Commitments and Contingencies (Narrative) (Detail) $ in Millions	1 Months Ended													3 Months Ended		12 Months Ended
	Dec. 31, 2020 USD ($)		Oct. 31, 2020	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	Jul. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Aug. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Aug. 31, 2017 USD ($)	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2021 USD ($) Indicator Facility site gal	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)		Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Property, plant and equipment, net	$ 57,848.0	[1]												$ 58,421.0		$ 57,848.0	[1]
Common Stock
Loss Contingencies [Line Items]
Litigation settlement, benefit fund						$ 320.0
Litigation settlement amount through stock issuance				$ 322.0
DESC Ratepayer Case
Loss Contingencies [Line Items]
Litigation settlement, benefit fund						$ 520.0
SCANA
Loss Contingencies [Line Items]
Other expense														60.0	$ 25.0
Other expense, after tax														45.0	25.0
Escrow account															$ 160.0
Litigation settlement, amount received from SCANA					$ 32.5		$ 192.5
Litigation settlement paid	25.0
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
Proceeds from sale of property				38.5
Property, plant and equipment, net				$ 3.0	$ 27.0
SCANA | Other Current Liabilities
Loss Contingencies [Line Items]
Reserves for SCANA legal proceedings	208.0													268.0		208.0
SCANA | Other Receivables
Loss Contingencies [Line Items]
Insurance receivables	8.0													8.0		8.0
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]
Property, plant and equipment, net	32,569.0	[2]												$ 32,985.0		32,569.0	[2]
Dominion Energy South Carolina Inc | NND Project
Loss Contingencies [Line Items]
Percentage ownership in total units														55.00%
Contesting amount for filed liens in Fairfield country									$ 285.0
Dominion Energy South Carolina Inc | SCDOR
Loss Contingencies [Line Items]
Proposed assessment amount from audit										$ 410.0
Proportional share of NND project										100.00%
Litigation settlement paid	$ 165.0
Dominion Energy South Carolina Inc | SOUTH CAROLINA
Loss Contingencies [Line Items]
Amount claimed by plaintiffs in legal matter											$ 100.0
Percentage claimed by plaintiffs in legal matter											100.00%
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]
Public Utilities Significant Emission Rate Per Year 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														15
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 | 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
CWA | Unfavorable Regulatory Action | EPA | Minimum | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual circumstances period			2021
CWA | Unfavorable Regulatory Action | EPA | Maximum | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual circumstances period			2028
CWA | Unfavorable Regulatory Action | Virginia Electric and Power Company
Loss Contingencies [Line Items]
Number of facilities that are subject to final regulations | Facility														9
Waste Management and Remediation | Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Number of sites remediation work substantially completed | site														12
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														12
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														$ 40.0		42.0
Waste Management and Remediation | Unfavorable Regulatory Action | Virginia Electric and Power Company | EPA
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 | Virginia Electric and Power Company | EPA | Former Gas Plant Site With Post Closure Groundwater Monitoring Program
Loss Contingencies [Line Items]
Environmental remediation reserves														$ 25.0		$ 26.0

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.