Incentive Stock Rights - Additional Information (Details) - shares	3 Months Ended
	Jul. 31, 2015	Jul. 31, 2010	Jun. 24, 2010
Class of Stock
Incentive stock purchase right adoption date		Jun. 24, 2010
Dividend distribution of rights declared for each outstanding share of common stock			1
Incentive Stock Rights Dividend Date Of Record		Jul. 06, 2010
Date on which rights expire	Jun. 30, 2015