Asset Retirement Obligations (Changes to AROs) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018
Asset Retirement Obligations [Line Items]
AROs, Beginning balance		$ 2,532	[1]	$ 2,432
Obligations incurred during the period		2,413	[2]	20
Obligations settled during the period		(137)		(159)
AROs acquired in the SCANA Combination		577
Revisions in estimated cash flows		(324)	[3]	120	[2]
Accretion		213		119
AROs, Ending balance	[1]	5,274		2,532
Virginia Electric and Power Company
Asset Retirement Obligations [Line Items]
AROs, Beginning balance		1,445		1,365
Obligations incurred during the period		2,408	[2]	14
Obligations settled during the period		(81)		(119)
Revisions in estimated cash flows		(323)	[3]	120	[2]
Accretion		132		65
AROs, Ending balance		3,581		1,445
Dominion Energy Gas Holdings, LLC
Asset Retirement Obligations [Line Items]
AROs, Beginning balance		88	[4]	85
Obligations incurred during the period				3
Obligations settled during the period		(3)		(6)
Accretion		4		6
AROs, Ending balance	[4]	$ 89		$ 88

[1] Includes $282 million and $408 million reported in other current liabilities at December 31, 2018, and 2019, respectively.

[2] Reflects future ash pond and landfill closure costs at certain utility generation facilities. See Note 23 for further information.

[3] Reflects revisions to future ash pond and landfill closure costs at certain utility generation facilities as well as revisions for 20 year license extensions for regulated nuclear power stations in Virginia.

[4] Includes $74 million and $75 million reported in other deferred credits and other liabilities, with the remainder recorded in other current liabilities, at December 31, 2018 and 2019, respectively.