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Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Regulated Operations [Line Items] |  |
Regulatory Liabilities | $ 1,980.0 | $ 2,065.5
Regulatory Liability, Current | 137.4 | 161.3
Regulatory Liability, Noncurrent | 1,842.6 | 1,904.2
Deferred Derivative Gain (Loss) |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 34.2 | 14.0
Overrecovered Gas And Fuel Costs |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 5.4 | 47.8
Cost Of Removal |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 749.5 | 775.2
Regulatory Effects Of Accounting For Income Taxes |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 1,040.8 | 1,105.1
Other Postretirement Costs |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | 75.9 | 69.5
Other Liabilities |  |
Regulated Operations [Line Items] |  |
Regulatory Liabilities | $ 74.2 | $ 53.9

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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- Definition 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 -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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- Definition 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 -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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