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Employee Future Benefits - Additional Information (Detail) - CAD ($)
$ in Millions
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Disclosure of defined benefit plans [Line Items]    
Assets set aside for plan $ 0  
Canadian plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2023 $ 3  
Return-seeking assets [Member]    
Disclosure of defined benefit plans [Line Items]    
Target asset allocation for plan 30.00% 30.00%
Return-seeking assets [Member] | Canada [member]    
Disclosure of defined benefit plans [Line Items]    
Target asset allocation for plan 20.00% 20.00%
Liability-hedging assets [Member]    
Disclosure of defined benefit plans [Line Items]    
Target asset allocation for plan 70.00% 70.00%
Liability-hedging assets [Member] | Canada [member]    
Disclosure of defined benefit plans [Line Items]    
Target asset allocation for plan 80.00% 80.00%
Pension defined benefit plans [member]    
Disclosure of defined benefit plans [Line Items]    
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2023 $ 65  
Defined contribution pension plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2023 89  
Retiree welfare plans [Member]    
Disclosure of defined benefit plans [Line Items]    
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2023 $ 13