Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 28, 2017	Jan. 30, 2016	Jan. 28, 2017	Jan. 30, 2016
Income taxes
Provision (benefit) for income taxes	$ 1,102,000	$ (1,133,000)	$ (2,809,000)	$ (2,821,000)
Effective tax benefit rate (as a percent)	(101.90%)	(22.50%)	13.50%	(361.20%)
Reversal of reserve			$ 968,000