Operating Segments - Dominion Energy Gas (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Impairment of assets and other charges	$ 531	$ 312	$ 1,299	$ 1,147
Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
Impairment of assets and other charges	$ 482	$ 13	482	13
DETI
Segment Reporting Information [Line Items]
Impairment of assets and other charges			482
Asset impairment charges after tax			359
Operating Segments
Segment Reporting Information [Line Items]
After- tax net expenses			2,900	1,800
Operating Segments | Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program				42
Charge related to a voluntary retirement program, after-tax				31
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net expenses			3,100	2,100
Operating Segments | Corporate and Other | Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
After- tax net expenses			365	44
Operating Segments | Gas, Transmission & Storage | Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
After- tax net expenses			$ 365	$ 43