v3.25.1
Pension and Other Postretirement Benefits (OPEB) - Schedule of Components of Net Periodic Benefit Cost (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Pension Benefits [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service Cost (included in O&M Expense) $ 22 $ 23
Interest Cost 58 56
Expected Return on Plan Assets (77) (80)
Amortization of Net Prior Service Credit 0 0
Amortization of Net Actuarial Loss (Gain) 15 18
Non-Service Components of Pension and OPEB (Credits) Costs (4) (6)
Total Net Benefit (Credits) Costs 18 17
OPEB [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service Cost (included in O&M Expense) 0 1
Interest Cost 9 9
Expected Return on Plan Assets (8) (9)
Amortization of Net Prior Service Credit 1 0
Amortization of Net Actuarial Loss (Gain) (1) 0
Non-Service Components of Pension and OPEB (Credits) Costs 1 0
Total Net Benefit (Credits) Costs $ 1 $ 1