Accounts Receivable - Allowance for Doubtful Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($) $ in Thousands	3 Months Ended
	Jul. 30, 2017	Jul. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ (414)	$ (1,088)
Provision for bad debts	89	227
Net write-offs, net of recoveries		11
Ending balance	$ (325)	$ (850)