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)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Loss Carryforwards [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	2.80%	4.30%
Investment tax credits	(4.20%)	(10.90%)
Production tax credits	(0.80%)	(0.80%)
Other, net	(3.80%)	(2.40%)
Effective tax rate	29.00%	25.20%
Virginia Electric and Power Company
Operating Loss Carryforwards [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	3.80%	4.20%
Investment tax credits	(0.80%)	(1.30%)
Production tax credits	(0.60%)	(0.60%)
Other, net	(0.60%)	(0.60%)
Effective tax rate	36.80%	36.70%
Dominion Gas Holdings, LLC
Operating Loss Carryforwards [Line Items]
U.S. statutory rate	35.00%	35.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	0.30%	3.90%
Investment tax credits	(0.00%)	(0.00%)
Production tax credits	(0.00%)	(0.00%)
Other, net	(0.60%)	(0.10%)
Effective tax rate	34.70%	38.80%