Inventories (Detail) - USD ($) $ in Thousands	Jul. 30, 2017	Apr. 30, 2017		Jul. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 6,956	$ 6,456		$ 6,779
Work-in-process	2,782	3,095		3,224
Finished goods	45,489	41,931		38,128
Inventories	$ 55,227	$ 51,482	[1]	$ 48,131

[1] Derived from audited financial statements.