Rehabilitation and Closure Cost Provision - Description of Changes to the Reclamation (Detail) - CAD ($) $ in Thousands	12 Months Ended
Apr. 30, 2018	Apr. 30, 2017
Description Of Closure And Rehabilitation Provisions [Abstract]
Beginning balance	$ 1,131	$ 1,091
Accretion expense	64	80
Foreign exchange fluctuation	(33)	(40)
Ending balance	$ 1,162	$ 1,131

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 2017-01-01
-Section D Examples: disclosures
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=sect_DExamples:disclosures&doctype=Illustrative%20Examples
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 87
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_87&doctype=Standard
-URIDate 2017-03-09

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