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Employee Future Benefits - Summary of Weighted Average Duration of the Defined Benefit Obligations (Detail) - yr
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Pension defined benefit plans [member] | U.S. plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Weighted average duration (in years) of the defined benefit obligations 9.7 9.9
Pension defined benefit plans [member] | Canadian plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Weighted average duration (in years) of the defined benefit obligations 12.4 12.5
Retiree welfare plans [Member] | U.S. plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Weighted average duration (in years) of the defined benefit obligations 9.5 9.8
Retiree welfare plans [Member] | Canadian plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Weighted average duration (in years) of the defined benefit obligations 13.3 14.3