Commitments and Contingencies (Narrative) (Detail) shares in Millions, $ in Millions		1 Months Ended								3 Months Ended		12 Months Ended
	May 05, 2022 shares	Aug. 31, 2021 shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 31, 2020	Jun. 30, 2018 USD ($)	Aug. 31, 2017 USD ($)	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2022 USD ($) site	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) Indicator Facility gal	Dec. 31, 2021 USD ($)
SCANA
Loss Contingencies [Line Items]
Impairment of assets and other charges										$ 0	$ 60
Impairment of assets and other charges, after tax											$ 45
SCANA | State Court Derivative Case
Loss Contingencies [Line Items]
Litigation settlement paid			$ 33
SCANA | Federal Court Merger Case | State Court Merger Case
Loss Contingencies [Line Items]
Litigation settlement paid			63
SCANA | Other Current Liabilities
Loss Contingencies [Line Items]
Reserves for SCANA legal proceedings										257		$ 257	$ 274
SCANA | Other Receivables
Loss Contingencies [Line Items]
Insurance receivables										118		$ 118	118
Virginia Electric and Power Company | EPA and State Regulatory Agencies
Loss Contingencies [Line Items]
Number of facilities to assess the applicability of section 316(b) | Facility												3
Hydroelectric Facilities | EPA and State Regulatory Agencies
Loss Contingencies [Line Items]
Number of facilities to assess the applicability of section 316(b) | Facility												8
Dominion Energy South Carolina Inc | SCDOR
Loss Contingencies [Line Items]
Litigation settlement paid				$ 165
Proposed assessment amount from audit						$ 410
Proportional share of NND project						100.00%
Dominion Energy South Carolina Inc | South Carolina
Loss Contingencies [Line Items]
Amount claimed by plaintiffs in legal matter							$ 100
Percentage claimed by plaintiffs in legal matter							100.00%
Dominion Energy South Carolina Inc | DESC | SCDOR | Common Stock
Loss Contingencies [Line Items]
Initial litigation settlement through stock issuance | shares		0.6
Dominion Energy South Carolina Inc | DESC | SCDOR | Subsequent Event | Common Stock
Loss Contingencies [Line Items]
Initial litigation settlement through stock issuance | shares	0.9
Dominion Energy South Carolina Inc | Minimum [Member] | SCDOR
Loss Contingencies [Line Items]
Initial litigation settlement amount through stock issuance			$ 43
Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Electric generating station facilities heightened entrainment analysis per day | gal												125,000,000
Personal Injury or Wrong Death Cases | SCANA
Loss Contingencies [Line Items]
Reserves for SCANA legal proceedings										70		$ 70	85
Insurance receivables										$ 70		$ 70	85
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 [Member]
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 [Member] | 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										13
Number of sites with remediation plans | site										2
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										$ 52			45
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			$ 25