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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Regulated Operations [Line Items] |  |
Total Assets | $ 2,460.2 | $ 2,580.8
Regulatory Assets, Current | 214.3 | 233.2
Regulatory Assets, Noncurrent | $ 2,245.9 | 2,347.6
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided | 69 years |
Unrecognized Pension Benefit And Other Postretirement Benefit Costs |  |
Regulated Operations [Line Items] |  |
Total Assets | $ 561.6 | 607.5
Other Postretirement Costs |  |
Regulated Operations [Line Items] |  |
Total Assets | 59.7 | 72.2
Environmental Costs |  |
Regulated Operations [Line Items] |  |
Total Assets | 40.6 | 41.4
Regulatory Effects Of Accounting For Income Taxes |  |
Regulated Operations [Line Items] |  |
Total Assets | 163.5 | 158.0
Underrecovered Gas And Fuel Costs |  |
Regulated Operations [Line Items] |  |
Total Assets | 12.7 | 85.5
Depreciation |  |
Regulated Operations [Line Items] |  |
Total Assets | 201.9 | 191.3
Post-In Service Carrying Charges |  |
Regulated Operations [Line Items] |  |
Total Assets | 269.9 | 251.5
Safety Activity Costs |  |
Regulated Operations [Line Items] |  |
Total Assets | 206.6 | 200.7
DSM Program |  |
Regulated Operations [Line Items] |  |
Total Assets | 25.0 | 37.5
Retired coal generating stations |  |
Regulated Operations [Line Items] |  |
Total Assets | 682.0 | 744.0
Deferred Derivative Gain (Loss) |  |
Regulated Operations [Line Items] |  |
Total Assets | 24.4 | 10.0
Deferred Property Taxes |  |
Regulated Operations [Line Items] |  |
Total Assets | 72.3 | 68.5
Renewable Energy Program |  |
Regulated Operations [Line Items] |  |
Total Assets | 60.8 | 37.7
Other Assets |  |
Regulated Operations [Line Items] |  |
Total Assets | $ 79.2 | $ 75.0

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481878/980-340-50-1 + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481878/980-340-50-1 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481878/980-340-50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 55 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481849/980-340-55-2 + Details
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