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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax expense (benefit)		$ (10)	$ 136	$ (572)	$ 47
Net income (loss) including noncontrolling interests	[1],[2]	19	38	(1,753)	526
Net income (loss) attributable to Dominion Energy		(13)	38	(1,850)	520
Gas, Transmission & Storage
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue		1		4
Dominion Energy Gas Holdings, LLC | Gas, Transmission & Storage
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue		511	497	1,554	1,627
Operating Expense	[3]	208	317	1,311	1,029
Other income (loss)		(5)	13	27	42
Interest and related charges	[4]	267	76	366	224
Income (loss) before income taxes		31	117	(96)	416
Income tax expense (benefit)		(14)	117	(65)	42
Net income (loss) including noncontrolling interests		45	0	(31)	374
Noncontrolling interests		32	0	97	6
Net income (loss) attributable to Dominion Energy		13	0	(128)	368
Dominion Energy Gas Holdings, LLC | Q-Pipe Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating revenue		59	60	182	185
Operating Expense	[3]	16	31	78	100
Other income (loss)		1	1	3	3
Interest and related charges	[4]	5	5	15	15
Income (loss) before income taxes		39	25	92	73
Income tax expense (benefit)		5	19	19	6
Net income (loss) including noncontrolling interests		34	6	73	67
Net income (loss) attributable to Dominion Energy		$ 34	$ 6	$ 73	$ 67

[1] Includes income tax expense (benefit) of $(10) million and $136 million for the three months ended September 30, 2020 and 2019, respectively and $(572) million and $47 million for the nine months ended September 30, 2020 and 2019, 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] 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.