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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		$ (3,132)	$ (2,971)	$ (8,651)	$ (9,127)
Purchased gas		77	85	252	446
Electric fuel and other energy-related purchases		606	636	1,791	2,180
Interest and related charges		250	230	715	674
Other income		(63)	(11)	(189)	(127)
Impairment		5	16	18	27
Income from operations including noncontrolling interests before income tax expense		(958)	(904)	(2,282)	(2,351)
Income tax expense		230	305	561	794
Other operations and maintenance		765	564	2,133	1,875
Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[1]	(382)	(365)	(1,181)	(1,291)
Purchased gas	[1]	21	8	71	103
Interest and related charges		23	18	68	53
Other income		(7)	(4)	(22)	(17)
Income from operations including noncontrolling interests before income tax expense		(117)	(188)	(448)	(590)
Income tax expense		34	77	162	233
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		(55)	(83)	(229)	(87)
Income tax expense		21	30	88	34
Income from continuing operations including noncontrolling interests		(34)	(53)	(141)	(53)
Deferred (gains) and losses on derivatives-hedging activities: | Amounts Reclassified From AOCI | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations including noncontrolling interests before income tax expense		(3)	(3)	(5)	(4)
Income tax expense		2	1	2	1
Income from continuing operations including noncontrolling interests		(1)	(2)	(3)	(3)
Deferred (gains) and losses on derivatives-hedging activities: | Commodity contracts | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(64)	(87)	(266)	(103)
Purchased gas		1	2	9	9
Electric fuel and other energy-related purchases		1		8
Deferred (gains) and losses on derivatives-hedging activities: | Commodity contracts | Amounts Reclassified From AOCI | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(1)	(3)	(6)	(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		10	2	21	7
Deferred (gains) and losses on derivatives-hedging activities: | Interest rate contracts | Amounts Reclassified From AOCI | Dominion 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		(3)		(1)
Deferred (gains) and losses on derivatives-hedging activities: | Foreign currency | Amounts Reclassified From AOCI | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		(3)		(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		(25)	(18)	(55)	(82)
Impairment		5	16	19	27
Income from operations including noncontrolling interests before income tax expense		(20)	(2)	(36)	(55)
Income tax expense		7	0	13	20
Income from continuing operations including noncontrolling interests		(13)	(2)	(23)	(35)
Unrecognized pension and other postretirement benefit costs:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		13	21	41	64
Unrecognized pension and other postretirement benefit costs, income tax expense		(4)	(7)	(16)	(25)
Unrecognized pension and other postretirement benefit costs, net of tax		9	14	25	39
Unrecognized pension and other postretirement benefit costs: | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		2	2	4	6
Unrecognized pension and other postretirement benefit costs, income tax expense		(1)	(1)	(2)	(3)
Unrecognized pension and other postretirement benefit costs, net of tax		1	1	2	3
Prior service (credit) costs | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		(4)	(3)	(11)	(9)
Actuarial (gains) losses | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		17	24	52	73
Actuarial (gains) losses | Amounts Reclassified From AOCI | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operations and maintenance		$ 2	$ 2	$ 4	$ 6

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