Income Taxes (Income Tax Expense for Continuing Operations Including Noncontrolling Interests) (Detail) - USD ($) $ in Millions		12 Months Ended
	Nov. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal		$ (314)	$ (94)	$ 294
State		(81)	58	82
Total current expense (benefit)		(395)	(36)	376
Deferred:
Taxes before operating loss carryforwards, investment tax credits and tax reform		12	168	30
2017 Tax Reform Act		0	0	46
Tax utilization expense of operating loss carryforwards		44	119	92
Investment tax credits		311	(51)	(56)
State		72	(50)	34
Total deferred expense (benefit)		439	186	146
Investment tax credit-gross deferral		42	62	2
Investment tax credit-amortization		(3)	(3)	(2)
Total income tax expense	$ 336	83	209	522
Virginia Electric and Power Company
Current:
Federal		364	286	36
State		71	58	40
Total current expense (benefit)		435	344	76
Deferred:
Taxes before operating loss carryforwards, investment tax credits and tax reform		(226)	(128)	199
2017 Tax Reform Act		0	0	21
Tax utilization expense of operating loss carryforwards		0	0	0
Investment tax credits		(27)	(34)	(51)
State		7	22	55
Total deferred expense (benefit)		(246)	(140)	224
Investment tax credit-gross deferral		42	62	2
Investment tax credit-amortization		(2)	(2)	(2)
Total income tax expense		$ 229	$ 264	$ 300