Litigation and Environmental Federal Energy Regulatory Commission Proceedings (Details) - Federal Energy Regulatory Commission [Member] - Unfavorable Regulatory Action [Member] - Pending Litigation [Member] $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) claims
EPNG
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number | claims	2
Reparations, Refunds and Rate Reductions [Member] | SFPP
Loss Contingencies [Line Items]
Loss Contingency Period of Time Litigation Concerns	2 years
Annual Rate Reductions [Member] | SFPP
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	$ 50
Revenue Subject to Refund [Member] | SFPP
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	$ 400