Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	$ 100	$ 51
Operating leases	83	243
Virginia Electric and Power Company
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	89	44
Operating leases	$ 67	$ 209