Fair Value Measurements (Net Change in the Assets and Liabilities Measured at Fair Value on a Recurring Basis and Included in the Level 3 Fair Value Category) (Details) - Commodity - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginnning balance	$ 95	$ 107	$ (16)
Included in earnings	(35)	(5)	97
Included in other comprehensive income (loss)	0	(9)	7
Included in regulatory assets/liabilities	(39)	(4)	109
Settlements	38	9	(88)
Purchases	87	0	0
Transfers out of Level 3	(7)	(3)	(2)
Ending balance	139	95	107
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets still held at the reporting date	(1)	2	6
Virginia Electric and Power Company
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginnning balance	93	102	(7)
Included in earnings	(35)	(13)	96
Included in regulatory assets/liabilities	(37)	(5)	109
Settlements	35	13	(96)
Purchases	87	0	0
Transfers out of Level 3	0	(4)	0
Ending balance	143	93	102
Dominion Gas Holdings, LLC
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginnning balance	6	2	(6)
Included in earnings	0	1	2
Included in other comprehensive income (loss)	0	(5)	10
Settlements	0	(1)	(4)
Transfers out of Level 3	(8)	9	0
Ending balance	$ (2)	$ 6	$ 2