Payments, Due in Five Years	3.7
Operating Leases, Future Minimum Payments, Due Thereafter	18.2
Lessee, Operating Lease, Liability, Payments, Due	48
Operating Lease, Liability, Current	10.3	13.2
Operating Lease, Liability, Noncurrent	29.9	$ 51.6
Finance Lease
Lease Maturity [Line Items]
Finance Leases, Future Minimum Payments Due, Next Twelve Months	32.7
Finance Leases, Future Minimum Payments Due in Two Years	32.2
Finance Leases, Future Minimum Payments Due in Three Years	28.8
Finance Leases, Future Minimum Payments Due in Four Years	20.8
Finance Leases, Future Minimum Payments Due in Five Years	16.1
Finance Leases, Future Minimum Payments Due Thereafter	134.1
Finance Lease, Liability, Payment, Due	264.7
Finance Lease, Liability, Undiscounted Excess Amount	(69.7)
Finance Lease, Liability	195
Finance Lease, Liability, Current	23.3
Finance Lease, Liability, Noncurrent	171.7
Operating Lease
Lease Maturity [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	11.7
Operating Leases, Future Minimum Payments, Due in Two Years	5.2
Operating Leases, Future Minimum Payments, Due in Three Years	4.7
Operating Leases, Future Minimum Payments, Due in Four Years	4.5
Operating Leases, Future Minimum Payments, Due in Five Years	3.7
Operating Leases, Future Minimum Payments, Due Thereafter	18.2
Lessee, Operating Lease, Liability, Payments, Due	48
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(7.8)
Operating Lease, Liability	40.2
Operating Lease, Liability, Current	10.3
Operating Lease, Liability, Noncurrent	$ 29.9

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
Fair Value (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosure [Line Items]
Transfers between Fair Value Hierarchies				$ 0	$ 0
Allowance for Credit Loss			$ 0	(0.5)	0
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down				412.4
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss			0	0	0
Available-for-sale securities, maturities of less than a year				4.9
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss			0	(0.5)	$ 0
Available-for-sale securities, maturities of less than a year				$ 4.3
Columbia Of Massachusetts
Fair Value Disclosure [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down	$ 84.4	$ 280.2
Goodwill, Impairment Loss			204.8
Impairment of Intangible Assets, Finite-lived			$ 209.7

Fair Value (Fair Value Of Finan

Fair Value (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	$ 13.2	$ 4.4
Available-for-sale securities	170.9	154.2
Total	184.1	158.6
Risk management liabilities	222.8	146.6
Total	222.8	146.6
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	0	0
Available-for-sale securities	0	0
Total	0	0
Risk management liabilities	0	0
Total	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	13.2	4.4
Available-for-sale securities	170.9	154.2
Total	184.1	158.6
Risk management liabilities	222.8	146.6
Total	222.8	146.6
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	0	0
Available-for-sale securities	0	0
Total	0	0
Risk management liabilities	0	0
Total	$ 0	$ 0

Fair Value (Available-For-Sale

Fair Value (Available-For-Sale Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosure [Line Items]
Amortized Cost	$ 163.9	$ 150.1
Gross Unrealized Gains	8	4.3
Gross Unrealized Losses	0.5	0.2
Allowance for Credit Loss	(0.5)	0
Fair Value	170.9	154.2
Debt Securities, Available-for-sale, Unrealized Loss Position	0	17.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	13.2	12.2
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	33.7	31.4
Gross Unrealized Gains	0.3	0.1
Gross Unrealized Losses	0	0.1
Allowance for Credit Loss	0	0
Fair Value	34	31.4
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	130.2	118.7
Gross Unrealized Gains	7.7	4.2
Gross Unrealized Losses	0.5	0.1
Allowance for Credit Loss	(0.5)	0
Fair Value	$ 136.9	$ 122.8

Fair Value (Carrying Amount And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Long-term debt (including current portion), Carrying Amount	$ 9,243.1	$ 7,869.6
Long-term debt (including current portion), Estimated Fair Value	$ 11,034.2	$ 8,764.4

Transfers Of Financial Assets_2

Transfers Of Financial Assets (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Number of Agreements	3
Cash from financing activities	$ 353.2	$ 46
Securitization transaction fees	2.6	$ 2.6	$ 2.6
Accounts Receivable Program
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Seasonal Limit	$ 380

