Income Taxes - Summary of Valuation Allowances Against Deferred Income Taxes (Detail) - USD ($) $ in Thousands	May 03, 2020	Apr. 28, 2019	Apr. 29, 2018	Apr. 30, 2017
Valuation Allowance [Line Items]
Valuation allowance	$ 3,148	$ 748	$ 5,204	$ 536
Capital Loss Carry Forwards and Credits [Member]
Valuation Allowance [Line Items]
Valuation allowance	2,281
State and Local Jurisdiction [Member] | Loss Carryforwards and Credits [Member]
Valuation Allowance [Line Items]
Valuation allowance	$ 867	666
Internal Revenue Service (IRS) [Member] | Income Tax Credits [Member]
Valuation Allowance [Line Items]
Valuation allowance		$ 82