Employees' Defined Contribution Plan - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 28, 2017	Jan. 30, 2016	Jan. 28, 2017	Jan. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company contributions, employee benefit expenses	$ 919	$ 957	$ 3,159	$ 3,252