Transfers Of Financial Assets_3

Transfers Of Financial Assets (Schedule Of Gross And Net Receivables Transferred As Well As Short-Term Borrowings Related To The Securitization Transactions) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Transfers and Servicing [Abstract]
Gross Receivables interest	$ 607.7	$ 569.1
Less: Receivables not transferred	607.7	215.9
Net receivables transferred	0	353.2
Accounts receivable securitization agreements outstanding	$ 0	$ 353.2

Other Commitments And Conting_3

Other Commitments And Contingencies (Narrative) (Details)	3 Months Ended		4 Months Ended	12 Months Ended		16 Months Ended	28 Months Ended
Other Commitments And Contingencies (Narrative) (Details)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2020USD ($)RateMW	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2020USD ($)RateMW	Jul. 26, 2019USD ($)
Other Commitments And Contingencies [Line Items]
Payments made in connection with operating leases					$ 49,100,000
Wind power purchase agreement capacity \| MW				500			500
Major Rail Operators				3			3
Line of Credit Facility, Amount Outstanding				$ 0		$ 0	$ 0
Proposed Class Action Settlement								$ 143,000,000
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements				(5,000,000)		1,041,000,000	1,036,000,000
Liability Insurance for Damages				800,000,000			800,000,000
Proceeds From Insurance Settlement	$ 297,000,000	$ 108,000,000					800,000,000
Recorded reserves to cover environmental remediation at various sites				$ 92,600,000		104,400,000	$ 92,600,000
Coal-fired Generating Capacity \| MW				2,080			2,080
Coal-fired Generating Capacity, Percent of Total Capacity \| Rate				72.00%
Coal-fired Generating Capacity, Percent of Total Coal-Fired Capacity \| Rate				100.00%
Wind Power Purchase Agreement, Purchase Percentage \| Rate				100.00%			100.00%
Nameplate Capacity \| MW				102			102
Expenses Other Than Third Party Claims				$ 22,000,000		420,000,000	$ 442,000,000
Costs Resulting from the Greater Lawrence Incident			$ 1,023,000,000	17,000,000		1,461,000,000	1,478,000,000
Guaranty Liabilities				40,700,000			40,700,000
Liability Associated with Schahfer Generating Station Retirement				4,600,000			4,600,000
Restructuring and Related Cost, Expected Cost				$ 38,000,000			$ 38,000,000
MGP Sites
Other Commitments And Contingencies [Line Items]
Number of waste disposal sites identified by program				54			54
Liability for estimated remediation costs				$ 85,000,000		102,200,000	$ 85,000,000
Reasonably possible remediation costs variance from reserve				$ 20,000,000			20,000,000
Columbia Of Massachusetts
Other Commitments And Contingencies [Line Items]
Gas Meters Affected				7,500
Businesses Impacted by Incident				700
Pipeline Replacement Expenses							258,000,000
Deferred Tax Assets, Net				$ 50,000,000			50,000,000
Plea Agreement Criminal Fine				$ 53,030,116
Maximum \| Columbia Of Massachusetts
Other Commitments And Contingencies [Line Items]
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements							1,050,000,000
Expenses Other Than Third Party Claims							450,000,000
Minimum \| Columbia Of Massachusetts
Other Commitments And Contingencies [Line Items]
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements							1,036,000,000
Expenses Other Than Third Party Claims							445,000,000
Coal Transportation \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year				2021
Pipeline Service Agreements [Member] \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year				2038
Pipeline Service Agreements [Member] \| Minimum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year				2021
IT Service Agreements [Member] \| Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year				2025
Standby Letters of Credit
Other Commitments And Contingencies [Line Items]
Line of Credit Facility, Amount Outstanding				$ 15,200,000		$ 10,200,000	$ 15,200,000

Other Commitments and Conting_4

Other Commitments and Contingencies (Contractual Obligation, Fiscal Year Maturity Schedule) (Details) - USD ($) $ in Millions	Feb. 09, 2021	Feb. 01, 2021	Dec. 31, 2020	Dec. 31, 2019
Long-term Purchase Commitment [Line Items]
Long-term Debt, Future Minimum Payments Due			$ 9,135
Long-term Debt, Future Minimum Payments Due, Next Twelve Months			0
Long-term Debt, Future Minimum Payments, Due in Two Years			30
Long-term Debt, Future Minimum Payments, Due in Three Years			0
Long-term Debt, Future Minimum Payments, Due in Four Years			0
Long-term Debt, Future Minimum Payments, Due in Five Years			1,260
Long-term Debt, Future Minimum Payments, Due Thereafter			7,845
Interest Payments on Long-term Debt, Future Minimum Payments Due			6,046.3
Interest Payments on Long-term Debt, Future Minimum Payments Due, Next Twelve Months			336.3
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Two Years			335.7
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Three Years			334.1
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Four Years			334.1
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Five Years			334.1
Interest Payments on Long-term Debt, Future Minimum Payments, Due Thereafter			4,372
Finance Leases, Future Minimum Payments Due			264.7
Finance Leases, Future Minimum Payments Due, Next Twelve Months			32.7
Finance Leases, Future Minimum Payments Due in Two Years			32.2
Finance Leases, Future Minimum Payments Due in Three Years			28.8
Finance Leases, Future Minimum Payments Due in Four Years			20.8
Finance Leases, Future Minimum Payments Due in Five Years			16.1
Finance Leases, Future Minimum Payments Due Thereafter			134.1
Operating Leases, Future Minimum Payments Due			48
Operating Leases, Future Minimum Payments Due, Next Twelve Months			11.7
Operating Leases, Future Minimum Payments, Due in Two Years			5.2
Operating Leases, Future Minimum Payments, Due in Three Years			4.7
Operating Leases, Future Minimum Payments, Due in Four Years			4.5
Operating Leases, Future Minimum Payments, Due in Five Years			3.7
Operating Leases, Future Minimum Payments, Due Thereafter			18.2
Energy Commodity Contracts, Future Minimum Payments Due			42.1
Energy Commodity Contracts, Future Minimum Payments Due, Next Twelve Months			42.1
Energy Commodity Contracts, Future Minimum Payments, Due in Two Years			0
Energy Commodity Contracts, Future Minimum Payments, Due in Three Years			0
Energy Commodity Contracts, Future Minimum Payments, Due in Four Years			0
Energy Commodity Contracts, Future Minimum Payments, Due in Five Years			0
Energy Commodity Contracts, Future Minimum Payments, Due Thereafter			0
Service Obligations, Pipeline Service Obligations, Future Minimum Payments Due			1,495.6
Service Obligations, Pipeline Service Obligations, Future Minimum Payments Due, Next Twelve Months			468.7
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Two Years			422.5
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Three Years			256
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Four Years			150.5
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Five Years			56.2
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due Thereafter			141.7
Service Obligations, IT Service Obligations, Future Minimum Payments Due			240.3
Service Obligations, IT Service Obligations, Future Minimum Payments Due, Next Twelve Months			74.9
Service Obligations, IT Service Obligations, Future Minimum Payments, Due in Two Years			74
Service Obligations, IT Service Obligations, Future Minimum Payments, Due in Three Years			38.1
Service Obligations, IT Service Obligations, Future Minimum Payments, Due in Four Years			30.5
Service Obligations, IT Service Obligations, Future Minimum Payments, Due in Five Years			22.8
Service Obligations, IT Service Obligations, Future Minimum Payments, Due Thereafter			0
Service Obligations, Other Service Obligations, Future Minimum Payments Due			12.6
Service Obligations, Other Service Obligations, Future Minimum Payments Due, Next Twelve Months			12.6
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Two Years			0
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Three Years			0
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Four Years			0
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Five Years			0
Service Obligations, Other Service Obligations, Future Minimum Payments, Due Thereafter			0
Other Liabilities, Future Minimum Payments Due			116.9
Other Liabilities, Future Minimum Payments Due, Next Twelve Months			26
Other Liabilities, Future Minimum Payments, Due in Two Years			0.8
Other Liabilities, Future Minimum Payments, Due in Three Years			90.1
Other Liabilities, Future Minimum Payments, Due in Four Years			0
Other Liabilities, Future Minimum Payments, Due in Five Years			0
Other Liabilities, Future Minimum Payments, Due Thereafter			0
Total Future Minimum Lease Payments Due			17,401.5
Total Future Minimum Lease Payments Due, Next Twelve Months			1,005
Total Future Minimum Lease Payments, Due in Two Years			900.4
Total Future Minimum Lease Payments, Due in Three Years			751.8
Total Future Minimum Lease Payments, Due in Four Years			540.4
Total Future Minimum Lease Payments, Due in Five Years			1,692.9
Total Future Minimum Lease Payments, Due Thereafter			12,511
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net			(86.9)	$ (70.5)
Finance Leases, Future Minimum Payments, Interest Included in Payments			69.7
Operating Leases, Future Minimum Payaments, Interest Included in Payments			7.8
Subsequent Event
Long-term Purchase Commitment [Line Items]
Service Obligations, Pipeline Service Obligations, Future Minimum Payments Due		$ 638.6
Service Obligations, Other Service Obligations, Future Minimum Payments Due	$ 12.1
Fleet Lease
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months			30
Operating Leases, Future Minimum Payments, Due in Two Years			27.7
Operating Leases, Future Minimum Payments, Due in Three Years			24.9
Operating Leases, Future Minimum Payments, Due in Four Years			22
Operating Leases, Future Minimum Payments, Due in Five Years			19
Operating Leases, Future Minimum Payments, Due Thereafter			$ 21.5

