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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			$ 14,605
Total other comprehensive income		$ 54	$ 22	171	$ 3
Ending balance		16,280		16,280
Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income		(2)	9	1	(7)
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(250)	(241)	(280)	(176)
Other comprehensive income before reclassifications: gains (losses)		11	14	82	56
Amounts reclassified from AOCI: (gains) losses	[2]	(15)	(34)	(56)	(141)
Total other comprehensive income		(4)	(20)	26	(85)
Ending balance		(254)	(261)	(254)	(261)
Deferred Gains and Losses on Derivatives-Hedging Activities | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(23)	(34)	(24)	(17)
Other comprehensive income before reclassifications: gains (losses)		1	9	3	(6)
Amounts reclassified from AOCI: (gains) losses	[2]	(4)	(1)	(5)	(3)
Total other comprehensive income		(3)	8	(2)	(9)
Ending balance		(26)	(26)	(26)	(26)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		630	535	569	504
Other comprehensive income before reclassifications: gains (losses)		48	31	141	72
Amounts reclassified from AOCI: (gains) losses	[2]	(4)	(13)	(36)	(23)
Total other comprehensive income		44	18	105	49
Ending balance		674	553	674	553
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,058)	(781)	(1,082)	(797)
Other comprehensive income before reclassifications: gains (losses)		0	15	0	15
Amounts reclassified from AOCI: (gains) losses	[2]	14	9	38	25
Total other comprehensive income		14	24	38	40
Ending balance		(1,044)	(757)	(1,044)	(757)
Unrecognized Pension and Other Postretirement Benefit Costs | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(97)	(81)	(99)	(82)
Other comprehensive income before reclassifications: gains (losses)		0	0	0	0
Amounts reclassified from AOCI: (gains) losses	[2]	1	1	3	2
Total other comprehensive income		1	1	3	2
Ending balance		(96)	(80)	(96)	(80)
Other Comprehensive Income (Loss) From Equity Method Investee
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(4)	(6)	(6)	(5)
Other comprehensive income before reclassifications: gains (losses)		0	0	2	(1)
Amounts reclassified from AOCI: (gains) losses	[2]	0	0	0	0
Total other comprehensive income		0	0	2	(1)
Ending balance		(4)	(6)	(4)	(6)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(682)	(493)	(799)	(474)
Other comprehensive income before reclassifications: gains (losses)		59	60	225	142
Amounts reclassified from AOCI: (gains) losses	[2]	(5)	(38)	(54)	(139)
Total other comprehensive income		54	22	171	3
Ending balance		(628)	(471)	(628)	(471)
Total | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(120)	(115)	(123)	(99)
Other comprehensive income before reclassifications: gains (losses)		1	9	3	(6)
Amounts reclassified from AOCI: (gains) losses	[2]	(3)	0	(2)	(1)
Total other comprehensive income		(2)	9	1	(7)
Ending balance		$ (122)	$ (106)	$ (122)	$ (106)

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2016 has been derived from the audited Consolidated Balance Sheet at that date.

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