Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option to purchase common stock (in shares)	47,000	557,000
Stock-based compensation expense	$ 443	$ 398
Income tax excess benefit	$ 62	$ 300
Stock options exercised (in shares)	151,500	295,813
Total intrinsic value of options exercised	$ 600	$ 1,700
Unrecognized compensation cost related to unvested stock option	$ 4,500
Weighted average period for unrecognized compensation cost	1 year 9 months 15 days