Income Taxes (Reconciliation of Income Taxes at the U.S. Statutory Federal Income Tax Rate) (Detail)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Effective Income Tax Computation [Line Items]
U.S. statutory rate	21.00%	21.00%
Increases (reductions) resulting from:
Recognition of deferred taxes - stock of subsidiary held for sale	9.40%
State taxes, net of federal benefit	3.30%	3.50%
Investment tax credits	(3.90%)	(3.80%)
Production tax credits	(0.40%)	(0.30%)
Reversal of excess deferred income taxes	(4.10%)	(2.20%)
Changes in state deferred taxes associated with assets held for sale	0.50%
AFUDC - equity	(0.60%)	(0.40%)
Other, net	0.20%
Effective tax rate	25.40%	17.80%
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	4.40%	4.50%
Investment tax credits	(6.70%)	(6.60%)
Production tax credits	(0.80%)	(0.60%)
Reversal of excess deferred income taxes	(3.00%)	(2.20%)
AFUDC - equity	(0.90%)	(0.70%)
Other, net	0.60%	0.30%
Effective tax rate	14.60%	15.70%