Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
Oct. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Regulatory Assets and Liabilities Disclosure [Line Items]
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		$ 1,324.7	$ 1,207.0
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		50 years
Columbia of Maryland COVID Relief Funds		$ 0.8
COVID-19 related regulatory asset		2,580.8	2,492.2
Regulatory Liabilities		2,012.6	1,980.0
Overrecovered Gas And Fuel Costs
Regulatory Assets and Liabilities Disclosure [Line Items]
Regulatory Liabilities		20.6	$ 5.4
Columbia Of Ohio
Regulatory Assets and Liabilities Disclosure [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 68.2	$ 221.4
Public Utilities, Requested Rate Increase (Decrease), Percentage	7.97%	21.30%
NIPSCO - Electric \| Overrecovered Gas And Fuel Costs
Regulatory Assets and Liabilities Disclosure [Line Items]
Regulatory Liabilities		$ 8.0

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Regulatory Assets and Liabilities Disclosure

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested rate increase (decrease) with regulatory agency.

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

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Remaining balance of regulatory assets for which no return on investment during recovery is provided. In some cases, a regulator may permit an enterprise to include a cost that would be charged to expense by an unregulated enterprise as an allowable cost over a period of time by amortizing that cost for rate-making purposes, but the regulator does not include the unrecovered amount in the rate base.

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Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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