Variable Interest Entities - (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Payables to affiliates	$ 255	$ 121
Variable Interest Entity Not Primary Beneficiary | Distribution | Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline
Variable Interest Entity [Line Items]
Initial membership interest percentage	53.00%
Variable Interest Entity Not Primary Beneficiary | Virginia Electric and Power Company | DES
Variable Interest Entity [Line Items]
Shared Services Purchased	$ 396	380	$ 349
Payables to affiliates	$ 28	$ 20
Variable Interest Entity Not Primary Beneficiary | Partnership Interest | Cove Point
Variable Interest Entity [Line Items]
Initial membership interest percentage	50.00%