Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenues From Contract With Customer [Line Items]
Revenue recognized from contract liability balances	$ 48	$ 42
Other Current Liabilities and Other Deferred Credits and Other Liabilities
Revenues From Contract With Customer [Line Items]
Contract liability balances	47	51
Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue recognized from contract liability balances	39	33
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	$ 40	$ 39