Employees' Defined Contribution Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 28, 2018	Apr. 29, 2017	Apr. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions, employee benefit expenses	$ 7,196	$ 4,828	$ 4,375