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	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 124	$ 71	$ 95	$ 107
Total realized and unrealized gains (losses):
Included in earnings	(7)	(9)	(23)	1
Included in other comprehensive income (loss)	0	5	2	(7)
Included in regulatory assets/liabilities	(37)	47	(5)	18
Settlements	9	10	27	1
Transfers out of Level 3	0	(1)	(7)	3
Ending balance	89	123	89	123
The amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets/liabilities still held at the reporting date	0	1	0	1
Virginia Electric and Power Company
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	125	73	93	102
Total realized and unrealized gains (losses):
Included in earnings	(7)	(10)	(24)	(1)
Included in regulatory assets/liabilities	(37)	47	(5)	18
Settlements	7	10	24	1
Ending balance	88	120	88	120
Dominion Gas Holdings, LLC
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	0	(1)	6	2
Total realized and unrealized gains (losses):
Included in earnings	0	0	0	1
Included in other comprehensive income (loss)	0	5	2	(7)
Settlements	0	0	0	(1)
Transfers out of Level 3	0	0	(8)	9
Ending balance	$ 0	$ 4	$ 0	$ 4