Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Statement of Comprehensive Income [Abstract]
Net loss applicable to common stockholders	$ (25,339)	$ (34,421)	$ (63,166)
Other comprehensive loss, net of tax:
Foreign currency translation adjustment	(255)	(934)	386
Unrealized gain (loss) on investments	15	(32)	88
Total other comprehensive income (loss), net of tax	(240)	(966)	474
Comprehensive loss	$ (25,579)	$ (35,387)	$ (62,692)