Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended		3 Months Ended				12 Months Ended
	Aug. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Asset early retirement expense							$ 114.0	$ 134.0
Charge associated with the sale of Fowler Ridge, net of tax				$ 170.0
Charge for expected CCRO, net of tax				149.0
Charges associated with legislation enacted related to customer arrears, net of tax			$ 94.0
Gain loss on investments							412.0	626.0	$ (102.0)
2017 Tax Reform Act							0.0	0.0	46.0
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Asset early retirement expense							85.0	81.0
Charge for expected CCRO, net of tax				$ 149.0
Charges associated with legislation enacted related to customer arrears, net of tax			$ 94.0
2017 Tax Reform Act							0.0	0.0	21.0
Payment for contract termination								135.0
Payment for contract termination after tax								100.0
SCANA
Segment Reporting Information [Line Items]
Litigation settlement, amount received from SCANA	$ 32.5	$ 192.5
Merger and integration-related costs						$ 1,300.0		427.0
Merger and integration-related costs, after tax								320.0
Charge related to a voluntary retirement program								394.0
Charge related to a voluntary retirement program, after-tax								295.0
Electric Generation Facilities
Segment Reporting Information [Line Items]
Asset early retirement expense after tax					$ 566.0
Electric Generation Facilities | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Asset early retirement expense after tax					$ 561.0
Operating Segments
Segment Reporting Information [Line Items]
After-tax net expense (income)							1,200.0	1,900.0	196.0
Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After-tax net expense (income)							863.0
Asset early retirement expense after tax							559.0	257.0
Charge for expected CCRO							130.0
Charge for expected CCRO, net of tax							97.0
Charges associated with legislation enacted related to customer arrears							127.0
Charges associated with legislation enacted related to customer arrears, net of tax							94.0
Charge related to a voluntary retirement program								198.0
Charge related to a voluntary retirement program, after-tax								146.0
Benefit from revision of future closure costs								113.0
Benefit from revision of future closure costs, after tax								84.0
One-time rate credit amount									215.0
One-time rate credit amount after tax									160.0
Charge associated with major storm damage and service restoration									70.0
Charge associated with major storm damage and service restoration, after tax									52.0
Operating Segments | Virginia Electric and Power Company | Virginia Regulation
Segment Reporting Information [Line Items]
Charge associated with asset retirement obligations for ash ponds and landfills at certain utility generation facilities									81.0
Environmental remediation expense net of tax									60.0
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments							335.0	553.0	170.0
Gain loss on investments, net of tax							264.0	411.0	134.0
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
After-tax net expense (income)							3,700.0	1,800.0	(117.0)
After- tax net expense (income) for specific items							3,400.0	1,500.0	(322.0)
Corporate and Other | Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After-tax net expense (income)							863.0	634.0	312.0
After- tax net expense (income) for specific items							915.0	627.0	312.0
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 | SCANA
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program, after-tax								151.0
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 | Operating Segments
Segment Reporting Information [Line Items]
Charge for expected CCRO							130.0
Charge for expected CCRO, net of tax							97.0
Charges associated with legislation enacted related to customer arrears							127.0
Charges associated with legislation enacted related to customer arrears, net of tax							94.0
Charge associated with major storm damage and service restoration									70.0
Charge associated with major storm damage and service restoration, after tax									52.0
Dominion Energy Virginia | Operating Segments | Virginia Legislation
Segment Reporting Information [Line Items]
One-time rate credit amount									215.0
One-time rate credit amount after tax									160.0
Dominion Energy Virginia | Operating Segments | Virginia Regulation
Segment Reporting Information [Line Items]
Charge associated with asset retirement obligations for ash ponds and landfills at certain utility generation facilities									81.0
Environmental remediation expense net of tax									60.0
Dominion Energy Virginia | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments, net of tax							27.0	49.0	14.0
Dominion Energy Virginia | Operating Segments | Electric Generation Facilities
Segment Reporting Information [Line Items]
Asset early retirement expense							751.0	346.0
Asset early retirement expense after tax							564.0	257.0
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]
Charge associated with certain merchant solar generation facilities							405.0
Charge associated with certain merchant solar generation facilities, net of tax							325.0
Charge associated with the sale of Fowler Ridge							221.0
Charge associated with the sale of Fowler Ridge, net of tax							171.0
Benefit associated with sale of certain merchant generation facilities									282.0
Benefit associated with sale of certain merchant generation facilities, after tax									229.0
Contracted Assets | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments, net of tax							237.0	362.0	$ 120.0
Dominion Energy South Carolina Inc | SCANA
Segment Reporting Information [Line Items]
Charge for refund of amounts from customers, current						$ 137.0
Charge for refund of amounts from customers, after tax								756.0
Dominion Energy South Carolina Inc | SCANA | NND Project
Segment Reporting Information [Line Items]
2017 Tax Reform Act								194.0
Income tax regulatory assets		258.0						258.0
Dominion Energy South Carolina Inc | Operating Segments
Segment Reporting Information [Line Items]
Litigation settlement, amount received from SCANA							117.0	641.0
Litigation settlement expense, after tax							$ 93.0	480.0
Charge for refund of amounts from customers, current		$ 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								75.0
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
Gas Distribution | SCANA
Segment Reporting Information [Line Items]
Charge related to a voluntary retirement program, after-tax								$ 56.0