Stock-based Payments - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 21, 2016	Apr. 30, 2017	Apr. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		2,212,757	2,004,002
Shares, Granted	1,568,191	2,420,681	343,749
Shares, Exercised		0	0
Shares, Canceled		(1,793,779)	0
Shares, Forfeited		(421,487)	(42,515)
Shares, Expired		(109,468)	(92,479)
Shares, Outstanding, Ending Balance		2,308,704	2,212,757
Shares, Vested and expected to vest		2,308,704	2,212,757
Shares, Vested		2,061,805	1,737,306
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding, Beginning Balance (in usd per share)		$ 5.58	$ 5.74
Grants in period, weighted average exercise price (in usd per share)	$ 2.10	1.99	5.33
Weighted Average Exercise Price, Exercised (in usd per share)		0.00	0.00
Weighted Average Exercise Price, Canceled (in usd per share)		4.92	0.00
Weighted Average Exercise Price, Forfeited (in usd per share)		2.03	6.90
Weighted Average Exercise Price, Expired (in usd per share)		7.86	6.97
Weighted Average Exercise Price, Outstanding, Ending Balance (in usd per share)		2.86	5.58
Weighted Average Exercise Price, Vested (in usd per share)		$ 2.93	$ 5.71
Weighted Average Remaining Contractual Term, Outstanding, Beginning Balance (in years)		6 years 1 month 6 days	6 years 8 months 12 days
Weighted Average Remaining Contractual Term, Outstanding, Ending Balance (in years)		6 years 1 month 6 days	6 years 1 month 6 days
Weighted Average Remaining Contractual Life (Years), Vested and expected to vest		6 years 1 month 6 days	6 years 1 month 6 days
Weighted Average Remaining Contractual Life (Years), Vested		5 years 10 months 25 days	5 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance		$ 10	$ 4,166
Aggregate Intrinsic Value, Outstanding, Ending Balance		1,282	10
Aggregate Intrinsic Value, Vested and expected to vest		1,282	10
Aggregate Intrinsic Value, Vested		$ 1,101	$ 9
Non- Employees
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		51,250	57,917
Shares, Granted		0	0
Shares, Exercised		0	0
Shares, Canceled		0	0
Shares, Forfeited		0	0
Shares, Expired		(1,250)	(6,667)
Shares, Outstanding, Ending Balance		50,000	51,250
Shares, Vested and expected to vest		50,000	51,250
Shares, Vested		33,336	34,271
Directors and Employees
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		2,161,507	1,946,085
Shares, Granted		2,420,681	343,749
Shares, Exercised		0	0
Shares, Canceled		(1,793,779)	0
Shares, Forfeited		(421,487)	(42,515)
Shares, Expired		(108,218)	(85,812)
Shares, Outstanding, Ending Balance		2,258,704	2,161,507
Shares, Vested and expected to vest		2,258,704	2,161,507
Shares, Vested		2,028,469	1,703,035