v3.26.1
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO SHAREHOLDER (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
ACCUMULATED OTHER COMPREHENSIVE LOSS ATTRIBUTABLE TO SHAREHOLDER      
Beginning of year $ 339.0 $ 155.9 $ (230.8)
Other comprehensive (loss) income 85.1 (55.0) 10.3
End of year 827.5 339.0 155.9
Accumulated other comprehensive (loss) income      
ACCUMULATED OTHER COMPREHENSIVE LOSS ATTRIBUTABLE TO SHAREHOLDER      
Beginning of year (61.4) (6.4) (16.7)
Other comprehensive (loss) income 85.1 (55.0) 10.3
End of year 23.7 (61.4) (6.4)
Cash flow hedges      
ACCUMULATED OTHER COMPREHENSIVE LOSS ATTRIBUTABLE TO SHAREHOLDER      
Beginning of year (92.5) (20.7) (26.3)
Other comprehensive (loss) income 67.5 (71.8) 5.6
End of year $ (25.0) (92.5) (20.7)
Expected reversal period 9 years    
Defined benefit plans      
ACCUMULATED OTHER COMPREHENSIVE LOSS ATTRIBUTABLE TO SHAREHOLDER      
Beginning of year $ 31.1 14.3 9.6
Other comprehensive (loss) income 17.6 16.8 4.7
End of year $ 48.7 $ 31.1 $ 14.3