v3.25.4
Employee Future Benefits - Components of Net Benefit Cost for Pension Plans and Retiree Welfare Plans (Detail) - Net Benefit Cost Recognized in the Consolidated Statements of Income - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Pension plans    
Disclosure of defined benefit plans [line items]    
Defined benefit current service cost $ 44 $ 44
Defined benefit administrative expenses 10 8
Past service cost – plan amendments and curtailments 0 0
Service cost 54 52
Interest on net defined benefit (asset) liability (1) 4
Defined benefit cost 53 56
Defined contribution cost 101 97
Net benefit cost 154 153
Retiree welfare plans    
Disclosure of defined benefit plans [line items]    
Defined benefit current service cost 0 0
Defined benefit administrative expenses 2 2
Past service cost – plan amendments and curtailments 0 0
Service cost 2 2
Interest on net defined benefit (asset) liability (8) (5)
Defined benefit cost (6) (3)
Defined contribution cost 0 0
Net benefit cost $ (6) $ (3)