Operating Segments (Narrative) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Corporate and Other
Segment Reporting Information [Line Items]
After- tax net expenses	$ 261
South Carolina Electric Base Rate Case
Segment Reporting Information [Line Items]
Settlement charges	266
Settlement charges net of tax	199
Dominion Energy South Carolina, Inc. [Member]
Segment Reporting Information [Line Items]
Litigation charges	70
Litigation charges, after tax	$ 53