Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended			3 Months Ended				9 Months Ended
	Aug. 31, 2020	Dec. 31, 2019	May 31, 2019	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019
Segment Reporting Information [Line Items]
Asset early retirement expense					$ 89.0
Charge for Expected customer credit reinvestment offset								$ 200.0
Charge for Expected customer credit reinvestment offset, net of tax								149.0
Gain loss on investments held in nuclear decommissioning trust funds, after tax				$ (36.0)		$ (94.0)		(223.0)	$ (77.0)
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program									197.0
Charge related to a voluntary retirement program, after-tax									146.0
Asset early retirement expense after tax									275.0
Gain loss on investments held in nuclear decommissioning trust funds, after tax				$ 5.0		(15.0)		(36.0)	(29.0)
Benefit from revision of future closure costs									113.0
Benefit from revision of future closure costs, after tax									84.0
Variable Interest Entity (VIE) or Potential VIE, Information Unavailability | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Payment for contract termination			$ 135.0				$ 135.0		135.0
Payment for contract termination after tax							$ 100.0		100.0
SCANA
Segment Reporting Information [Line Items]
Merger and integration-related costs									408.0
Merger and integration-related costs, after tax									306.0
Charge related to a voluntary retirement program									394.0
Charge related to a voluntary retirement program, after-tax									295.0
Litigation settlement expense	$ 32.5	$ 192.5
Operating Segments
Segment Reporting Information [Line Items]
After- tax net expenses								1,300.0	1,800.0
Charge associated with certain merchant solar generation facilities								405.0
Charge associated with certain merchant solar generation facilities, net of tax								298.0
Gain loss on investments held in nuclear decommissioning trust funds									364.0
Gain loss on investments held in nuclear decommissioning trust funds, after tax									272.0
Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net expenses								815.0	653.0
Asset early retirement expense after tax								559.0
Charge for Expected customer credit reinvestment offset								200.0
Charge for Expected customer credit reinvestment offset, net of tax								149.0
Operating Segments | Fowler Ridge
Segment Reporting Information [Line Items]
Charge associated with the sale of Fowler Ridge								221.0
Charge associated with the sale of Fowler Ridge, net of tax								171.0
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
After- tax net expenses								3,400.0	1,700.0
Corporate and Other | Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net expenses								815.0	673.0
Dominion Energy South Carolina Inc | SCANA
Segment Reporting Information [Line Items]
Charge for refund of amounts from customers						1,000.0			1,000.0	$ 1,000.0
Charge for refund of amounts from customers, after tax									756.0
Charge related to a voluntary retirement program, after-tax									64.0
Litigation settlement expense									278.0
Litigation settlement expense, after tax									209.0
Charge for property, plant and equipment acquired but committed to forgo recovery									114.0
Charge for property, plant and equipment acquired but committed to forgo recovery, after tax									86.0
Dominion Energy South Carolina Inc | SCANA | NND Project
Segment Reporting Information [Line Items]
Tax benefit resulting from re-measurement of deferred income taxes as a result of the 2017 Tax Reform Act									198.0
Income tax related to regulatory assets acquired						$ 264.0			264.0
Dominion Energy Virginia | Virginia Legislation
Segment Reporting Information [Line Items]
Benefit from revision of future closure costs									113.0
Benefit from revision of future closure costs, after tax									84.0
Dominion Energy Virginia | Automated Meter Reading Program
Segment Reporting Information [Line Items]
Asset early retirement expense									160.0
Asset early retirement expense after tax									119.0
Dominion Energy Virginia | SCANA
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program, after-tax									149.0
Dominion Energy Virginia | Operating Segments
Segment Reporting Information [Line Items]
Gain loss on investments held in nuclear decommissioning trust funds, after tax									34.0
Dominion Energy Virginia | Operating Segments | Electric Generation Facilities
Segment Reporting Information [Line Items]
Asset early retirement expense								751.0	369.0
Asset early retirement expense after tax								$ 564.0	275.0
Gas Distribution | SCANA
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program, after-tax									55.0
Contracted Assets | SCANA
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program, after-tax									38.0
Contracted Assets | Operating Segments
Segment Reporting Information [Line Items]
Gain loss on investments held in nuclear decommissioning trust funds, after tax									$ 238.0