Summary of Foreign Currency Exchange Gains (Losses) by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
Apr. 29, 2018	Apr. 30, 2017	May 01, 2016
Foreign Currency Exchange Gain And Loss [Line Items]
Foreign currency exchange gains (losses)	$ (306)	$ (9)	$ 6
China [Member]
Foreign Currency Exchange Gain And Loss [Line Items]
Foreign currency exchange gains (losses)	(298)	111	(70)
Canada [Member]
Foreign Currency Exchange Gain And Loss [Line Items]
Foreign currency exchange gains (losses)	$ (8)	$ (120)	$ 76

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30700-110894

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30690-110894

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