v3.26.1
STOCK-BASED COMPENSATION PLANS - Ultimate parent corporation outstanding options (Details) - Ultimate parent corporation stock option plan
$ in Millions
12 Months Ended
Dec. 31, 2025
CAD ($)
Option
$ / shares
Dec. 31, 2024
CAD ($)
Option
$ / shares
STOCK-BASED COMPENSATION PLANS    
Options, balance at beginning of year | Option 3,728,227 2,741,560
Options, granted | Option 1,465,000 1,060,000
Options, transferred | Option   450,000
Options, exercised (704,991) (91,666)
Options, cancelled | Option   (431,667)
Options, balance at end of year | Option 4,488,236 3,728,227
Number of vested options | Option 397,530 559,920
Weighted average exercise price, balance at beginning of year (in CAD per share) $ 31.14 $ 31.43
Weighted average exercise price, granted (in CAD per share) 43.58 29.82
Weighted average exercise price, transferred (in CAD per share)   31.91
Weighted average exercise price, exercised (in CAD per share) 31.52 30.44
Weighted average exercise price, cancelled (in CAD per share)   30.67
Weighted average exercise price, balance at end of year (in CAD per share) 35.14 31.14
Weighted average exercise price, vested options (in CAD per share) $ 32.15 $ 32.01
Cash consideration on stock options exercised | $ $ 5.0 $ 0.3
Weighted average years to maturity 8 years 2 months 12 days  
Bottom of range    
STOCK-BASED COMPENSATION PLANS    
Exercise price (in dollars per share) $ 26.52  
Top of range    
STOCK-BASED COMPENSATION PLANS    
Exercise price (in dollars per share) $ 43.58