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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
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

Regulated Operations [Line Items]

+ References

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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

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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.

+ 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

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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