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Income Taxes - Summary of Valuation Allowances Against Deferred Income Taxes (Detail) - USD ($)
$ in Thousands
Apr. 28, 2019
Apr. 29, 2018
Apr. 30, 2017
May 01, 2016
Valuation Allowance [Line Items]        
Valuation allowance $ 748 $ 5,204 $ 536 $ 590
U.S. State Tax [Member] | Loss Carryforwards and Credits [Member]        
Valuation Allowance [Line Items]        
Valuation allowance 666 578    
Internal Revenue Service (IRS) [Member] | Income Tax Credits [Member]        
Valuation Allowance [Line Items]        
Valuation allowance $ 82 4,550    
Poland [Member] | Loss Carryforwards [Member]        
Valuation Allowance [Line Items]        
Valuation allowance   $ 76