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v3.21.1

Other Commitments And Contingencies (Narrative) (Details) | 3 Months Ended | 4 Months Ended | 31 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2021 USD ($) Rate | Dec. 31, 2018 USD ($) | Mar. 31, 2021 USD ($) Rate | Dec. 31, 2020 USD ($) | Jul. 26, 2019 USD ($)
Other Commitments And Contingencies [Line Items] |  |  |  |  |
Guaranty Liabilities | $ 34,000,000.0 |  | $ 34,000,000.0 |  |
Litigation Settlement, Amount Awarded to Other Party |  |  |  |  | $ 143,000,000
Recorded reserves to cover environmental remediation at various sites | $ 90,600,000 |  | $ 90,600,000 | $ 92,600,000 |
Wind Power Purchase Agreement, Purchase Percentage | Rate | 100.00% |  | 100.00% |  |
Costs Resulting from the Greater Lawrence Incident |  | $ 1,023,000,000 |  |  |
Restructuring and Related Cost, Expected Cost | $ 40,000,000 |  | $ 40,000,000 |  |
Restructuring and Related Cost, Cost Incurred to Date | $ 38,100,000 |  | $ 38,100,000 |  |
MGP Sites |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |
Number of waste disposal sites identified by program | 54 |  | 54 |  |
Liability for Estimated Remediation Costs | $ 84,300,000 |  | $ 84,300,000 | 85,000,000.0 |
Reasonably possible remediation costs variance from reserve | $ 20,000,000 |  | 20,000,000 |  |
Columbia Of Massachusetts |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |
Gas Meters Affected | 7,500 |  |  |  |
Businesses Impacted by Incident | 700 |  |  |  |
Plea Agreement Criminal Fine | $ 53,030,116 |  |  |  |
Pipeline Replacement Expenses |  |  | 258,000,000 |  |
Deferred Tax Assets, Net | 50,000,000 |  | 50,000,000 |  |
Minimum | Columbia Of Massachusetts |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |
Expenses Related to Third-Party Claims |  |  | 1,040,000,000 |  |
Standby Letters of Credit |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |
Long-term Line of Credit | $ 15,200,000 |  | $ 15,200,000 | $ 15,200,000 |

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