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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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Regulated Operations [Line Items] |  |
Regulatory Liabilities | $ 1,581.7 | $ 1,789.3
Regulatory Liability, Current | 150.5 | 278.6
Regulatory Liability, Noncurrent | 1,431.2 | 1,510.7
Deferred Derivative Gain (Loss) |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 28.7 | 23.3
Customer Assistance Programs |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 9.4 | 19.8
Rate Refunds |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 16.6 | 16.1
Off-Systems sales sharing |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 21.4 | 19.0
HLBV Adjustments under ASC 980 |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 77.0 | 18.1
Overrecovered Gas And Fuel Costs |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 21.4 | 144.5
Cost Of Removal |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 482.8 | 597.2
Regulatory Effects Of Accounting For Income Taxes |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 827.0 | 849.9
Other Postretirement Costs |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 40.4 | 54.0
Other Liabilities |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | $ 57.0 | $ 47.4

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- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + Details
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