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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulated Operations [Line Items]
Regulatory Liabilities	$ 1,789.3	$ 2,012.6
Regulatory Liability, Current	278.6	236.8
Regulatory Liability, Noncurrent	$ 1,510.7	1,775.8
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	69 years
Deferred Derivative Gain (Loss)
Regulated Operations [Line Items]
Regulatory Liabilities	$ 23.3	90.0
Customer Assistance Programs
Regulated Operations [Line Items]
Regulatory Liabilities	19.8	32.9
Rate Refunds
Regulated Operations [Line Items]
Regulatory Liabilities	16.1	51.4
Off-Systems sales sharing
Regulated Operations [Line Items]
Regulatory Liabilities	19.0	12.3
HLBV Adjustments under ASC 980
Regulated Operations [Line Items]
Regulatory Liabilities	18.1	5.4
Overrecovered Gas And Fuel Costs
Regulated Operations [Line Items]
Regulatory Liabilities	144.5	20.6
Cost Of Removal
Regulated Operations [Line Items]
Regulatory Liabilities	597.2	675.9
Regulatory Effects Of Accounting For Income Taxes
Regulated Operations [Line Items]
Regulatory Liabilities	849.9	996.3
Other Postretirement Costs
Regulated Operations [Line Items]
Regulatory Liabilities	54.0	66.8
Other Liabilities
Regulated Operations [Line Items]
Regulatory Liabilities	$ 47.4	$ 61.0

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Regulated Operations [Line Items]

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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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-Topic 980
-SubTopic 405
-Name Accounting Standards Codification
-Section 25
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-URI https://asc.fasb.org//1943274/2147481854/980-405-25-1

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

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-Topic 980
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-Section 25
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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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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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