Leases (Cash Paid for Amounts Included in Measurement of Lease Liabilities) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee Lease Disclosure [Line Items]
Operating cash flows for finance leases	$ 13	$ 3	$ (3)
Operating cash flows for operating leases	105	82	103
Financing cash flows for finance leases	47	32	40
Virginia Electric and Power Company
Lessee Lease Disclosure [Line Items]
Operating cash flows for finance leases	4	3	1
Operating cash flows for operating leases	64	50	53
Financing cash flows for finance leases	$ 19	$ 12	$ 12