Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[1]	$ (4,496)	$ (3,858)
Purchased gas		427	730
Interest and related charges		490	469
Other income (expense)		399	(388)
Income from operations before income tax expense		258	563
Income tax expense (benefit)		(19)	114
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[2]	(1,930)	(1,965)
Interest and related charges	[2]	126	135
Other income (expense)		52	(37)
Income from operations before income tax expense		311	(24)
Income tax expense (benefit)		(31)	4
Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue	[3]	(556)	(566)
Purchased gas	[3]	8	12
Interest and related charges	[3]	58	87
Other income (expense)	[3]	(49)	(42)
Income tax expense (benefit)		52	43
Income (loss) including noncontrolling interests, net of tax		(202)	(172)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations before income tax expense		29	(41)
Income tax expense (benefit)		(7)	10
Income (loss) including noncontrolling interests, net of tax		22	(31)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income from operations before income tax expense		8	3
Income tax expense (benefit)		(2)
Income (loss) including noncontrolling interests, net of tax		6	3
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Commodity contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue		(7)	(54)
Purchased gas		3	(3)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Commodity contracts | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Operating revenue			(2)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Interest rate contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		27	10
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Interest rate contracts | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and related charges		2	(1)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Foreign currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense)		6	6
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Amounts Reclassified From AOCI | Foreign currency | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense)		6	6
Unrealized (gains) and losses on investment securities: | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized (gains) losses on sale of securities		(13)
Income from operations before income tax expense		(13)
Income tax expense (benefit)		4
Income (loss) including noncontrolling interests, net of tax		(9)
Unrealized (gains) and losses on investment securities: | Amounts Reclassified From AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized (gains) losses on sale of securities		2
Income from operations before income tax expense		2
Income tax expense (benefit)		(1)
Income (loss) including noncontrolling interests, net of tax		1
Amortization of prior-service costs (credits) | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense)		(6)	(5)
Amortization of actuarial losses | Amounts Reclassified From AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense)		30	27
Unrecognized pension and other postretirement benefit costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		24	22
Unrecognized pension and other postretirement benefit costs, income tax expense (benefit)		(5)	(14)
Unrecognized pension and other postretirement benefit costs, net of tax		19	8
Unrecognized pension and other postretirement benefit costs | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrecognized pension and other postretirement benefit costs, before tax		2	2
Unrecognized pension and other postretirement benefit costs, income tax expense (benefit)		(1)	(1)
Unrecognized pension and other postretirement benefit costs, net of tax		1	1
Unrecognized pension and other postretirement benefit costs | Amounts Reclassified From AOCI | Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense)		$ 2	$ 2

[1] See Note 10 for amounts attributable to related parties.

[2] See Note 19 for amounts attributable to affiliates.

[3] See Note 19 for amounts attributable to related parties.