v3.26.1
Retirement Benefits - Net Benefit Costs (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Defined Contribution Plan Disclosure [Line Items]    
Service cost $ 27 $ 25
Interest cost 119 121
Expected return on assets (127) (130)
Prior service (credit) cost (1) (2)
Actuarial (gain) loss 37 24
Non-service components of pension benefits & OPEB (credit) cost 28 13
Net periodic benefit cost 55 38
Pension Benefits    
Defined Contribution Plan Disclosure [Line Items]    
Service cost 22 21
Interest cost 99 102
Expected return on assets (119) (122)
Prior service (credit) cost 0 0
Actuarial (gain) loss 38 26
Non-service components of pension benefits & OPEB (credit) cost 18 6
Net periodic benefit cost 40 27
OPEB    
Defined Contribution Plan Disclosure [Line Items]    
Service cost 5 4
Interest cost 20 19
Expected return on assets (8) (8)
Prior service (credit) cost (1) (2)
Actuarial (gain) loss (1) (2)
Non-service components of pension benefits & OPEB (credit) cost 10 7
Net periodic benefit cost $ 15 $ 11