Income Taxes (Reconciliation of Income Taxes at the U.S. Statutory Federal Income Tax Rate) (Detail)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 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	25.00%
State taxes, net of federal benefit	7.90%	2.30%
Investment tax credits	(9.80%)	(5.30%)
Production tax credits	(1.10%)	(0.40%)
Reversal of excess deferred income taxes	(10.20%)	(3.50%)
State legislative change		(1.50%)
Changes in state deferred taxes associated with assets held for sale	1.40%
AFUDC - equity	(1.30%)	(0.50%)
Other, net	0.20%	(0.40%)
Effective tax rate	33.10%	11.70%
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	(6.90%)	(5.80%)
Production tax credits	(1.00%)	(0.60%)
Reversal of excess deferred income taxes	(3.90%)	(2.10%)
State legislative change		(1.70%)
AFUDC - equity	(1.00%)	(0.60%)
Other, net	0.60%	0.30%
Effective tax rate	13.20%	15.00%