Share-Based Payments (Details 2)	9 Months Ended
	Jan. 31, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	2,004,002
Shares, Granted	331,582
Shares, Exercised	0
Shares, Forfeited	(38,140)
Shares, Expired	(84,873)
Shares, Outstanding, Ending Balance	2,212,571
Shares, Vested and expected to vest	2,212,571
Shares, Exercisable	1,678,494
Weighted Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 5.74
Weighted Average Exercise Price, Granted | $ / shares	5.33
Weighted Average Exercise Price, Exercised | $ / shares	0
Weighted Average Exercise Price, Forfeited | $ / shares	6.64
Weighted Average Exercise Price, Expired | $ / shares	6.91
Weighted Average Exercise Price, Outstanding, Ending Balance | $ / shares	5.61
Weighted Average Exercise Price, Vested and expected to vest | $ / shares	5.61
Weighted Average Exercise Price, Exercisable | $ / shares	$ 5.76
Weighted Average Remaining Contractual Term, Outstanding, Beginning Balance (in years)	6 years 8 months 12 days
Weighted Average Remaining Contractual Life (Years), Granted	8 years 10 months 24 days
Weighted Average Remaining Contractual Term, Outstanding, Ending Balance (in years)	6 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Vested and expected to vest	6 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Exercisable	5 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance | $	$ 4,166,000
Aggregate Intrinsic Value, Granted | $	0
Aggregate Intrinsic Value, Outstanding, Ending Balance | $	1,000
Aggregate Intrinsic Value, Vested and expected to vest | $	1,000
Aggregate Intrinsic Value, Exercisable | $	$ 1,000
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	57,917
Shares, Granted	0
Shares, Exercised	0
Shares, Forfeited	0
Shares, Expired	(6,667)
Shares, Outstanding, Ending Balance	51,250
Shares, Vested and expected to vest	51,250
Shares, Exercisable	34,271
Directors and Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	1,946,085
Shares, Granted	331,582
Shares, Exercised	0
Shares, Forfeited	(38,140)
Shares, Expired	(78,206)
Shares, Outstanding, Ending Balance	2,161,321
Shares, Vested and expected to vest	2,161,321
Shares, Exercisable	1,644,223