Disclosure of Compensation Related Costs, Share Based Payments - Schedule of Stock Option Activity (Details) - 2009 Stock Incentive Plan - Employee Stock Option	3 Months Ended
	Jul. 31, 2019 $ / shares shares
Number of option shares
Outstanding at the beginning of the period (in shares) | shares	109,827
Granted (in shares) | shares	0
Exercised (in shares) | shares	50,931
Forfeited (in shares) | shares	0
Outstanding at the end of the period (in shares) | shares	58,896
Weighted average option exercise price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 44.39
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	44.39
Forfeited (in dollars per share) | $ / shares	0
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 44.39