Investments (Selected Information Regarding Equity and Fixed Income Securities) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		$ 651	$ 869	$ 2,230	$ 2,007
Realized gains	[1]	18	5	77	48
Realized losses	[1]	21	33	93	110
Virginia Electric and Power Company
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		297	535	1,370	1,254
Realized gains	[1]	13	4	52	29
Realized losses	[1]	$ 16	$ 16	$ 61	$ 61

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