Redeemable Common Stock and Stock Purchase Warrant (Details)	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Oct. 31, 2012	Oct. 31, 2012	Apr. 30, 2012 Warrant [Member]	Oct. 31, 2012 Warrant [Member]
Expected term in years	6 years	6 years	3 years 10 months 24 days	3 years 4 months 24 days
Risk-free interest rates	0.90%		0.60%	0.50%
Volatility			10.20%	83.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%