Other Commitments and Conting_5

Other Commitments and Contingencies (Expense Incurred and Insurance Recoveries) (Details) - USD ($) $ in Millions	4 Months Ended	12 Months Ended	16 Months Ended	28 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Expense and Insurance Recoveries [Line Items]
Third-Party Claims, fines, penalties, and settlements		$ (5)	$ 1,041	$ 1,036
Other incident-related costs		22	420	442
Total	$ 1,023	17	1,461	1,478
Insurance Recoveries		0	(800)	(800)
Impact to income (loss) before income taxes		$ 17	$ 661	$ 678

Other Commitments And Conting_6

Other Commitments And Contingencies (Estimated Incident Expenses) (Details) - USD ($) $ in Millions	12 Months Ended	16 Months Ended	28 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Estimated Incident Expenses [Line Items]
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements	$ (5)	$ 1,041	$ 1,036
Expenses Other Than Third Party Claims	$ 22	$ 420	442
Maximum \| Columbia Of Massachusetts
Estimated Incident Expenses [Line Items]
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements			1,050
Expenses Other Than Third Party Claims			450
Minimum \| Columbia Of Massachusetts
Estimated Incident Expenses [Line Items]
Expenses Related to Third-Party Claims, Fines, Penalties, and settlements			1,036
Expenses Other Than Third Party Claims			$ 445

Other Commitments And Conting_7

Other Commitments And Contingencies (Restructuring) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 11.1	$ 0
Restructuring Reserve, Period Increase (Decrease)	33.5
Payments for Restructuring	(21.2)
Restructuring Reserve, Accrual Adjustment	$ (1.2)

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ (64.6)	$ (55.9)	$ 48.4
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.5	0.5	(32.7)
Net current-period other comprehensive income (loss)	(64.1)	(55.4)	15.7
Accumulated other comprehensive loss	(156.7)	(92.6)	(37.2)	$ (43.4)
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss			(9.5)
Gains and Losses on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	3.3	6.1	(3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(0.6)	(0.4)	0.4
Net current-period other comprehensive income (loss)	2.7	5.7	(2.6)
Accumulated other comprehensive loss	6	3.3	(2.4)	0.2
Gains and Losses on Securities \| Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss			0
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(70.8)	(64.3)	55.8
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.1	0.1	(33.1)
Net current-period other comprehensive income (loss)	(70.7)	(64.2)	22.7
Accumulated other comprehensive loss	(147.9)	(77.2)	(13)	(29.4)
Gains and Losses on Cash Flow Hedges \| Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss			(6.3)
Pension and OPEB Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	2.9	2.3	(4.4)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1	0.8	0
Net current-period other comprehensive income (loss)	3.9	3.1	(4.4)
Accumulated other comprehensive loss	$ (14.8)	$ (18.7)	(21.8)	$ (14.2)
Pension and OPEB Items \| Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss			$ (3.2)

