Incentive Stock Rights - Additional Information (Detail) - shares	3 Months Ended
	Jul. 31, 2015	Jul. 31, 2010	Jun. 24, 2010
Disclosure Incentive Stock Rights Additional Information [Abstract]
Incentive stock purchase right adoption date		Jun. 24, 2010
Common stock dividends right declared			1
Incentive stock rights dividend date of record		Jul. 06, 2010
Incentive stock purchase rights expiration date	Jun. 30, 2015