Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenues From Contract With Customer [Line Items]
Revenue recognized from contract liability balances	$ 43	$ 46
Other Current Liabilities and Other Deferred Credits and Other Liabilities
Revenues From Contract With Customer [Line Items]
Contract liability balances	59		$ 47
Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue recognized from contract liability balances	40	$ 39
Virginia Electric and Power Company | Other Current Liabilities and Other Deferred Credits and Other Liabilities
Revenues From Contract With Customer [Line Items]
Contract liability balances	$ 53		$ 40