v3.25.4
POST-EMPLOYMENT BENEFITS - Summary of Accrued Benefit Obligations (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Changes in net defined benefit liability (asset) [abstract]    
Accrued benefit obligations, beginning of year $ 93  
Contributions by employees 25 $ 25
Accrued benefit obligations, end of year 93 93
Domestic defined benefit plans    
Changes in net defined benefit liability (asset) [abstract]    
Accrued benefit obligations, beginning of year (175)  
Current service cost 74 86
Past service cost 13 0
Pension expense, recognized in employee salaries and benefits expense (80) (81)
Net interest cost, recognized in finance costs (10) (8)
Remeasurements, recognized in other comprehensive income and equity (112) (176)
Accrued benefit obligations, end of year (212) (175)
Domestic defined benefit plans | Accrued benefit obligation    
Changes in net defined benefit liability (asset) [abstract]    
Accrued benefit obligations, beginning of year 2,197 2,260
Current service cost 74 86
Past service cost 13 0
Net interest cost, recognized in finance costs 107 102
Benefits paid (41) (51)
Impact of annuitization 0 (140)
Contributions by employees 25 25
Remeasurements, recognized in other comprehensive income and equity (126) (85)
Accrued benefit obligations, end of year 2,249 2,197
Unfunded supplemental benefits for certain executives | Accrued benefit obligation    
Changes in net defined benefit liability (asset) [abstract]    
Accrued benefit obligations, beginning of year 93 94
Pension expense, recognized in employee salaries and benefits expense 3 4
Net interest cost, recognized in finance costs 5 3
Benefits paid (5) (7)
Remeasurements, recognized in other comprehensive income and equity (3) (1)
Accrued benefit obligations, end of year $ 93 $ 93