Quarterly Financial Data (Unaudited) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023
Quarterly Financial Information Disclosure [Abstract]
Losses from lower market returns on pension and other postretirement plan assets after tax			$ 238
Gain (loss) on investments, after tax		$ 132	$ 202
Investment, Type [Extensible Enumeration]		Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]
Gain (loss) related to mark-to-market impact economic hedging activities after tax	$ (93)	$ 103
Expected to be recovered from customers charge after tax	$ 77
Gain on sale of Dominion Energy's noncontrolling interest in cove point					$ 348
Charges reflecting the recognition of deferred taxes					$ 939
Impairment charge associated with the East Ohio and Questar Gas Transactions, after-tax				$ 275
Impairment charge associated with the East Ohio Transaction, after-tax			$ 108