Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (2,728)	$ (3,114)	$ (11,967)	$ (18,210)
Other comprehensive gain (loss), net of tax:
Foreign currency translation adjustment	111	(453)	(1,015)	(526)
Unrealized loss on investments	(14)	(34)	(16)	(33)
Total other comprehensive gain (loss), net of tax	97	(487)	(1,031)	(559)
Comprehensive loss	$ (2,631)	$ (3,601)	$ (12,998)	$ (18,769)