PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation	$ 204.8	$ 182.8
Discontinued operations
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation	0.0	1.4
Cost of sales
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation	204.0	180.9
Selling, general and administrative expenses
Disclosure of detailed information about property, plant and equipment [line items]
Depreciation	$ 0.8	$ 0.5

The amount of depreciation of property, plant and equipment. [Refer: Depreciation and amortisation expense; Property, plant and equipment]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2024-01-01
-Paragraph 73
-Subparagraph e
-Clause vii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=16&code=ifrs-tx-2024-en-r&anchor=para_73_e_vii&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2024-01-01
-Paragraph 75
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=16&code=ifrs-tx-2024-en-r&anchor=para_75_a&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_DepreciationPropertyPlantAndEquipment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration