Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI by Component Net of Tax) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		$ (2,813)	$ (2,598)	$ (6,197)	$ (5,519)
Purchased gas		112	56	417	175
Electric fuel and other energy-related purchases		498	551	1,073	1,185
Interest and related charges		308	239	600	465
Other income		(60)	(72)	(176)	(126)
Income from operations including noncontrolling interests before income tax expense		(553)	(614)	(1,502)	(1,324)
Income tax expense		136	152	411	331
Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[1]	(422)	(368)	(912)	(799)
Purchased gas	[1]	38	16	81	50
Interest and related charges	[1]	24	23	47	45
Other income		(5)	(6)	(10)	(6)
Income from operations including noncontrolling interests before income tax expense		(122)	(172)	(287)	(331)
Income tax expense		45	67	102	128
Deferred (gains) and losses on derivatives-hedging activities: | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations including noncontrolling interests before income tax expense		(29)	(72)	(66)	(174)
Income tax expense		11	28	25	67
Income from continuing operations including noncontrolling interests		(18)	(44)	(41)	(107)
Deferred (gains) and losses on derivatives-hedging activities: | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations including noncontrolling interests before income tax expense		(19)	2	(1)	(2)
Income tax expense		7	(2)
Income from continuing operations including noncontrolling interests		(12)		(1)	(2)
Deferred (gains) and losses on derivatives-hedging activities: | Commodity contracts | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(19)	(87)	(81)	(201)
Purchased gas			2		8
Electric fuel and other energy-related purchases		(2)	3	(2)	6
Deferred (gains) and losses on derivatives-hedging activities: | Commodity contracts | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(1)		3	(4)
Deferred (gains) and losses on derivatives-hedging activities: | Interest rate contracts | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		11	8	23	11
Deferred (gains) and losses on derivatives-hedging activities: | Interest rate contracts | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		1		2
Deferred (gains) and losses on derivatives-hedging activities: | Foreign currency | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		(19)	2	(6)	2
Deferred (gains) and losses on derivatives-hedging activities: | Foreign currency | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		(19)	2	(6)	2
Unrealized (gains) and losses on investment securities: | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized (gain) loss on sale of securities		(11)	(20)	(64)	(30)
Impairment		5	7	14	14
Income from operations including noncontrolling interests before income tax expense		(6)	(13)	(50)	(16)
Income tax expense		2	5	18	6
Income from continuing operations including noncontrolling interests		(4)	(8)	(32)	(10)
Unrecognized pension and other postretirement benefit costs:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		21	14	42	28
Unrecognized pension and other postretirement benefit costs, income tax expense		(10)	(6)	(18)	(12)
Unrecognized pension and other postretirement benefit costs, net of tax		11	8	24	16
Unrecognized pension and other postretirement benefit costs: | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		2	1	3	2
Unrecognized pension and other postretirement benefit costs, income tax expense				(1)	(1)
Unrecognized pension and other postretirement benefit costs, net of tax		2	1	2	1
Unrecognized pension and other postretirement benefit costs: | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		(5)	(3)	(9)	(7)
Other operations and maintenance		26	17	51	35
Unrecognized pension and other postretirement benefit costs: | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		$ 2	$ 1	$ 3	$ 2

[1] See Note 17 for amounts attributable to related parties.