Accumulated Other Comprehensive Income (Schedule of Changes in AOCI by Component Net of Tax) (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		$ (386)		$ (317)	$ (416)	[1]	$ (324)
Other comprehensive income before reclassifications: gains (losses)		(74)		(56)	(36)		(192)
Amounts reclassified from AOCI: (gains) losses	[2]	(41)		(44)	(49)		99
Total other comprehensive loss		(115)		(100)	(85)		(93)
Ending balance		(501)		(417)	(501)		(417)
Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(86)		(75)	(86)	[3],[4]	(58)
Other comprehensive income before reclassifications: gains (losses)		3		(7)	2		(33)
Amounts reclassified from AOCI: (gains) losses	[2]	(1)		5	0		14
Total other comprehensive loss		2		(2)	2		(19)
Ending balance		(84)	[4]	(77)	(84)	[4]	(77)
Deferred gains and losses on derivatives-hedging activities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(146)		(353)	(178)		(288)
Other comprehensive income before reclassifications: gains (losses)		(7)		(58)	25		(267)
Amounts reclassified from AOCI: (gains) losses	[2]	(53)		(31)	(53)		113
Total other comprehensive loss		(60)		(89)	(28)		(154)
Ending balance		(206)		(442)	(206)		(442)
Deferred gains and losses on derivatives-hedging activities | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(22)		(16)	(20)		3
Other comprehensive income before reclassifications: gains (losses)		3		(7)	2		(33)
Amounts reclassified from AOCI: (gains) losses	[2]	(2)		4	(3)		11
Total other comprehensive loss		1		(3)	(1)		(22)
Ending balance		(21)		(19)	(21)		(19)
Unrealized gains and losses on investment securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		519		534	548		474
Other comprehensive income before reclassifications: gains (losses)		(59)		2	(55)		80
Amounts reclassified from AOCI: (gains) losses	[2]	(2)		(21)	(35)		(39)
Total other comprehensive loss		(61)		(19)	(90)		41
Ending balance		458		515	458		515
Unrecognized pension and other postretirement benefit costs
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(754)		(493)	(782)		(510)
Other comprehensive income before reclassifications: gains (losses)		(9)		0	(6)		0
Amounts reclassified from AOCI: (gains) losses	[2]	14		8	39		25
Total other comprehensive loss		5		8	33		25
Ending balance		(749)		(485)	(749)		(485)
Unrecognized pension and other postretirement benefit costs | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(64)		(59)	(66)		(61)
Other comprehensive income before reclassifications: gains (losses)		0		0	0		0
Amounts reclassified from AOCI: (gains) losses	[2]	1		1	3		3
Total other comprehensive loss		1		1	3		3
Ending balance		(63)		(58)	(63)		(58)
Other comprehensive income (loss) from equity method investee
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(5)		(5)	(4)		0
Other comprehensive income before reclassifications: gains (losses)		1		0	0		(5)
Amounts reclassified from AOCI: (gains) losses	[2]	0		0	0		0
Total other comprehensive loss		1		0	0		(5)
Ending balance		$ (4)		$ (5)	$ (4)		$ (5)

[1] Dominion’s Consolidated Balance Sheet at December 31, 2014 has been derived from the audited Consolidated Financial Statements at that date.

[2] See table below for details about these reclassifications.

[3] Dominion Gas’ Consolidated Balance Sheet at December 31, 2014 has been derived from the audited Consolidated Financial Statements at that date.

[4] See Note 18 for amounts attributable to related parties.