Income Taxes - Effective Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
May 02, 2020	Apr. 27, 2019	Apr. 28, 2018
Income Tax Disclosure [Abstract]
Computed income tax (benefit) expense at federal statutory rates	$ (2)	$ (1,038)	$ 3,779
Change in uncertain tax positions	4	(2,600)	65
Research and development tax credit	(1,621)	(1,278)	(1,598)
Other, net	(241)	587	559
Change in valuation allowances	482	(471)	(486)
GILTI	149	391	0
Base Erosion Anti-Abuse Tax (BEAT)	301	0	0
Stock compensation	318	308	336
Meals and entertainment	305	248	333
Dividends paid to retirement plan	(111)	(158)	(238)
State taxes, net of federal benefit	(84)	25	592
Impact of Tax Act	0	0	3,819
Domestic production activities deduction	0	0	(294)
Income tax (benefit) expense	$ (500)	$ (3,986)	$ 6,867

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