Income Taxes (Reconciliation of Income Taxes at the U.S. Statutory Federal Income Tax Rate) (Detail)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Effective Income Tax Computation [Line Items]
U.S. statutory rate	21.00%	21.00%
Increases (reductions) resulting from:
Recognition of taxes - sale of subsidiary stock	0.00%	28.40%
State taxes, net of federal benefit	3.90%	13.10%
Investment tax credits	(3.20%)	(23.60%)
Production tax credits	(0.60%)	(2.60%)
Reversal of excess deferred income taxes	(2.60%)	(15.60%)
Changes in state deferred taxes associated with assets held for sale	1.30%	1.60%
AFUDC - equity	(0.10%)	(1.60%)
Other, net	(0.90%)	(1.60%)
Effective tax rate	18.80%	19.10%
Virginia Electric and Power Company
Effective Income Tax Computation [Line Items]
U.S. statutory rate	21.00%	21.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	4.60%	4.40%
Investment tax credits	(0.30%)	(8.90%)
Production tax credits	(0.90%)	(1.00%)
Reversal of excess deferred income taxes	(2.60%)	(3.70%)
AFUDC - equity	0.00%	(0.80%)
Other, net	(0.30%)	0.50%
Effective tax rate	21.50%	11.50%