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, 2016	Sep. 30, 2015
Operating Loss Carryforwards [Line Items]
United States statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	3.70%	4.00%
Investment tax credits	(10.40%)	(3.50%)
Production tax credits	(0.80%)	(0.80%)
State legislative change	(0.80%)	(0.20%)
Other, net	(2.10%)	(0.70%)
Effective tax rate	24.60%	33.80%
Virginia Electric and Power Company
Operating Loss Carryforwards [Line Items]
United States statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	3.90%	4.20%
Investment tax credits	(0.00%)	(0.00%)
Production tax credits	(0.50%)	(0.50%)
State legislative change	0.00%	0.00%
Other, net	(0.50%)	(0.20%)
Effective tax rate	37.90%	38.50%
Dominion Gas Holdings, LLC
Operating Loss Carryforwards [Line Items]
United States statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	0.80%	4.10%
Investment tax credits	(0.00%)	(0.00%)
Production tax credits	(0.00%)	(0.00%)
State legislative change	0.00%	0.00%
Other, net	0.40%	0.40%
Effective tax rate	36.20%	39.50%