v3.25.4
Post-employment benefit plans - Components of Post-Employment Benefit (Obligations) Assets (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 $ 2,374  
Interest on obligations 102 $ 66
Actuarial gains 881 984
Post-employment benefit obligations, December 31 3,159 2,374
Post-employment benefit assets 4,310 3,578
Post-employment benefit obligations (1,151) (1,204)
Experience gains included in actuarial gains 391 809
Actual return on plan assets $ 1,529 $ 1,848
Actual return on plan assets, percent 6.40% 8.10%
Benefit obligations    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 $ (21,188) $ (21,669)
Current service cost (126) (135)
Interest on obligations (972) (976)
Actuarial gains 473 214
Benefit payments 1,473 1,419
Employee contributions (7) (8)
Business combinations (224) (33)
Other (2) 0
Post-employment benefit obligations, December 31 (20,573) (21,188)
Plan assets    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 24,558 24,098
Expected return on plan assets 1,121 1,078
Actuarial gains 408 770
Benefit payments (1,473) (1,419)
Employer contributions 109 109
Employee contributions 7 8
Transfers to DC plans (127) (132)
Business combinations 201 47
Refundable tax (6) 0
Other (1) (1)
Post-employment benefit obligations, December 31 24,797 24,558
Plan asset (deficit)    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 3,370  
Post-employment benefit obligations, December 31 4,224 3,370
Effect of asset limit    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (960)  
Interest on obligations (47) (36)
Post-employment benefit obligations, December 31 (1,018) (960)
DB pension plans    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 3,058  
Current service cost (125) (134)
Interest on obligations 133 99
Post-employment benefit obligations, December 31 3,816 3,058
Post-employment benefit assets 4,310 3,578
Post-employment benefit obligations (494) (520)
DB pension plans | Benefit obligations    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (20,134) (20,595)
Current service cost (125) (134)
Interest on obligations (924) (927)
Actuarial gains 437 214
Benefit payments 1,404 1,349
Employee contributions (7) (8)
Business combinations (181) (33)
Other (2) 0
Post-employment benefit obligations, December 31 (19,532) (20,134)
DB pension plans | Plan assets    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 24,188 23,768
Expected return on plan assets 1,104 1,062
Actuarial gains 401 737
Benefit payments (1,404) (1,349)
Employer contributions 50 48
Employee contributions 7 8
Transfers to DC plans (127) (132)
Business combinations 201 47
Refundable tax (6) 0
Other (1) (1)
Post-employment benefit obligations, December 31 24,413 24,188
DB pension plans | Plan asset (deficit)    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 4,054  
Post-employment benefit obligations, December 31 4,881 4,054
DB pension plans | Effect of asset limit    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (960)  
Interest on obligations (47) (36)
Post-employment benefit obligations, December 31 (1,018) (960)
OPEB plans    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (684)  
Current service cost (1) (1)
Interest on obligations (31) (33)
Post-employment benefit obligations, December 31 (657) (684)
Post-employment benefit assets 0 0
Post-employment benefit obligations (657) (684)
OPEB plans | Benefit obligations    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (1,054) (1,074)
Current service cost (1) (1)
Interest on obligations (48) (49)
Actuarial gains 36 0
Benefit payments 69 70
Employee contributions 0 0
Business combinations (43) 0
Other 0 0
Post-employment benefit obligations, December 31 (1,041) (1,054)
OPEB plans | Plan assets    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 370 330
Expected return on plan assets 17 16
Actuarial gains 7 33
Benefit payments (69) (70)
Employer contributions 59 61
Employee contributions 0 0
Transfers to DC plans 0 0
Business combinations 0 0
Refundable tax 0 0
Other 0 0
Post-employment benefit obligations, December 31 384 370
OPEB plans | Plan asset (deficit)    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 (684)  
Post-employment benefit obligations, December 31 (657) (684)
OPEB plans | Effect of asset limit    
Reconciliation of changes in net assets available for benefits [abstract]    
Post-employment benefit obligations, January 1 0  
Interest on obligations 0 0
Post-employment benefit obligations, December 31 $ 0 $ 0