Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Share-based Payment Arrangement [Abstract]
Option to purchase common stock (in shares)			1,340,000	1,093,000
Stock-based compensation expense	$ 700	$ 600	$ 1,901	$ 1,510
Income tax excess benefit	200	$ 100	$ 500	$ 600
Stock options exercised (in shares)			462,321	802,444
Total intrinsic value of options exercised			$ 2,800	$ 4,100
Unrecognized compensation cost related to unvested stock option	$ 8,000		$ 8,000
Weighted average period for unrecognized compensation cost			1 year 11 months 8 days