XML 721 R241.htm IDEA: XBRL DOCUMENT v3.20.4
Post-retirement benefits - Results summary of sensitivity analysis (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Discount rate | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ 988 $ 894
Decrease of actuarial assumption $ (1,186) $ (1,057)
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Discount rate | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ 62 $ 56
Decrease of actuarial assumption $ (66) $ (60)
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Inflation | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ (484) $ (447)
Decrease of actuarial assumption $ 450 $ 422
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Inflation | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ (19) $ (17)
Decrease of actuarial assumption $ 17 $ 15
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Salary increases | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ (81) $ (55)
Decrease of actuarial assumption $ 72 $ 54
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Salary increases | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ (1) $ (1)
Decrease of actuarial assumption $ 1 $ 1
Increase of percentage points 0.50% 0.50%
Decrease of percentage points 0.50% 0.50%
Demographic – allowance for future improvements in longevity | Pension benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ 520 $ 443
Decrease of actuarial assumption $ (562) $ (465)
Increase in actuarial assumption of longevity trend 1 year 1 year
Decrease in actuarial assumption of longevity trend 1 year 1 year
Demographic – allowance for future improvements in longevity | Other benefits    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Increase of actuarial assumption $ 19 $ 18
Decrease of actuarial assumption $ (19) $ (18)
Increase in actuarial assumption of longevity trend 1 year 1 year
Decrease in actuarial assumption of longevity trend 1 year 1 year