v3.25.4
POST-EMPLOYMENT BENEFITS - Summary of Pension Fund Assets (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Changes in net defined benefit liability (asset) [abstract]    
Plan assets, beginning of year $ (93)  
Remeasurements, recognized in other comprehensive income and equity 140 $ 209
Contributions by employees 25 25
Contributions by employer 0 5
Plan assets, end of year (93) (93)
Domestic defined benefit plans    
Changes in net defined benefit liability (asset) [abstract]    
Plan assets, beginning of year 175  
Interest income 10 8
Remeasurements, recognized in other comprehensive income and equity 26 101
Administrative expenses paid from plan assets (3) (3)
Plan assets, end of year 212 175
Domestic defined benefit plans | Plan assets    
Changes in net defined benefit liability (asset) [abstract]    
Plan assets, beginning of year 2,385 2,339
Interest income 117 110
Remeasurements, recognized in other comprehensive income and equity 26 101
Contributions by employees 25 25
Contributions by employer 0 5
Benefits paid (41) (51)
Impact of annuitization 0 (141)
Plan assets acquired in MLSE Transaction 5 0
Administrative expenses paid from plan assets (3) (3)
Plan assets, end of year $ 2,514 $ 2,385