Disclosure of Compensation Related Costs, Share Based Payments - Schedule of Stock Option Activity (Details) (2009 Stock Incentive Plan, Employee Stock Option, USD $)	9 Months Ended
	Jan. 31, 2015
2009 Stock Incentive Plan | Employee Stock Option
Number of Option Shares
Outstanding at the beginning of the period (in shares)	712,024
Granted	0
Exercised	275,509
Forfeited	0
Outstanding at the end of the period (in shares)	436,515
Weighted Average Option Price
Outstanding at the beginning of the period (in dollars per share)	$ 36.73
Granted	$ 0.00
Exercised	$ 38.24
Forfeited	$ 0.00
Outstanding at the end of the period (in dollars per share)	$ 35.77