Equity (Schedule of Reclassifications out of AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Electric fuel and other energy related purchases		$ (2,938)	$ (2,814)	$ (2,301)
Interest and related charges		(1,773)	(1,493)	(1,205)
Other income	[1]	986	1,021	358
Income from operations before income tax expense		1,727	3,129	3,090
Income tax expense		351	580	(30)
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Electric fuel and other energy related purchases	[2]	(2,178)	(2,318)	(1,909)
Interest and related charges	[2]	(524)	(511)	(494)
Other income		98	22	76
Income from operations before income tax expense		1,413	1,582	2,314
Income tax expense		264	300	774
Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges	[3]	(311)	(174)	(60)
Other income		166	89	62
Income from operations before income tax expense		802	756	601
Income tax expense		101	124	(65)
Income from continuing operations including noncontrolling interests		701	632	$ 666
Deferred (gains) and losses on derivatives-hedging activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations before income tax expense		(83)	137
Income tax expense		21	(35)
Income from continuing operations including noncontrolling interests		(62)	102
Deferred (gains) and losses on derivatives-hedging activities | Commodity contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(146)	90
Electric fuel and other energy related purchases		3	(14)
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		54	48
Deferred (gains) and losses on derivatives-hedging activities | Foreign currency contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		6	13
Deferred (gains) and losses on derivatives-hedging activities | Virginia Electric and Power Company | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations before income tax expense		1	1
Income from continuing operations including noncontrolling interests		1	1
Deferred (gains) and losses on derivatives-hedging activities | Virginia Electric and Power Company | Interest rate contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		1	1
Deferred (gains) and losses on derivatives-hedging activities | Dominion Energy Gas Holdings, LLC | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations before income tax expense		7	26
Income tax expense		(2)	(7)
Income from continuing operations including noncontrolling interests		5	19
Deferred (gains) and losses on derivatives-hedging activities | Dominion Energy Gas Holdings, LLC | Commodity contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(4)	8
Deferred (gains) and losses on derivatives-hedging activities | Dominion Energy Gas Holdings, LLC | Interest rate contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		5	5
Deferred (gains) and losses on derivatives-hedging activities | Dominion Energy Gas Holdings, LLC | Foreign currency contracts | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		6	13
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		(5)	7
Income from operations before income tax expense		(5)	7
Income tax expense		1	(2)
Income from continuing operations including noncontrolling interests		(4)	5
Unrealized (gains) and losses on investment securities | Virginia Electric and Power Company | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized (gain) loss on sale of securities		2
Impairment		0
Income from operations before income tax expense		(2)
Income tax expense		1
Income from continuing operations including noncontrolling interests		1
Amortization of prior-service costs (credits) | Dominion Energy Gas Holdings, LLC | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		7	6
Unrecognized pension and other postretirement benefit costs, net of tax		5	4
Unrecognized pension and other postretirement benefit costs | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		(24)	21
Other income			120
Unrecognized pension and other postretirement benefit costs, before tax		89	99
Unrecognized pension and other postretirement benefit costs, income tax expense		(23)	(21)
Unrecognized pension and other postretirement benefit costs, net of tax			78
Unrecognized pension and other postretirement benefit costs | Dominion Energy Gas Holdings, LLC | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income		113
Unrecognized pension and other postretirement benefit costs, before tax		7	6
Unrecognized pension and other postretirement benefit costs, income tax expense		(2)	$ (2)
Unrecognized pension and other postretirement benefit costs, net of tax		$ 66

[1] See Note 9 for amounts attributable to related parties.

[2] See Note 25 for amounts attributable to affiliates.

[3] See Note 25 for amounts attributable to related parties.