Other, Net (Schedule Of Other N

Other, Net (Schedule Of Other Net) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Nonoperating Income (Expense) [Abstract]
Charitable Contributions, Greater Lawrence Incident				$ 20.7
Interest income		$ 5.5	$ 7.7	6.6
AFUDC equity		9.9	8	14.2
Charitable Contributions	$ 20	(1.5)	(5.1)	(45.3)
Pension and Other Postretirement Non Service Cost		9.3	(16.5)	18
Sale of emission reduction credits		4.6	0	0
Interest rate swap settlement gain			0	46.2
Miscellaneous		4.3	0.7	3.8
Total Other, net		$ 32.1	$ (5.2)	$ 43.5

Interest Expense, Net (Details)

Interest Expense, Net (Details) - USD ($) $ in Millions	12 Months Ended
Interest Expense, Net (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Expense [Abstract]
Interest on long-term debt	$ 354.2	$ 327.7	$ 342.2
Interest on short-term borrowings	14.7	50.8	31.8
Debt discount/cost amortization	9.1	8.3	7.7
Accounts receivable securitization fees	2.6	2.6	2.6
Allowance for borrowed funds used and interest capitalized during construction	(7)	(7.5)	(9.1)
Debt-based post-in-service carrying charges	(14.6)	(18.7)	(35)
Other	11.7	15.7	13.1
Total Interest Expense, net	$ 370.7	$ 378.9	$ 353.3

Segments Of Business (Narrative

Segments Of Business (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
Segments Of Business (Narrative) (Details) $ in Millions	Dec. 31, 2019USD ($)	Dec. 31, 2020
Goodwill [Line Items]
Number of Reportable Segments		2
Number of counties in which electric service provided by Electric Operations		20
Columbia Of Massachusetts
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 204.8

Segments Of Business (Schedule

Segments Of Business (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating Revenues									$ 4,681.7	$ 5,208.9	$ 5,114.5
Operating Income (Loss)	$ 218.1	$ 92.8	$ 91.7	$ 148.2	$ (38)	$ 91	$ 463.5	$ 374.2	550.8	890.7	124.7
Consolidated Depreciation and Amortization									725.9	717.4	599.6
Consolidated Assets	22,040.5				22,659.8				22,040.5	22,659.8	21,804
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments									1,720.8	1,867.8	1,814.6
Gas Distribution Operations
Segment Reporting Information [Line Items]
Operating Revenues									3,128.1	3,509.7	3,406.4
Intersegment									3,140.2	3,522.8	3,419.5
Operating Income (Loss)									199.1	675.4	(254.1)
Consolidated Depreciation and Amortization									363.1	403.2	301
Consolidated Assets	13,433				14,224.5				13,433	14,224.5	13,527
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments									1,266.9	1,380.3	1,315.3
Electric Operations
Segment Reporting Information [Line Items]
Operating Revenues									1,535.9	1,698.4	1,707.4
Intersegment									1,536.6	1,699.2	1,708.2
Operating Income (Loss)									348.8	406.8	386.1
Consolidated Depreciation and Amortization									321.3	277.3	262.9
Consolidated Assets	6,443.1				6,027.6				6,443.1	6,027.6	5,735.2
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments									422.8	468.9	499.3
Corporate and Other
Segment Reporting Information [Line Items]
Operating Revenues									17.7	0.8	0.7
Intersegment									467.5	468.9	518.3
Operating Income (Loss)									2.9	(191.5)	(7.3)
Consolidated Depreciation and Amortization									41.5	36.9	35.7
Consolidated Assets	$ 2,164.4				$ 2,407.7				2,164.4	2,407.7	2,541.8
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments									31.1	18.6	0
Unaffiliated \| Gas Distribution Operations
Segment Reporting Information [Line Items]
Operating Revenues									3,128.1	3,509.7	3,406.4
Unaffiliated \| Electric Operations
Segment Reporting Information [Line Items]
Operating Revenues									1,535.9	1,698.4	1,707.4
Unaffiliated \| Corporate and Other
Segment Reporting Information [Line Items]
Operating Revenues									17.7	0.8	0.7
Intersegment \| Gas Distribution Operations
Segment Reporting Information [Line Items]
Intersegment									12.1	13.1	13.1
Intersegment \| Electric Operations
Segment Reporting Information [Line Items]
Intersegment									0.7	0.8	0.8
Intersegment \| Corporate and Other
Segment Reporting Information [Line Items]
Intersegment									449.8	468.1	517.6
Eliminations
Segment Reporting Information [Line Items]
Intersegment									$ (462.6)	$ (482)	$ (531.5)

