Disclosure of Compensation Related Costs, Share Based Payments - Schedule of Stock Option Activity (Details) - 3 months ended Jul. 31, 2015 - 2009 Stock Incentive Plan - Employee Stock Option - $ / shares	Total
Number of Option Shares
Outstanding at the beginning of the period (in shares)	401,800
Granted	0
Exercised	49,500
Forfeited	0
Outstanding at the end of the period (in shares)	352,300
Weighted Average Option Price
Outstanding at the beginning of the period (in dollars per share)	$ 36.55
Granted	0.00
Exercised	36.46
Forfeited	0.00
Outstanding at the end of the period (in dollars per share)	$ 36.56