v3.26.1
INCOME TAXES - Narrative (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]    
Net deferred tax assets $ 69.7 $ 148.7
Deferred income tax liability 3,549.9 3,456.4
Deductible temporary differences 98.9 130.4
Unrecognized 215.4  
Current tax expense (income), related to pillar two income taxes 2.5 2.6
No expiry date    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Unrecognized 174.7  
No expiry date | Capital losses    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Unrecognized $ 170.5 $ 156.2