v3.25.2
Retirement benefits - Summary of Retirement Benefit Expense (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Defined benefit plans:      
Interest income on plan assets $ (3,417) $ (1,732) $ (1,160)
Other 262 246 (343)
Total 850 1,375 1,293
Defined contribution plans 474 420 403
Total retirement benefit expense 1,324 1,795 1,696
Pensions      
Defined benefit plans:      
Current service cost, defined benefit plans 731 1,100 1,385
Interest expense, defined benefit plans 3,072 1,584 1,223
OPEB      
Defined benefit plans:      
Current service cost, defined benefit plans 36 57 60
Interest expense, defined benefit plans $ 166 $ 120 $ 128