LEASES - Narrative (Details) - CAD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Disclosure of quantitative information about right-of-use assets [line items] | ||
| Depreciation | $ 73.4 | $ 65.3 |
| Short-term lease, low-value assets, and variable lease payments expenses | 17.5 | 21.0 |
| Net book value of property, plant and equipment leased under operating lease to third parties | 123.4 | 115.9 |
| Cost of sales | ||
| Disclosure of quantitative information about right-of-use assets [line items] | ||
| Depreciation | 72.7 | 64.0 |
| Selling, general and administrative expense | ||
| Disclosure of quantitative information about right-of-use assets [line items] | ||
| Depreciation | $ 0.7 | $ 1.3 |