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Employee Future Benefits - Summary of Potential Impact on Obligations Arising From Changes in Key Assumptions (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2021
U.S. [member]  
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]  
Decrease in mortality rates 10.00%
Male [Member] | U.S. [member]  
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]  
Increase in life expectancy due to decrease in mortality rate 9 months 18 days
Male [Member] | Canada [member]  
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]  
Increase in life expectancy due to decrease in mortality rate 9 months 18 days
Female [Member] | U.S. [member]  
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]  
Increase in life expectancy due to decrease in mortality rate 9 months 18 days
Female [Member] | Canada [member]  
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]  
Increase in life expectancy due to decrease in mortality rate 9 months 18 days