Operating Segments - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
External revenue	$ 744	$ 672
Comprehensive income (loss) available (attributable) to common shareholder	51	88
Dominion Energy South Carolina | Operating Segment
Segment Reporting Information [Line Items]
External revenue	744	672
Comprehensive income (loss) available (attributable) to common shareholder	97	89
Corporate and Other | Operating Segment
Segment Reporting Information [Line Items]
External revenue	0	0
Comprehensive income (loss) available (attributable) to common shareholder	$ (46)	$ (1)