Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 103	$ 145	$ 222
Increases-prior period positions	9	2	24
Decreases-prior period positions	(44)	(40)	(26)
Increases-current period positions	6	8	16
Settlements with tax authorities	(8)	(5)	0
Expiration of statutes of limitations	(2)	(7)	(91)
Balance at December 31	64	103	145
Virginia Electric and Power Company
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	12	36	39
Increases-prior period positions	4	0	2
Decreases-prior period positions	(3)	(25)	(16)
Increases-current period positions	0	1	11
Settlements with tax authorities	0	0	0
Expiration of statutes of limitations	0	0	0
Balance at December 31	13	12	36
Dominion Gas Holdings, LLC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	29	29	29
Increases-prior period positions	1	0	0
Decreases-prior period positions	(19)	0	0
Increases-current period positions	0	0	0
Settlements with tax authorities	(4)	0	0
Expiration of statutes of limitations	0	0	0
Balance at December 31	$ 7	$ 29	$ 29