Quarterly Financial Data (Narra

Quarterly Financial Data (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended						12 Months Ended			28 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Quarterly Financial Data [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down							$ 412.4
Proceeds From Insurance Settlement					$ 297	$ 108				$ 800
Loss on early extinguishment of long-term debt	$ 243.4						$ (243.5)	$ 0	$ (45.5)
Columbia Of Massachusetts
Quarterly Financial Data [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		$ 84.4	$ 280.2
Goodwill, Impairment Loss				$ 204.8
Impairment of Intangible Assets, Finite-lived				$ 209.7

Quarterly Financial Data (Sched

Quarterly Financial Data (Schedule Of Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Operating Revenues	$ 1,211	$ 902.5	$ 962.7	$ 1,605.5	$ 1,397.2	$ 931.5	$ 1,010.4	$ 1,869.8
Operating Income (Loss)	218.1	92.8	91.7	148.2	(38)	91	463.5	374.2	$ 550.8	$ 890.7	$ 124.7
Net Income (Loss)	87.8	(172.9)	(4.7)	75.6					(14.2)	383.1	(50.6)
Net Income (Loss) Attributable to Noncontrolling Interest	3.4	0	0	0					3.4	0	0
Net Income (Loss) Attributable to NiSource	84.4	(172.9)	(4.7)	75.6	(139.3)	6.6	296.9	218.9	(17.6)	383.1	(50.6)
Preferred Dividends	(13.7)	(13.8)	(13.8)	(13.8)	(13.7)	(13.8)	(13.8)	(13.8)	(55.1)	(55.1)	(15)
Net Income (Loss) Available to Common Stockholders	$ 70.7	$ (186.7)	$ (18.5)	$ 61.8	$ (153)	$ (7.2)	$ 283.1	$ 205.1	$ (72.7)	$ 328	$ (65.6)
Basic Earnings (Loss) Per Share	$ 0.18	$ (0.49)	$ (0.05)	$ 0.16	$ (0.41)	$ (0.02)	$ 0.76	$ 0.55	$ (0.19)	$ 0.88	$ (0.18)
Diluted Earnings (Loss) Per Share	$ 0.18	$ (0.49)	$ (0.05)	$ 0.16	$ (0.41)	$ (0.02)	$ 0.75	$ 0.55	$ (0.19)	$ 0.87	$ (0.18)

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Non-cash transactions:
Capital expenditures included in current liabilities	$ 170.4	$ 223.6	$ 152
Assets acquired under a finance lease		26.4	54.6
Assets acquired under an operating lease		13.4	0
Reclassification of other property to regulatory assets	0	0	245.3
Assets recorded for asset retirement obligations	91.5	54.6	78.1
Obligation to the Developer	69.7	0	0
Schedule of interest and income taxes paid:
Cash paid for interest, net of interest capitalized amounts	349	349.7	354.2
Cash paid for income taxes, net of refunds(4)	$ (1)	$ 10.8	$ 3.3

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reserve For Accounts Receivable [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 19.2	$ 21.1	$ 18.3
Valuation Allowances and Reserves, Charged to Cost and Expense	31.6	21.6	20.2
Valuation Allowances and Reserves, Charged to Other Accounts	33	41.3	43.7
Deductions for Purposes for which Reserves were Created	31.5	64.8	61.1
Ending Balance	52.3	19.2	21.1
Reserve For Other Investments [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	3	3	3
Valuation Allowances and Reserves, Charged to Cost and Expense	0	0	0
Valuation Allowances and Reserves, Charged to Other Accounts	0	0	0
Deductions for Purposes for which Reserves were Created	3	0	0
Ending Balance	$ 0	$ 3	$ 3