Risk Management and Hedging Activities - EEGH - Gain (Loss) Recognized In Other Comprehensive Income (Details) - Eastern Energy Gas Holdings, LLC [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		$ (92)	$ (85)	$ (21)
Amount of Gain (Loss) Reclassified from AOCI to Income	$ (141)	(132)	(7)	(26)
Commodity [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)			1	1
Amount of Gain (Loss) Reclassified from AOCI to Income			4	(8)
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		(104)	(68)	(16)
Interest Rate Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from AOCI to Income		(157)	(5)	(5)
Foreign Exchange Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		12	(18)	(6)
Foreign Exchange Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from AOCI to Income		$ 25	$ (6)	$ (13)