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Litigation and Environmental - Federal Energy Regulatory Commission Proceedings (Details) - Federal Energy Regulatory Commission - Unfavorable Regulatory Action - Pending Litigation
$ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
claims
SFPP | Rate Refunds, and Reductions Not Resolved in East Line Settlement  
Loss Contingencies [Line Items]  
Loss Contingency, Damages Sought, Value | $ $ 50
EPNG  
Loss Contingencies [Line Items]  
Loss Contingency, Pending Claims, Number | claims 2
Reparations, Refunds and Rate Reductions | SFPP  
Loss Contingencies [Line Items]  
Loss Contingency Period of Time Litigation Concerns 2 years