v3.25.2
Retirement benefits - Summary of Retirement Benefit Expense (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined benefit plans:      
Interest income on plan assets $ (2,999) $ (3,417) $ (1,732)
Other (457) 262 246
Total 295 850 1,375
Defined contribution plans 514 474 420
Total retirement benefit expense 809 1,324 1,795
Pensions      
Defined benefit plans:      
Current service cost, net of plan participants' contributions 802 731 1,100
Interest expense on defined pension benefit obligations 2,757 3,072 1,584
OPEB      
Defined benefit plans:      
Current service cost, net of plan participants' contributions 38 36 57
Interest expense on defined pension benefit obligations $ 154 $ 166 $ 120