Net Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 16,485	$ 26,881
Denominator for basic net earnings per common share - weighted-average shares	16,936,832	16,864,870
Effect of dilutive securities:
Stock options and restricted stock units	77,000	43,000
Denominator for diluted net earnings per common share - weighted-average shares and assumed conversions	17,013,444	16,907,463
Net earnings per share
Basic (in usd per share)	$ 0.97	$ 1.59
Diluted (in usd per share)	$ 0.97	$ 1.59