Acquisitions and Dispositions (Schedule of Results of Operations of Disposal Groups Reported As Discontinued Operations) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax expense (benefit)		$ (6)	$ (10)	$ 5	$ (572)
Net income (loss) including noncontrolling interests	[1],[2]	65	19	119	(1,753)
Net income (loss) attributable to Dominion Energy		65	(13)	119	(1,850)
GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue		1	1	3	4
Income tax expense (benefit)		18
Disposition of GTS Operations | Q-Pipe Group
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue		62	59	188	182
Operating expense	[3]	24	16	52	78
Other income	[4]	26	1	27	3
Interest and related charges	[5]	7	5	17	15
Income (loss) before income taxes		57	39	146	92
Income tax expense (benefit)	[6]	12	5	29	19
Net income (loss) including noncontrolling interests		45	34	117	73
Net income (loss) attributable to Dominion Energy		$ 45	34	$ 117	73
Disposition of GTS Operations | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue			511		1,554
Operating expense	[3]		208		1,311
Other income	[4]		(5)		27
Interest and related charges	[5]		267		366
Income (loss) before income taxes			31		(96)
Income tax expense (benefit)	[6]		(14)		(65)
Net income (loss) including noncontrolling interests			45		(31)
Noncontrolling interests			32		97
Net income (loss) attributable to Dominion Energy			$ 13		$ (128)

[1] Includes income tax expense (benefit) of $(6) million and $(10) million for the three months ended September 30, 2021 and 2020, respectively, and $5 million and $(572) million for the nine months ended September 30, 2021 and 2020, respectively.

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

[3] 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.

[4] Q-Pipe Group includes a $25 million benefit associated with the termination of the Q-Pipe Transaction in the third quarter of 2021.

[5] GT&S Transaction includes a loss of $237 million 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

[6] Excludes $18 million income tax benefit recorded in the third quarter of 2021 associated with the GT&S Transaction.