Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI by Component Net of Tax) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		$ (3,179)	$ (3,132)	$ (9,376)	$ (8,651)
Purchased gas		24	77	441	252
Electric fuel and other energy-related purchases		638	606	1,711	1,791
Interest and related charges		305	250	905	715
Other income		(73)	(63)	(249)	(189)
Impairment		4	5	18	18
Income from operations including noncontrolling interests before income tax expense		(968)	(958)	(2,470)	(2,282)
Income tax expense		272	230	683	561
Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[1]	(401)	(382)	(1,313)	(1,181)
Purchased gas	[1]	19	21	100	71
Interest and related charges	[1]	25	23	72	68
Other income		(6)	(2)	(16)	(8)
Income from operations including noncontrolling interests before income tax expense		(191)	(117)	(478)	(448)
Income tax expense		74	34	176	162
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		(25)	(55)	(91)	(229)
Income tax expense		10	21	35	88
Income from continuing operations including noncontrolling interests		(15)	(34)	(56)	(141)
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		(7)	(3)	(8)	(5)
Income tax expense		3	2	3	2
Income from continuing operations including noncontrolling interests		(4)	(1)	(5)	(3)
Deferred (gains) and losses on derivatives-hedging activities: | Commodity contracts | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(32)	(64)	(114)	(266)
Purchased gas			1		9
Electric fuel and other energy-related purchases		1	1	(1)	8
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		2	(1)	4	(6)
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		16	10	39	21
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	1	3	2
Deferred (gains) and losses on derivatives-hedging activities: | Foreign currency | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		(10)	(3)	(15)	(1)
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		(10)	(3)	(15)	(1)
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		(10)	(25)	(74)	(55)
Impairment		4	5	18	19
Income from operations including noncontrolling interests before income tax expense		(6)	(20)	(56)	(36)
Income tax expense		2	7	20	13
Income from continuing operations including noncontrolling interests		(4)	(13)	(36)	(23)
Unrecognized pension and other postretirement benefit costs:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		21	13	63	41
Unrecognized pension and other postretirement benefit costs, income tax expense		(7)	(4)	(25)	(16)
Unrecognized pension and other postretirement benefit costs, net of tax		14	9	38	25
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	2	5	4
Unrecognized pension and other postretirement benefit costs, income tax expense		(1)	(1)	(2)	(2)
Unrecognized pension and other postretirement benefit costs, net of tax		1	1	3	2
Unrecognized pension and other postretirement benefit costs: | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		(5)	(4)	(16)	(11)
Other operations and maintenance		26	17	79	52
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	$ 2	$ 5	$ 4

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