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Commitments and Contingencies (Narrative) (Detail)
shares in Millions, $ in Millions
 1 Months Ended 3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Jul. 31, 2023
USD ($)
Sep. 30, 2022
USD ($)
Jun. 30, 2022
USD ($)
May 31, 2022
shares
Aug. 31, 2021
shares
Jun. 30, 2021
USD ($)
Dec. 31, 2020
USD ($)
Oct. 31, 2020
Jun. 30, 2018
USD ($)
Apr. 30, 2017
Petition
Aug. 31, 2016
T
Sep. 30, 2023
USD ($)
Mar. 31, 2023
USD ($)
Sep. 30, 2022
USD ($)
Jun. 30, 2022
Site
Jun. 30, 2023
USD ($)
gal
Sep. 30, 2023
USD ($)
Site
Indicator
Facility
gal
Sep. 30, 2022
USD ($)
Dec. 31, 2022
USD ($)
Loss Contingencies [Line Items]                                      
Gain on sales of assets                       $ 0   $ 27     $ 23 $ (581)  
Gain on sales of assets after tax                       717   $ 626     1,864 $ 261  
SCANA | Other Current Liabilities                                      
Loss Contingencies [Line Items]                                      
Reserves for SCANA legal proceedings                       3         3   $ 94
SCANA | Other Receivables                                      
Loss Contingencies [Line Items]                                      
Insurance receivables                       $ 26         $ 26   68
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     $ 51       $ 165                        
Proposed assessment amount from audit                 $ 410                    
Proportional share of NND project                 100.00%                    
Fair value of certain non-utility property transferred   $ 28                                  
Fair value of utility property transferred                         $ 10            
Gain upon completion of remaining transfer of utility properties                               $ 11      
Fair value of additional utility property transferred                                     3
Dominion Energy South Carolina Inc | DESC | SCDOR | Common Stock                                      
Loss Contingencies [Line Items]                                      
Initial litigation settlement through stock issuance | shares       0.9 0.6                            
Dominion Energy South Carolina Inc | Utility Property Transferred | SCDOR                                      
Loss Contingencies [Line Items]                                      
Gain on sales of assets                                 $ 9    
Gain on sales of assets after tax                                 7    
Dominion Energy South Carolina Inc | Remaining Utility Property Transferred | SCDOR                                      
Loss Contingencies [Line Items]                                      
Gain on sales of assets                                 11    
Gain on sales of assets after tax                                 $ 8    
Dominion Energy South Carolina Inc | Minimum | SCDOR                                      
Loss Contingencies [Line Items]                                      
Initial litigation settlement amount through stock issuance           $ 43                          
Dominion Energy South Carolina Inc | Maximum | SCDOR                                      
Loss Contingencies [Line Items]                                      
Cash payment for remaining obligation $ 1                                    
Unfavorable Regulatory Action | EPA                                      
Loss Contingencies [Line Items]                                      
Electric generating station facilities water withdrawals per day | gal                                 2,000,000    
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                                     68
Insurance receivables                                     68
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                             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                                 $ 42   47
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