Stockholders' Equity - Stock Option Activity (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Number of Options
Outstanding beginning of the period (in shares)	6,688	5,093
Options granted (in shares)	749	2,947
Options exercises (in shares)	(160)	(227)
Options forfeited (in shares)	(503)	(484)
Options expired and canceled (in shares)	(1,226)	(641)
Outstanding end of the period (in shares)	5,548	6,688
Options vested and expected to vest (in shares)	5,548
Options vested and exercisable (in shares)	3,310
Weighted Average Exercise Price
Outstanding beginning balance	$ 7.83	$ 7.83
Options Granted	4.25	4.83
Options exercised	2.36	3.95
Options forfeited	5.78	7.42
Options expired and canceled	9.81	8.14
Outstanding ending balance	5.82	$ 7.83
Options vested and expected to vest, weighted average exercise price	5.82
Options vested and exercisable, weighted average exercise price	$ 6.46
Weighted average contractual term	6 years 5 months 3 days	6 years 5 months 6 days
Options vested and expected to vest, weighted average remaining contractual term	6 years 5 months 3 days
Options vested and exercisable, weighted average remaining contractual term	5 years 11 months 23 days
Aggregate intrinsic value	$ 2,506	$ 591
Options vested and expected to vest, aggregate intrinsic value	2,506
Options vested and exercisable, aggregate intrinsic value	$ 1,253