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Employee Benefit Plans (Net Periodic Benefit (Credit) Cost and Amounts Recognized in Other Comprehensive Income and Regulatory Assets and Liabilities) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension Benefits      
Service cost $ 83 $ 96 $ 142
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Other Nonoperating Income (Expense) Other Nonoperating Income (Expense) Other Nonoperating Income (Expense)
Interest cost $ 431 $ 442 $ 333
Expected return on plan assets (811) (864) (886)
Amortization of prior service (credit) cost 1    
Net actuarial (gain) loss (96) 304 726
Settlements, curtailments and special termination benefits [1] (56)   (3)
Plan amendment 22    
Net periodic benefit (credit) cost (426) (22) 312
Changes in plan assets and benefit obligations recognized in [other comprehensive income] and regulatory assets and liabilities:      
Prior service (credit) cost 6 2 1
Amortization of prior service credit (cost) (1)    
Total recognized in other comprehensive income and regulatory assets and liabilities $ 5 $ 2 $ 1
Significant assumptions used to determine periodic cost:      
Weighted average rate of increase for compensation 4.28% 4.38% 4.51%
Pension Benefits | Minimum      
Significant assumptions used to determine periodic cost:      
Discount rate 5.37% 5.65% 3.06%
Expected long-term rate of return on plan assets 7.00% 7.00% 7.00%
Crediting interest rate for cash balance and similar plans 4.12% 4.40% 1.81%
Pension Benefits | Maximum      
Significant assumptions used to determine periodic cost:      
Discount rate 5.75% 5.75% 3.19%
Expected long-term rate of return on plan assets 8.35% 8.35% 8.35%
Crediting interest rate for cash balance and similar plans 4.50% 4.50% 1.94%
Other Postretirement Benefits      
Service cost $ 11 $ 14 $ 22
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Other Nonoperating Income (Expense) Other Nonoperating Income (Expense) Other Nonoperating Income (Expense)
Interest cost $ 57 $ 61 $ 45
Expected return on plan assets (171) (151) (191)
Amortization of prior service (credit) cost (36) (36) (38)
Net actuarial (gain) loss (107) (125) 246
Settlements, curtailments and special termination benefits [1] (4)   (8)
Net periodic benefit (credit) cost (250) (237) 76
Changes in plan assets and benefit obligations recognized in [other comprehensive income] and regulatory assets and liabilities:      
Prior service (credit) cost 4   8
Amortization of prior service credit (cost) 36 36 38
Total recognized in other comprehensive income and regulatory assets and liabilities $ 40 $ 36 $ 46
Significant assumptions used to determine periodic cost:      
Expected long-term rate of return on plan assets 8.35% 8.35% 8.35%
Health care cost trend rate [2] 7.00% 7.00% 6.25%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) [2] 5.00% 5.00% 5.00%
Year that the rate reaches the ultimate trend rate [2] 2031 2030  
Other Postretirement Benefits | Minimum      
Significant assumptions used to determine periodic cost:      
Discount rate 5.40% 5.69% 3.04%
Year that the rate reaches the ultimate trend rate [2]     2026
Other Postretirement Benefits | Maximum      
Significant assumptions used to determine periodic cost:      
Discount rate 5.74% 5.70% 5.03%
Year that the rate reaches the ultimate trend rate [2]     2027
[1] 2024 amounts relate primarily to the East Ohio Transaction. 2022 amounts relate primarily to Dominion Energy’s sale of Hope.
[2] Assumptions used to determine net periodic cost for the following year.