Equity (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	$ (799)	$ (474)
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	46	40
Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(123)	(99)
Deferred gains and losses on derivatives-hedging activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(280)	(176)
Amount of tax	173	110
Deferred gains and losses on derivatives-hedging activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(8)	(7)
Amount of tax	5	4
Deferred gains and losses on derivatives-hedging activities | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(24)	(17)
Amount of tax	15	10
Unrealized gains and losses on investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	569	504
Amount of tax	(318)	(281)
Unrealized gains and losses on investment securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	54	47
Amount of tax	(35)	(30)
Unrecognized pension and other postretirement benefit costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(1,082)	(797)
Amount of tax	691	525
Unrecognized pension and other postretirement benefit costs | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(99)	(82)
Amount of tax	68	56
Other comprehensive loss from equity method investees
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total AOCI	(6)	(5)
Amount of tax	$ 4	$ 4