Risk Management and Hedging Activities - EEGH - Gain (Loss) Recorded In Income (Details) - Not Designated as Hedging Instrument [Member] - Eastern Energy Gas Holdings, LLC [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 4	$ 0	$ (11)
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	5	0	0
Commodity Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (1)	$ 0	$ (11)