Stock-Based Compensation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option to purchase common stock (in shares)			1,063,000	1,189,000
Stock-based compensation expense	$ 500,000	$ 400,000	$ 946,000	$ 841,000
Income tax excess benefit	411,742	$ 12,000	$ 500,000	$ 300,000
Stock options exercised (in shares)			650,943	343,713
Total intrinsic value of options exercised			$ 3,200,000	$ 1,900,000
Unrecognized compensation cost related to unvested stock option	$ 7,000,000		$ 7,000,000
Weighted average period for unrecognized compensation cost			2 years 10 days