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Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Mar. 31, 2024
Sep. 30, 2025
Sep. 30, 2024
Segment Reporting Information [Line Items]      
Gain (loss) on investments   $ 442 $ 589
Charge in connection with settlement of an agreement $ 47    
Charge in connection with settlement of an agreement, after tax $ 35    
Operating Segments      
Segment Reporting Information [Line Items]      
After- tax net benefits (expenses)   81 76
Gain (loss) on investments   415 515
Gain (loss) on investments, after tax   255 $ 323
Investment, Type [Extensible Enumeration]     Nuclear Decommissioning Trust Fund [Member]
Corporate and Other | Operating Segments      
Segment Reporting Information [Line Items]      
After- tax net benefits (expenses)   (108) $ (272)
After-tax net income for specific items   58 12
Contracted Energy | Operating Segments      
Segment Reporting Information [Line Items]      
Gain (loss) on investments, after tax   221 278
Gain (loss) related to economic hedging activities   (16) (107)
Gain (loss) related to economic hedging activities after tax   (12) (82)
Charge in connection with settlement of an agreement     47
Charge in connection with settlement of an agreement, after tax     35
Charge for impairment of nonregulated renewable natural gas facilities     60
Charge for impairment of nonregulated renewable natural gas facilities after tax     46
Dominion Energy Virginia | Operating Segments      
Segment Reporting Information [Line Items]      
Gain (loss) on investments, after tax   $ 34 $ 45
Investment, Type [Extensible Enumeration]   Nuclear Decommissioning Trust Fund [Member] Nuclear Decommissioning Trust Fund [Member]
Share of costs not expected to be recovered from customers on the CVOW commercial project   $ 112  
Share of costs not expected to be recovered from customers on the CVOW commercial project, after tax   84  
Loss associated with severe weather events   106  
Loss associated with severe weather events, after-tax   $ 79  
Charge related to write-off of certain early stage development costs     $ 30
Charge related to write-off of certain early stage development costs after tax     22
Dominion Energy South Carolina | Operating Segments      
Segment Reporting Information [Line Items]      
Charge in connection with the electric base rate case     58
Charge in connection with the electric base rate case, after tax     $ 44