Income Taxes (Reconciliation of Income Taxes at the U.S. Statutory Federal Income Tax Rate) (Detail)		3 Months Ended		12 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017
Effective Income Tax Computation [Line Items]
U.S. statutory rate		21.00%	21.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit		4.40%	2.20%
Investment tax credits		(4.10%)	(1.50%)
Production tax credits		(0.40%)	(0.80%)
Reversal of excess deferred income taxes		(9.50%)	(5.10%)
Write-off of regulatory assets			(34.10%)
AFUDC - equity		(1.60%)	(1.40%)
Other, net		(2.50%)	(0.60%)
Effective tax rate		7.30%	(20.30%)
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		4.80%	4.60%
Investment tax credits		(6.40%)	(3.20%)
Production tax credits		(0.80%)	(1.00%)
Reversal of excess deferred income taxes		(8.10%)	(5.00%)
AFUDC - equity		(0.70%)
Other, net		0.30%	0.10%
Effective tax rate		10.10%	16.50%
Dominion Energy Gas Holdings, LLC
Effective Income Tax Computation [Line Items]
U.S. statutory rate		21.00%	21.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit		2.90%	3.40%
Reversal of excess deferred income taxes		(0.70%)	(0.70%)
AFUDC - equity		(0.40%)	(0.50%)
Other, net	[1]	(2.40%)	(3.30%)
Effective tax rate		20.40%	19.90%

[1] Includes (2.7)% and  (3.6) % relating to the absence of tax on noncontrolling interest in 2020 and 2019, respectively