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Post-retirement benefits - Results summary of sensitivity analysis (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
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 $ 483 $ 854
Decrease of actuarial assumption $ (510) $ (915)
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 $ 32 $ 51
Decrease of actuarial assumption $ (34) $ (55)
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 $ (174) $ (393)
Decrease of actuarial assumption $ 168 $ 374
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 $ (10) $ (14)
Decrease of actuarial assumption $ 9 $ 13
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 $ 241 $ 441
Decrease of actuarial assumption $ (241) $ (441)
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 $ 8 $ 15
Decrease of actuarial assumption $ (8) $ (15)