v3.25.4
Employee Future Benefits - Cash Payments (Detail) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Pension plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans $ 156 $ 154
Retiree welfare plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans 13 12
Defined benefit plans | Pension plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans 55 57
Defined benefit plans | Retiree welfare plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans 13 12
Defined contribution plans | Pension plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans 101 97
Defined contribution plans | Retiree welfare plans    
Disclosure of net defined benefit liability (asset) [Line Items]    
Cash payment for future benefit plans $ 0 $ 0