Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	$ 29	$ 34
Operating Leases	100	41
Virginia Electric and Power Company
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	20	24
Operating Leases	$ 93	$ 35