Investments (Selected Information Regarding Equity and Fixed Income Securities) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		$ 2,966	$ 3,282	$ 3,985
Realized gains	[1]	92	143	441
Realized losses	[1]	169	296	91
Virginia Electric and Power Company
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		1,876	1,538	1,791
Realized gains	[1]	50	48	228
Realized losses	[1]	$ 99	$ 107	$ 35

[1] Includes realized gains and losses recorded to the nuclear decommissioning trust regulatory liability as discussed in Note 2.