Accumulated Other Comprehensive Income (Schedule of Changes in AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	$ 20,107
Ending balance		26,909
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[2]	13,047
Ending balance		12,944
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(235)	$ (302)
Other comprehensive income before reclassifications: gains (losses)		(24)	111
Amounts reclassified from AOCI: (gains) losses	[3]	(31)	8
Net current period other comprehensive income (loss)		(55)	119
Cumulative-effect of changes in accounting principle			(64)
Less other comprehensive income attributable to noncontrolling interest			1
Ending balance		(290)	(248)
Deferred Gains and Losses on Derivatives-Hedging Activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(13)	(12)
Other comprehensive income before reclassifications: gains (losses)		(7)	5
Net current period other comprehensive income (loss)		(7)	5
Cumulative-effect of changes in accounting principle			(3)
Ending balance		(20)	(10)
Deferred Gains and Losses on Derivatives-Hedging Activities | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(25)	(23)
Other comprehensive income before reclassifications: gains (losses)		(27)	13
Amounts reclassified from AOCI: (gains) losses	[3]	4	(3)
Net current period other comprehensive income (loss)		(23)	10
Cumulative-effect of changes in accounting principle			(5)
Ending balance		(48)	(18)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		2	747
Other comprehensive income before reclassifications: gains (losses)		16	(13)
Amounts reclassified from AOCI: (gains) losses	[3]		1
Net current period other comprehensive income (loss)		16	(12)
Cumulative-effect of changes in accounting principle			(732)
Ending balance		18	3
Unrealized Gains and Losses on Investment Securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		1	74
Other comprehensive income before reclassifications: gains (losses)		2
Net current period other comprehensive income (loss)		2
Cumulative-effect of changes in accounting principle			(73)
Ending balance		3	1
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,465)	(1,101)
Amounts reclassified from AOCI: (gains) losses	[3]	8	25
Net current period other comprehensive income (loss)		8	25
Cumulative-effect of changes in accounting principle			(227)
Ending balance		(1,457)	(1,303)
Unrecognized Pension and Other Postretirement Benefit Costs | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(144)	(75)
Amounts reclassified from AOCI: (gains) losses	[3]	1	1
Net current period other comprehensive income (loss)		1	1
Cumulative-effect of changes in accounting principle			(21)
Ending balance		(143)	(95)
Other Comprehensive Loss From Equity Method Investee
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(2)	(3)
Ending balance		(2)	(3)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,700)	(659)
Other comprehensive income before reclassifications: gains (losses)		(8)	98
Amounts reclassified from AOCI: (gains) losses	[3]	(23)	34
Net current period other comprehensive income (loss)		(31)	132
Cumulative-effect of changes in accounting principle			(1,023)
Less other comprehensive income attributable to noncontrolling interest			1
Ending balance		(1,731)	(1,551)
Accumulated Other Comprehensive Income (Loss) | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(12)	62
Other comprehensive income before reclassifications: gains (losses)		(5)	5
Net current period other comprehensive income (loss)		(5)	5
Cumulative-effect of changes in accounting principle			(76)
Ending balance		(17)	(9)
Accumulated Other Comprehensive Income (Loss) | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(169)	(98)
Other comprehensive income before reclassifications: gains (losses)		(27)	13
Amounts reclassified from AOCI: (gains) losses	[3]	5	(2)
Net current period other comprehensive income (loss)		(22)	11
Cumulative-effect of changes in accounting principle			(26)
Ending balance		$ (191)	$ (113)

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

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