v3.25.4
Post-employment benefit plans - Funded Status of Post-Employment Benefit Plans Cost (Details) - CAD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of defined benefit plans [line items]    
Post-employment benefit asset (liability) $ (3,159) $ (2,374)
Plan asset (deficit)    
Disclosure of defined benefit plans [line items]    
Post-employment benefit asset (liability) (4,224) (3,370)
Plan asset (deficit) | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Present value of post-employment benefit obligations (20,573) (21,188)
Fair value of plan assets 24,797 24,558
Plan surplus (deficit) 4,224 3,370
Post-employment benefit asset (liability) 3,159 2,374
Plan asset (deficit) | Funded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Present value of post-employment benefit obligations (18,981) (19,558)
Fair value of plan assets 24,355 24,123
Plan surplus (deficit) 5,374 4,565
Post-employment benefit asset (liability) 4,309 3,569
Plan asset (deficit) | Partially funded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Present value of post-employment benefit obligations (1,347) (1,425)
Fair value of plan assets 442 435
Plan surplus (deficit) (905) (990)
Post-employment benefit asset (liability) (905) (990)
Plan asset (deficit) | Unfunded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Present value of post-employment benefit obligations (245) (205)
Fair value of plan assets 0 0
Plan surplus (deficit) (245) (205)
Post-employment benefit asset (liability) (245) (205)
Effect of asset limit    
Disclosure of defined benefit plans [line items]    
Post-employment benefit asset (liability) 1,018 960
Effect of asset limit | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Effect and interest of asset limit (1,065) (996)
Effect of asset limit | Funded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Effect and interest of asset limit (1,065) (996)
Effect of asset limit | Partially funded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Effect and interest of asset limit 0 0
Effect of asset limit | Unfunded | Defined Benefit Plan and OPEB    
Disclosure of defined benefit plans [line items]    
Effect and interest of asset limit $ 0 $ 0