Net Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 26,881	$ 24,767
Denominator for basic net earnings per common share - weighted-average shares	16,864,870	17,534,114
Effect of dilutive securities:
Stock options and restricted stock units	43,000	85,000
Denominator for diluted net earnings per common share - weighted-average shares and assumed conversions	16,907,463	17,618,943
Net earnings per share
Basic (in usd per share)	$ 1.59	$ 1.41
Diluted (in usd per share)	$ 1.59	$ 1.41