Acquisitions and Dispositions (Schedule of Results of Operations of Disposal Groups Reported As Discontinued Operations) (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax expense (benefit)										$ (204)		$ 142		$ 58
Net income (loss) including noncontrolling interests		$ (125)	$ 19	$ (2,001)	$ 229	$ 190	$ 38	$ 257	$ 231	(1,878)	[1],[2]	716	[1],[2]	452	[1],[2]
Net income (loss) attributable to Dominion Energy										(1,984)		705		360
GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue										4		6		6
Disposition of GT&S Operations to BHE | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue										1,710	[3]	2,213		2,134
Operating Expense	[4],[5]									1,289	[3]	1,367		1,663
Other income (loss)										88	[3]	58		68
Interest and related charges	[6]									372	[3]	267		183
Income (loss) before income taxes										137	[3]	637		356
Income tax expense (benefit)										334	[3]	120		40
Net income (loss) including noncontrolling interests										(197)	[3]	517		316
Noncontrolling interests										106	[3]	11		92
Net income (loss) attributable to Dominion Energy										(303)	[3]	506		224
Disposition of GT&S Operations to BHE | Q-Pipe Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue										246		251		247
Operating Expense	[4],[5]									96		131		135
Other income (loss)										1		4		5
Interest and related charges	[6]									20		20		20
Income (loss) before income taxes										131		104		97
Income tax expense (benefit)										(9)		23		18
Net income (loss) including noncontrolling interests										140		81		79
Net income (loss) attributable to Dominion Energy										$ 140		$ 81		$ 79

[1] Includes income tax expense (benefit) of $(204) million, $142 million and $58 million for the years ended December 31, 2020, 2019 and 2018, respectively

[2] See Note 9 for amounts attributable to related parties

[3] Operations associated with the GT&S Transaction are through the November 1, 2020 settlement date.

[4] GT&S Transaction includes a charge of $482 million ($359 million after-tax) recorded in the second quarter of 2020 associated with the probable abandonment of a significant portion of the Supply Header Project as well as the establishment of a $75 million ARO as a result of the cancellation of the Atlantic Coast Pipeline Project.

[5] GT&S Transaction includes gains on sales of assets recorded in 2018 totaling $115 million ($83 million after-tax), associated with the conveyance of Marcellus Shale and Utica and Point Pleasant Shale acreage underneath its natural gas storage fields.

[6] GT&S Transaction includes a loss of $237 million ($178 million after-tax) recorded in the third quarter of 2020 associated with cash flow hedges of debt-related items that were determined to be probable of not occurring.