Income Taxes - Summary of Valuation Allowances Against Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Apr. 29, 2018	Apr. 30, 2017	May 01, 2016	May 03, 2015
Valuation Allowance [Line Items]
valuation allowance	$ 5,204	$ 536	$ 590	$ 922
U.S. State Tax [Member] | Loss Carryforwards and Credits [Member]
Valuation Allowance [Line Items]
valuation allowance	578	464
U.S. [Member] | Income Tax Credits [Member]
Valuation Allowance [Line Items]
valuation allowance	4,550
Poland [Member] | Loss Carryforwards [Member]
Valuation Allowance [Line Items]
valuation allowance	$ 76	$ 72