Income Taxes (Reconciliation of Income Taxes at the U.S. Statutory Federal Rate as Compared to the Income Tax Expense Recorded in Our Consolidated Statements of Income) (Details)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	2.90%	3.70%
Investment tax credits	(5.70%)	(10.40%)
Production tax credits	(0.70%)	(0.80%)
State legislative change	0.00%	(0.80%)
AFUDC - equity	(1.30%)	(0.70%)
Other, net	(2.60%)	(1.40%)
Effective tax rate	27.60%	24.60%
Virginia Electric and Power Company
Income Taxes [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	3.70%	3.90%
Investment tax credits	(0.80%)	(0.00%)
Production tax credits	(0.50%)	(0.50%)
State legislative change	0.00%	0.00%
AFUDC - equity	(0.60%)	(0.60%)
Other, net	0.20%	0.10%
Effective tax rate	37.00%	37.90%
Dominion Energy Gas Holdings, LLC
Income Taxes [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	2.70%	0.80%
Investment tax credits	(0.00%)	(0.00%)
Production tax credits	(0.00%)	(0.00%)
State legislative change	0.00%	0.00%
AFUDC - equity	(0.80%)	(0.10%)
Other, net	(0.10%)	0.50%
Effective tax rate	36.80%	36.20%