v3.26.3
Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Amortization of:        
Non-service net periodic benefit cost $ (12) $ (13) $ (33) $ (39)
Pension Plan, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 40 38 120 115
Interest cost 143 146 428 439
Expected return on assets (176) (179) (528) (535)
Amortization of:        
Prior service cost (credit) 1 1 2 2
Actuarial loss (gain) 51 53 151 159
Non-service net periodic benefit cost 59 59 173 180
Other Postretirement Benefit Plan, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 6 7 20 19
Interest cost 25 26 75 76
Expected return on assets (21) (21) (64) (63)
Amortization of:        
Prior service cost (credit) (2) (2) (6) (6)
Actuarial loss (gain) 0 (1) (1) (2)
Non-service net periodic benefit cost $ 8 $ 9 $ 24 $ 24