v3.26.1
INCOME TAXES - Movements In Temporary Differences (Details) - CAD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period $ 151.1 $ 196.7
Recognized in income (21.9) (44.7)
Recognized in OCI (21.4) 20.3
Recognized in equity 0.5 2.4
Business combinations   (23.7)
Foreign currency exchange differences 1.0 0.1
Deferred tax liability (asset), end of period 109.3 151.1
Non-capital loss carryforwards    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period 89.7 142.5
Recognized in income 87.0 (61.3)
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   3.3
Foreign currency exchange differences 1.6 5.2
Deferred tax liability (asset), end of period 178.3 89.7
Unclaimed research & development expenditures    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period 227.8 162.1
Recognized in income (133.9) 59.0
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   0.0
Foreign currency exchange differences (4.6) 6.7
Deferred tax liability (asset), end of period 89.3 227.8
Investment tax credits    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period (76.8) (73.8)
Recognized in income (6.2) (3.0)
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   0.0
Foreign currency exchange differences 0.0 0.0
Deferred tax liability (asset), end of period (83.0) (76.8)
Property, plant and equipment and right-of-use of assets    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period (168.0) (154.1)
Recognized in income (24.4) 9.3
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   (11.1)
Foreign currency exchange differences 4.6 (12.1)
Deferred tax liability (asset), end of period (187.8) (168.0)
Intangible assets    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period (126.8) (39.0)
Recognized in income 12.3 (59.7)
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   (26.3)
Foreign currency exchange differences 1.0 (1.8)
Deferred tax liability (asset), end of period (113.5) (126.8)
Amounts not currently deductible including interest limitation    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period 110.7 76.9
Recognized in income 23.0 22.7
Recognized in OCI 0.0 0.0
Recognized in equity 0.5 2.4
Business combinations   6.5
Foreign currency exchange differences (1.6) 2.2
Deferred tax liability (asset), end of period 132.6 110.7
Government participation    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period 93.6 86.4
Recognized in income 5.0 7.2
Recognized in OCI 0.0 0.0
Recognized in equity 0.0 0.0
Business combinations   0.0
Foreign currency exchange differences 0.0 0.0
Deferred tax liability (asset), end of period 98.6 93.6
Other    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liability (asset), beginning of period 0.9 (4.3)
Recognized in income 15.3 (18.9)
Recognized in OCI (21.4) 20.3
Recognized in equity 0.0 0.0
Business combinations   3.9
Foreign currency exchange differences 0.0 (0.1)
Deferred tax liability (asset), end of period $ (5.2) $ 0.9