Components of Accumulated Other Comprehensive Loss, Net - EEGH - Reclassifications from AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Loss, Net [Line Items]
Interest expense		$ 2,021	$ 1,912	$ 1,838
Other, net		88	97	(9)
Income tax expense (benefit)		308	(598)	(583)
Net income		7,014	2,968	2,591
Eastern Energy Gas Holdings, LLC [Member]
Accumulated Other Comprehensive Loss, Net [Line Items]
Interest expense		333	311	174
Other, net		42	43	48
Net income from continuing operations		273	701	632
Income tax expense (benefit)		(24)	101	124
Net income from discontinued operations	[1]	0	141	24
Net income		273	842	656
Eastern Energy Gas Holdings, LLC [Member] | Cash Flow Hedge [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Net income from continuing operations		132	7	26
Income tax expense (benefit)		(34)	(2)	(7)
Net income		98	5	19
Eastern Energy Gas Holdings, LLC [Member] | Cash Flow Hedge [Member] | Interest Rate Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Interest expense		157	5	5
Eastern Energy Gas Holdings, LLC [Member] | Cash Flow Hedge [Member] | Foreign Exchange Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Other, net		(25)	6	13
Eastern Energy Gas Holdings, LLC [Member] | Cash Flow Hedge [Member] | Commodity Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Net income from discontinued operations			(4)	8
Eastern Energy Gas Holdings, LLC [Member] | Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Net income from continuing operations		6	7	6
Income tax expense (benefit)		(2)	(2)	(2)
Net income		4	5	4
Eastern Energy Gas Holdings, LLC [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss, Net [Line Items]
Other, net		$ 6	$ 7	$ 6

[1] Includes income tax expense of $33 million and less than $1 million for the years ended December 31, 2019 and 2018, respectively.