Investments (Selected Information Regarding Equity and Fixed Income Securities) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		$ 695	$ 544
Realized gains	[1]	32	21
Realized losses	[1]	38	41
Virginia Electric and Power Company
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		471	373
Realized gains	[1]	23	17
Realized losses	[1]	$ 23	$ 31

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