Leases (Summary of Total Lease Cost) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Finance lease cost:
Finance lease cost, Amortization	$ 41	$ 40	$ 33
Finance lease cost, Interest	3	(3)
Operating lease cost	53	66	68
Short-term lease cost	31	32	20
Variable lease cost	4	5	8
Total lease cost	132	140	129
Virginia Electric and Power Company
Finance lease cost:
Finance lease cost, Amortization	15	12	7
Finance lease cost, Interest	3	1	1
Operating lease cost	32	30	36
Short-term lease cost	21	19	12
Variable lease cost	1	1	4
Total lease cost	$ 72	$ 63	$ 60