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Commitments and Contingencies (Narrative) (Detail)
shares in Millions, $ in Millions
 1 Months Ended 12 Months Ended
Aug. 31, 2021
shares
Jul. 31, 2021
USD ($)
shares
Jun. 30, 2021
USD ($)
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 ($)
Apr. 30, 2017
Petition
Aug. 31, 2016
T
Dec. 31, 2021
USD ($)
Facility
Indicator
site
gal
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Mar. 31, 2020
USD ($)
Loss Contingencies [Line Items]                                        
Impairment of assets and other charges                               $ 195.0 $ 2,105.0 $ 1,520.0    
Property, plant and equipment, net       $ 57,848.0                       59,774.0 57,848.0      
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                                 25.0      
Other expense, after tax                                 25.0      
Impairment of assets and other charges                               100.0 90.0 641.0    
Impairment of assets and other charges, after tax                               75.0 68.0 $ 480.0    
Escrow account                                       $ 160.0
Litigation settlement expense             $ 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                 8.0        
SCANA | State Court Derivative Case                                        
Loss Contingencies [Line Items]                                        
Litigation settlement paid     $ 33.0                                  
SCANA | Federal Court Merger Case | State Court Merger Case                                        
Loss Contingencies [Line Items]                                        
Litigation settlement paid     63.0                                  
SCANA | Other Current Liabilities                                        
Loss Contingencies [Line Items]                                        
Reserves for SCANA legal proceedings       208.0                       274.0 208.0      
SCANA | Other Receivables                                        
Loss Contingencies [Line Items]                                        
Insurance receivables       8.0                       118.0 8.0      
DESC                                        
Loss Contingencies [Line Items]                                        
Litigation settlement expense   $ 99.0                                    
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                       $ 34,656.0 32,569.0      
Virginia Electric and Power Company | Environmental Protection Agency And State Regulatory Agencies                                        
Loss Contingencies [Line Items]                                        
Number of facilities to assess the applicability of section 316(b) | Facility                               3        
Hydroelectric Facilities | Environmental Protection Agency 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 | NND Project                                        
Loss Contingencies [Line Items]                                        
Noncontrolling partnership interest                               55.00%        
Contested amount for filed liens in Fairfield country                     $ 285.0                  
Dominion Energy South Carolina Inc | SCDOR                                        
Loss Contingencies [Line Items]                                        
Litigation settlement paid       165.0                                
Proposed assessment amount from audit                       $ 410.0                
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                         $ 100.0              
Percentage claimed by plaintiffs in legal matter                         100.00%              
Dominion Energy South Carolina Inc | DESC | Common Stock                                        
Loss Contingencies [Line Items]                                        
Litigation settlement through stock issuance | shares   1.4                                    
Dominion Energy South Carolina Inc | DESC | Common Stock | SCDOR                                        
Loss Contingencies [Line Items]                                        
Initial litigation settlement through stock issuance | shares 0.6                                      
Dominion Energy South Carolina Inc | Minimum | SCDOR                                        
Loss Contingencies [Line Items]                                        
Initial litigation settlement amount through stock issuance     $ 43.0                                  
Unfavorable Regulatory Action | EPA                                        
Loss Contingencies [Line Items]                                        
Electric generating station facilities heightened entrainment analysis per day | gal                               125,000,000        
Personal Injury or Wrongful Death Cases | SCANA                                        
Loss Contingencies [Line Items]                                        
Reserves for SCANA legal proceedings       8.0                       $ 85.0 8.0      
Insurance receivables       $ 8.0                       $ 85.0 8.0      
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                               13        
Number of sites with remediation plans | site                               2        
Environmental remediation reserves                               $ 11.0        
Environmental remediation expense                                 14.0      
Environmental remediation expense net of tax                                 11.0      
Number of sites with an updated work plan | site                               1        
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                               $ 45.0 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        
Environmental remediation expense                                 10.0      
Environmental remediation expense net of tax                                 7.0      
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