Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss applicable to common stockholders	$ (3,114)	$ (4,123)	$ (18,210)	$ (25,596)
Other comprehensive loss, net of tax:
Foreign currency translation adjustment	(453)	(510)	(526)	(968)
Unrealized loss on investments	(34)	(57)	(33)	(39)
Total other comprehensive loss, net of tax	(487)	(567)	(559)	(1,007)
Comprehensive loss	$ (3,601)	$ (4,690)	$ (18,769)	$ (26,603)