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Post-retirement benefits - Results summary of sensitivity analysis (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Discount rate | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of percentage points 50.00% 50.00%
Decrease of percentage points 50.00% 50.00%
Increase of actuarial assumption $ 460 $ 483
Decrease of actuarial assumption $ (514) $ (510)
Discount rate | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of percentage points 50.00% 50.00%
Decrease of percentage points 50.00% 50.00%
Increase of actuarial assumption $ 31 $ 32
Decrease of actuarial assumption $ (33) $ (34)
Long-term inflation | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of percentage points 50.00% 50.00%
Decrease of percentage points 50.00% 50.00%
Increase of actuarial assumption $ (183) $ (174)
Decrease of actuarial assumption $ 176 $ 168
Long-term inflation | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of percentage points 50.00% 50.00%
Decrease of percentage points 50.00% 50.00%
Increase of actuarial assumption $ (9) $ (10)
Decrease of actuarial assumption $ 8 $ 9
Demographic – allowance for future improvements in longevity | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase in actuarial assumption of longevity trend 1 year 1 year
Decrease in actuarial assumption of longevity trend 1 year 1 year
Increase of actuarial assumption $ 244 $ 241
Decrease of actuarial assumption $ (244) $ (241)
Demographic – allowance for future improvements in longevity | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase in actuarial assumption of longevity trend 1 year 1 year
Decrease in actuarial assumption of longevity trend 1 year 1 year
Increase of actuarial assumption $ 7 $ 8
Decrease of actuarial assumption $ (7) $ (8)