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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[1]			$ 12,664
Total other comprehensive income (loss)		$ 22	$ (115)	3	$ (85)
Ending balance		14,958		14,958
Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[2]			3,318
Total other comprehensive income (loss)		9	2	(7)	2
Ending balance		3,447		3,447
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(493)	(386)	(474)	(416)
Other comprehensive income before reclassifications: gains (losses)		60	(74)	142	(36)
Amounts reclassified from AOCI: (gains) losses	[3]	(38)	(41)	(139)	(49)
Total other comprehensive income (loss)		22	(115)	3	(85)
Ending balance		(471)	(501)	(471)	(501)
Total | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(115)	(86)	(99)	(86)
Other comprehensive income before reclassifications: gains (losses)		9	3	(6)	2
Amounts reclassified from AOCI: (gains) losses	[3]	0	(1)	(1)	0
Total other comprehensive income (loss)		9	2	(7)	2
Ending balance		(106)	(84)	(106)	(84)
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(241)	(146)	(176)	(178)
Other comprehensive income before reclassifications: gains (losses)		14	(7)	56	25
Amounts reclassified from AOCI: (gains) losses	[3]	(34)	(53)	(141)	(53)
Total other comprehensive income (loss)		(20)	(60)	(85)	(28)
Ending balance		(261)	(206)	(261)	(206)
Deferred Gains and Losses on Derivatives-Hedging Activities | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(34)	(22)	(17)	(20)
Other comprehensive income before reclassifications: gains (losses)		9	3	(6)	2
Amounts reclassified from AOCI: (gains) losses	[3]	(1)	(2)	(3)	(3)
Total other comprehensive income (loss)		8	1	(9)	(1)
Ending balance		(26)	(21)	(26)	(21)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		535	519	504	548
Other comprehensive income before reclassifications: gains (losses)		31	(59)	72	(55)
Amounts reclassified from AOCI: (gains) losses	[3]	(13)	(2)	(23)	(35)
Total other comprehensive income (loss)		18	(61)	49	(90)
Ending balance		553	458	553	458
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(781)	(754)	(797)	(782)
Other comprehensive income before reclassifications: gains (losses)		15	(9)	15	(6)
Amounts reclassified from AOCI: (gains) losses	[3]	9	14	25	39
Total other comprehensive income (loss)		24	5	40	33
Ending balance		(757)	(749)	(757)	(749)
Unrecognized Pension and Other Postretirement Benefit Costs | Dominion Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(81)	(64)	(82)	(66)
Other comprehensive income before reclassifications: gains (losses)		0	0	0	0
Amounts reclassified from AOCI: (gains) losses	[3]	1	1	2	3
Total other comprehensive income (loss)		1	1	2	3
Ending balance		(80)	(63)	(80)	(63)
Other Comprehensive Income (Loss) From Equity Method Investee
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(6)	(5)	(5)	(4)
Other comprehensive income before reclassifications: gains (losses)		0	1	(1)	0
Amounts reclassified from AOCI: (gains) losses	[3]	0	0	0	0
Total other comprehensive income (loss)		0	1	(1)	0
Ending balance		$ (6)	$ (4)	$ (6)	$ (4)

[1] Dominion’s Consolidated Balance Sheet at December 31, 2015 has been derived from the audited Consolidated Financial Statements at that date.

[2] Dominion Gas’ Consolidated Balance Sheet at December 31, 2015 has been derived from the audited Consolidated Financial Statements at that date.

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