Investments (Selected Information Regarding Equity and Fixed Income Securities) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025		Mar. 31, 2024
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales	$ 931		$ 695
Realized gains	11	[1]	32
Realized losses	20	[1]	38
Virginia Electric and Power Company
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales	568		471
Realized gains	9		23	[1]
Realized losses	$ 15		$ 23	[1]

[1] Includes realized gains and losses recorded to the nuclear decommissioning trust regulatory liability.