Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	$ 19	$ 22
Operating Leases	38	7
Virginia Electric and Power Company
Schedule Of Supplemental Cash Flow Information [Line Items]
Financing leases	14	$ 17
Operating Leases	$ 33