Share-Based Payments (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	13,890,205	14,866,038
Shares, Granted	9,793,332	741,250
Shares, Exercised	(33,750)	0
Shares, Canceled	0	(25,000)
Shares, Forfeited	(72,500)	(551,250)
Shares, Expired	(226,250)	(1,140,833)
Shares, Outstanding, Ending Balance	23,351,037	13,890,205	14,866,038
Shares, Vested and expected to vest	23,351,037	13,890,205
Shares, Exercisable	13,564,577	11,344,454
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 0.85	$ 0.88
Weighted Average Exercise Price, Granted	$ 1.23	$ 0.41
Weighted Average Exercise Price, Exercised	$ 0.63	$ 0
Weighted Average Exercise Price, Canceled	$ 0	$ 0.62
Weighted Average Exercise Price, Forfeited	$ 0.82	$ 0.72
Weighted Average Exercise Price, Expired	$ 0.73	$ 0.95
Weighted Average Exercise Price, Outstanding, Ending Balance	$ 1.01	$ 0.85	$ 0.88
Weighted Average Exercise Price, Exercisable	$ 0.85	$ 0.86
Weighted Average Remaining Contractual Term, Outstanding (in years)	7 years 6 months	7 years	7 years 7 months 6 days
Weighted Average Remaining Contractual Life (Years), Vested and expected to vest	7 years 6 months	7 years
Weighted Average Remaining Contractual Life (Years), Exercisable	6 years 1 month 6 days	6 years 10 months 24 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 89,000	$ 0
Aggregate Intrinsic Value, Outstanding, Ending Balance	985,000	89,000	0
Aggregate Intrinsic Value, Vested and expected to vest	985,000	89,000
Aggregate Intrinsic Value, Exercisable	$ 927,000	$ 54,000
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	765,000	1,410,000
Shares, Granted	0	130,000
Shares, Exercised	0	0
Shares, Canceled	0	0
Shares, Forfeited	0	0
Shares, Expired	0	(775,000)
Shares, Outstanding, Ending Balance	765,000	765,000
Shares, Vested and expected to vest	765,000	765,000
Shares, Exercisable	522,292	458,334
Directors and Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	13,125,205	13,456,038
Shares, Granted	9,793,332	611,250
Shares, Exercised	(33,750)	0
Shares, Canceled	0	(25,000)
Shares, Forfeited	(72,500)	(551,250)
Shares, Expired	(226,250)	(365,833)
Shares, Outstanding, Ending Balance	22,586,037	13,125,205
Shares, Vested and expected to vest	22,586,037	13,125,205
Shares, Exercisable	13,042,285	10,886,120