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Income Taxes - Additional Information (Detail) - CAD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Disclosure of Income Taxes [line items]    
Unrecognized deferred tax assets $ 293 $ 296
Unrecognized deferred tax liabilities 803 731
Canada    
Disclosure of Income Taxes [line items]    
Unused tax losses 1,160 3,810
Chile    
Disclosure of Income Taxes [line items]    
Unused tax losses $ 972 $ 847
Antamina    
Disclosure of Income Taxes [line items]    
Proportion of ownership interest in joint operation 22.50%