Summary of Cash and Cash Equivalents by Geographic Area (Detail) - USD ($) $ in Thousands	Apr. 29, 2018	Apr. 30, 2017	May 01, 2016	May 03, 2015
Cash and Cash Equivalents [Line Items]
cash and cash equivalents	$ 21,228	$ 20,795	$ 37,787	$ 29,725
United States [Member]
Cash and Cash Equivalents [Line Items]
cash and cash equivalents	9,452	1,147
China [Member]
Cash and Cash Equivalents [Line Items]
cash and cash equivalents	9,221	12,722
Canada [Member]
Cash and Cash Equivalents [Line Items]
cash and cash equivalents	2,349	2,906
Cayman Islands [Member]
Cash and Cash Equivalents [Line Items]
cash and cash equivalents	$ 206	$ 4,020