Rehabilitation and Closure Cost Provision - Description of Changes to the Reclamation (Detail) - CAD ($) $ in Thousands	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Description Of Closure And Rehabilitation Provisions [Abstract]
Beginning balance	$ 1,254	$ 1,162
Accretion expense	72	90
Foreign exchange fluctuation	(312)	2
Ending balance	$ 1,014	$ 1,254

The amount of provision for costs related to decommissioning, restoration and rehabilitation. [Refer: Other provisions]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 37
-IssueDate 2019-01-01
-Section D Examples: disclosures
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2019-en-r&doctype=Illustrative%20Examples&dita_xref=IAS37_IE_D_TI
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 37
-IssueDate 2019-01-01
-Paragraph 87
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2019-en-r&anchor=para_87&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_ProvisionForDecommissioningRestorationAndRehabilitationCosts
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant