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Commitments and Contingencies (Narrative) (Detail)
shares in Millions
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
May 31, 2024
Mar. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
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, 2024
USD ($)
Sep. 30, 2023
USD ($)
Mar. 31, 2023
USD ($)
Sep. 30, 2024
USD ($)
Indicator
Site
Facility
gal
Sep. 30, 2023
USD ($)
Dec. 31, 2023
USD ($)
Jun. 30, 2023
USD ($)
Dec. 31, 2022
USD ($)
Loss Contingencies [Line Items]                                            
Gain on sales of assets                             $ 0 $ 0   $ 2,000,000 $ 23,000,000      
Gain on sales of assets after tax                             $ 967,000,000 $ 698,000,000   $ 2,018,000,000 1,813,000,000      
Nuclear Obligations | Secondary Financial Protection Program                                            
Loss Contingencies [Line Items]                                            
Maximum liability protection per nuclear incident amount   $ 16,300,000,000 $ 16,200,000,000                                      
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           $ 51,000,000       $ 165,000,000                        
Proposed assessment amount from audit                       $ 410,000,000                    
Proportional share of NND project                       100.00%                    
Fair value of certain non-utility property transferred         $ 28,000,000                                  
Fair value of utility property transferred                                 $ 10,000,000          
Gain upon completion of remaining transfer of utility properties                                         $ 11,000,000  
Fair value of additional utility property transferred                                           $ 3,000,000
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                                     9,000,000      
Gain on sales of assets after tax                                     7,000,000      
Dominion Energy South Carolina Inc | Remaining Utility Property Transferred | SCDOR                                            
Loss Contingencies [Line Items]                                            
Gain on sales of assets                                     11,000,000      
Gain on sales of assets after tax                                     $ 8,000,000      
Dominion Energy South Carolina Inc | Minimum | SCDOR                                            
Loss Contingencies [Line Items]                                            
Initial litigation settlement amount through stock issuance                 $ 43,000,000                          
Dominion Energy South Carolina Inc | Maximum | SCDOR                                            
Loss Contingencies [Line Items]                                            
Cash payment for remaining obligation       $ 1,000,000                                    
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        
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                                   14        
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                  
Loss contingencies facility retirement period 2034                                          
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 2029                   2028                      
CWA | Unfavorable Regulatory Action | Virginia Electric and Power Company                                            
Loss Contingencies [Line Items]                                            
Number of facilities that are subject to final regulations | Facility                                   8        
Waste Management and Remediation | Unfavorable Regulatory Action | EPA                                            
Loss Contingencies [Line Items]                                            
Number of sites remediation work substantially completed | Site                                   4        
Number of additional sites which are not under investigation | Site                                   3        
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                                   $ 31,000,000   $ 32,000,000    
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                                   $ 25,000,000   25,000,000    
Millstone, Summer, Surry and North Anna                                            
Loss Contingencies [Line Items]                                            
Amount of coverage purchased from commercial insurance pools   $ 500,000,000 $ 450,000,000                                 $ 450,000,000