Net Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 2,981	$ 16,059
Denominator for basic net earnings per common share - weighted-average shares	16,660,833	16,936,832
Effect of dilutive securities:
Stock options and restricted stock units	55,000	77,000
Diluted (in shares)	16,716,167	17,013,444
Net earnings per share
Basic (in usd per share)	$ 0.18	$ 0.95
Diluted (in usd per share)	$ 0.18	$ 0.94
Stock excluded from the calculation of net earnings per share (shares)	0	0