Components of Accumulated Other Comprehensive Loss, Net - EEGH (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 46,977	$ 32,578
Other comprehensive income (loss)	112	(547)
Balance	47,051	32,572
Eastern Energy Gas Holdings, LLC [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	6,995	10,229
Other comprehensive income (loss)	12	(84)
Balance	7,078	10,078
Accumulated Other Comprehensive Loss [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss)	112	(547)
Accumulated Other Comprehensive Loss [Member] | Eastern Energy Gas Holdings, LLC [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(53)	(187)
Other comprehensive income (loss)	8	(84)
Balance	(45)	(271)
Unrecognized Amounts On Retirement Benefits [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss)	(7)	(34)
Unrecognized Amounts On Retirement Benefits [Member] | Eastern Energy Gas Holdings, LLC [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(12)	(106)
Other comprehensive income (loss)	2	1
Balance	(10)	(105)
Unrealized Gains (Losses) On Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss)	14	(33)
Unrealized Gains (Losses) On Cash Flow Hedges [Member] | Eastern Energy Gas Holdings, LLC [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(51)	(81)
Other comprehensive income (loss)	10	(85)
Balance	(41)	(166)
AOCI Attributable to Noncontrolling Interest [Member] | Eastern Energy Gas Holdings, LLC [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	10	0
Other comprehensive income (loss)	(4)	0
Balance	$ 6	$ 0