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Other Commitments And Contingencies (Narrative) (Details) $ in Millions | 12 Months Ended | 28 Months Ended |
--- | --- | --- | ---
Dec. 31, 2022 USD ($) Rate MW | Dec. 31, 2020 USD ($) | Dec. 31, 2021 USD ($)
Other Commitments And Contingencies [Line Items] |  |  |
Wind power purchase agreement capacity | MW | 500 |  |
Major Rail Operators | 3 |  |
Line of Credit Facility, Amount Outstanding | $ 0.0 |  | $ 0.0
Guarantor Obligations, Current Carrying Value | $ 841.6 |  | 288.9
Wind Power Purchase Agreement, Purchase Percentage | Rate | 100.00% |  |
Restructuring and Related Cost, Expected Cost | $ 38.0 |  |
Estimated Maximum Disgorgement Exposure | 9.7 |  |
Proceeds from Legal Settlements | 105.0 |  |
Accrual for Environmental Loss Contingencies, Gross | $ 86.5 |  | 91.1
MGP Sites |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Number of waste disposal sites identified by program | 53 |  |
Liability for estimated remediation costs | $ 81.0 |  | 85.1
Reasonably possible remediation costs variance from reserve | $ 17.0 |  |
Columbia Of Massachusetts |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Pipeline Replacement Expenses |  | $ 258.0 |
Coal Transportation | Maximum |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Long Term Purchase Commitment Expiration Year | 2028 |  |
Pipeline Service Agreements [Member] | Maximum |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Long Term Purchase Commitment Expiration Year | 2038 |  |
Pipeline Service Agreements [Member] | Minimum |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Long Term Purchase Commitment Expiration Year | 2023 |  |
IT Service Agreements [Member] | Maximum |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Long Term Purchase Commitment Expiration Year | 2028 |  |
Standby Letters of Credit |  |  |
Other Commitments And Contingencies [Line Items] |  |  |
Line of Credit Facility, Amount Outstanding | $ 10.2 |  | $ 18.9

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