Commitments and Contingencies (Narrative) (Detail) $ in Millions	1 Months Ended												3 Months Ended			6 Months Ended		12 Months Ended
	Jul. 31, 2020 USD ($)	Apr. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)		Jul. 31, 2019 USD ($)	May 31, 2019 T	Feb. 28, 2019 USD ($)	Aug. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Facility Indicator site gal	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Impairment of assets and other charges													$ 531.0		$ 312.0	$ 1,299.0	$ 1,147.0
Property, plant and equipment, net				$ 69,082.0	[1]								67,980.0			67,980.0		$ 69,082.0	[1]
Nuclear Obligations
Loss Contingencies [Line Items]
Liability protection per nuclear incident available amount													13,800.0	$ 13,900.0
Common Stock
Loss Contingencies [Line Items]
Litigation settlement, benefit fund			$ 320.0
DESC Ratepayer Case
Loss Contingencies [Line Items]
Litigation settlement, benefit fund			520.0
SCANA
Loss Contingencies [Line Items]
Reserves for SCANA legal proceedings				696.0	[1]								538.0			538.0		696.0	[1]
Other expense																25.0
Other expense, after tax																25.0
Impairment of assets and other charges															100.0		278.0
Impairment of assets and other charges, after tax															75.0		208.0
Escrow account			$ 160.0											$ 160.0
Litigation settlement, amount received from SCANA				192.5
Payment for civil monetary penalty from SCANA		$ 25.0
SCANA | Subsequent Event
Loss Contingencies [Line Items]
Litigation settlement, amount received from SCANA	$ 32.5
SCANA | DESC Ratepayer Case
Loss Contingencies [Line Items]
Escrow account																				$ 2,000.0
Credit in future electric rate relief																				2,000.0
Cash payment						$ 117.0														115.0
Property, plant and equipment, net						$ 54.0							26.0			26.0
SCANA | Other Receivables
Loss Contingencies [Line Items]
Insurance receivables				111.0									8.0			8.0		111.0
DESC
Loss Contingencies [Line Items]
Contesting amount for filed liens in Fairfield country									$ 285.0
DESC | SCDOR
Loss Contingencies [Line Items]
Proposed assessment amount from audit										$ 410.0
Proportional share of NND project										100.00%
DESC | SOUTH CAROLINA
Loss Contingencies [Line Items]
Amount claimed by plaintiffs in legal matter								$ 100.0
Percentage claimed by plaintiffs in legal matter								100.00%
SCANA and DESC
Loss Contingencies [Line Items]
Disgorgement and prejudgment interest total, amount		$ 112.5
Minimum | SCANA | DESC Ratepayer Case
Loss Contingencies [Line Items]
Proceeds from sale of property																				60.0
Maximum | SCANA | Common Stock
Loss Contingencies [Line Items]
Litigation settlement amount through stock issuance				32.5
Maximum | SCANA | DESC Ratepayer Case
Loss Contingencies [Line Items]
Proceeds from sale of property																				$ 85.0
Virginia Electric and Power Company
Loss Contingencies [Line Items]
Impairment of assets and other charges													44.0		$ 197.0	808.0	$ 743.0
Property, plant and equipment, net				$ 32,882.0	[2]								$ 31,499.0			$ 31,499.0		32,882.0	[2]
DESC | NND Project Costs
Loss Contingencies [Line Items]
Percentage ownership in total units													55.00%			55.00%
Unfavorable Regulatory Action | VDEQ
Loss Contingencies [Line Items]
Significant emission rate initial carbon cap | T							28,000,000.0
Significant emission rate carbon cap reduction percentage per year							3.00%
Significant emission rate ultimate carbon cap | T							19,600,000
Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Electric generating station facilities heightened entrainment analysis per day | gal																125,000,000
Carbon Regulations
Loss Contingencies [Line Items]
Significant emission rate per rear CO2 equivalent | T												75,000
CWA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Number of mandatory facility-specific factors | Indicator																5
Number of optional facility-specific factors | Indicator																6
Number of facilities that are subject to final regulations | Facility																13
CWA | Unfavorable Regulatory Action | Minimum
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals per day | gal																2,000,000
CWA | Unfavorable Regulatory Action | Virginia Electric and Power Company
Loss Contingencies [Line Items]
Number of facilities that are subject to final regulations | Facility																7
CWA | Unfavorable Regulatory Action | EPA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Number of separate petitions for reconsideration granted | Petition											2
Waste Management and Remediation | Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Number of sites remediation work substantially completed | site																11
Number of sites with remediation plans | site																3
Number of sites with an updated work plan | site																1
Updated work plan, cost increase																$ 11.0
Number of additional sites which are not under investigation | site																13
Waste Management and Remediation | Unfavorable Regulatory Action | EPA | Former Gas Plant Site With Post Closure Groundwater Monitoring Program
Loss Contingencies [Line Items]
Environmental remediation reserves																$ 34.0		34.0
Waste Management and Remediation | Unfavorable Regulatory Action | EPA | Virginia Electric and Power Company
Loss Contingencies [Line Items]
Number of sites with remediation plans | site																1
Number of additional sites which are not under investigation | site																2
Waste Management and Remediation | Unfavorable Regulatory Action | EPA | Virginia Electric and Power Company | Former Gas Plant Site With Post Closure Groundwater Monitoring Program
Loss Contingencies [Line Items]
Environmental remediation reserves																$ 16.0		$ 16.0

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.