Income Taxes - EEGH - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Income Tax Expense (Benefit) [Line Items]
Current Federal Tax Expense (Benefit)	$ (1,537)	$ (956)	$ (686)
Current State and Local Tax Expense (Benefit)	(121)	(13)	(9)
Current Income Tax Expense (Benefit)	(1,572)	(888)	(591)
Deferred Federal Income Tax Expense (Benefit)	1,438	431	165
Deferred State and Local Income Tax Expense (Benefit)	424	(127)	(131)
Deferred Income Tax Expense (Benefit)	1,883	296	14
Income tax expense (benefit)	308	(598)	(583)
Eastern Energy Gas Holdings, LLC [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Current Federal Tax Expense (Benefit)	(20)	130	(227)
Current State and Local Tax Expense (Benefit)	1	17	31
Current Income Tax Expense (Benefit)	(19)	147	(196)
Deferred Federal Income Tax Expense (Benefit)	23	(36)	337
Deferred State and Local Income Tax Expense (Benefit)	(28)	(10)	(17)
Deferred Income Tax Expense (Benefit)	(5)	(46)	320
Income tax expense (benefit)	$ (24)	$ 101	$ 124