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v3.20.1

Other Commitments And Contingencies (Narrative) (Details) |  | 3 Months Ended | 4 Months Ended | 16 Months Ended | 19 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 31, 2019 MW | Mar. 31, 2020 USD ($) Rate MW | Dec. 31, 2018 USD ($) | Dec. 31, 2019 USD ($) | Mar. 31, 2020 USD ($) MW | Jul. 26, 2019 USD ($) | Jan. 01, 2019 Rate MW
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Guaranty Liabilities |  | $ 8,500,000 |  |  | $ 8,500,000 |  |
Gas Meters moved from inside to outside | 2,200 |  |  |  |  |  |
Litigation Settlement, Amount Awarded to Other Party |  |  |  |  |  | $ 143,000,000 |
Expenses Related to Third-Party Claims |  | 0 |  | $ 1,041,000,000 | 1,041,000,000 |  |
Liability Insurance for Damages |  | 800,000,000 |  |  | 800,000,000 |  |
Proceeds From Insurance Settlement |  |  |  |  | 800,000,000 |  |
Recorded reserves to cover environmental remediation at various sites |  | $ 91,400,000 |  | 104,400,000 | $ 91,400,000 |  |
Coal-fired Generating Capacity | MW |  | 2,080 |  |  |  |  |
Coal-fired Generating Capacity, Percent of Total Capacity | Rate |  | 72.00% |  |  |  |  |
Coal-fired Generating Capacity, Percent of Total Coal-Fired Capacity | Rate |  | 100.00% |  |  |  |  |
Wind Power Purchase Agreement, Purchase Percentage | Rate |  |  |  |  |  |  | 100.00%
Planned Replacement Capacity | MW |  | 1,600 |  |  | 1,600 |  |
Other incident-related costs |  | $ 9,000,000 |  | 420,000,000 | $ 429,000,000 |  |
Costs Resulting from the Greater Lawrence Incident |  | $ 9,000,000 | $ 1,023,000,000 | 1,461,000,000 | $ 1,470,000,000 |  |
MGP Sites |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Number of waste disposal sites identified by program |  | 63 |  |  | 63 |  |
Liability for Estimated Remediation Costs |  | $ 86,800,000 |  | 102,200,000 | $ 86,800,000 |  |
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 |  |  |  |  |
Miles of Affected Cast Iron and Bare Steel Pipeline System |  | 45 |  |  |  |  |
Pipeline Replacement Expenses |  |  |  |  | 258,000,000 |  |
Deferred Tax Assets, Net |  | $ 50,000,000 |  |  | 50,000,000 |  |
NIPSCO |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Estimated Cost of Compliance with Effluent Limitations Guidelines |  | 170,000,000 |  |  |  |  |
Maximum | Columbia Of Massachusetts |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Civil Penalty Assessed for Violation of Federal Pipeline Safety Regulations |  | 218,647 |  |  |  |  |
Civil Penalty Assessed for Series of Violations of Federal Pipeline Safety Regulations |  | 2,200,000 |  |  |  |  |
Penalty Per Violation of Emergency Response Plan |  | 250,000 |  |  |  |  |
Penalty for Violations of Emergency Response Plan |  | 20,000,000.0 |  |  |  |  |
Penalty Per Violation of Operational Directives During Restoration Efforts |  | 1,000,000.0 |  |  |  |  |
Expenses Related to Third-Party Claims |  |  |  |  | 1,055,000,000 |  |
Other incident-related costs |  |  |  |  | 460,000,000 |  |
Minimum | Columbia Of Massachusetts |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Expenses Related to Third-Party Claims |  |  |  |  | 1,041,000,000 |  |
Other incident-related costs |  |  |  |  | 450,000,000 |  |
Standby Letters of Credit |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Long-term Line of Credit |  | $ 10,200,000 |  | $ 10,200,000 | $ 10,200,000 |  |
Build Transfer Agreement [Member] |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Nameplate Capacity | MW | 300 |  |  |  |  |  | 100
Purchase Power Agreements - Jan 2019 [Member] |  |  |  |  |  |  |
Other Commitments And Contingencies [Line Items] |  |  |  |  |  |  |
Long-term Purchase Commitment, Period |  | 20 years |  |  |  |  |

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