Investments (Selected Information Regarding Equity and Fixed Income Securities) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		$ 884	$ 594	$ 1,579	$ 1,138
Realized gains	[1]	27	22	59	43
Realized losses	[1]	34	36	72	77
Virginia Electric and Power Company
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales		602	346	1,073	719
Realized gains	[1]	16	8	39	25
Realized losses	[1]	$ 22	$ 14	$ 45	$ 45

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