Net Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2021	Jan. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 17,195	$ 22,256	$ 16,485	$ 12,804	$ 22,163	$ 26,881	$ 55,936	$ 61,848
Denominator for basic net earnings per common share - weighted-average shares	16,994,975			16,922,231			16,974,701	16,902,255
Effect of dilutive securities:
Stock options and restricted stock units	52,000			53,000			62,000	45,000
Diluted (in shares)	17,047,211			16,974,956			17,036,586	16,947,449
Net earnings per share
Basic (in usd per share)	$ 1.01			$ 0.76			$ 3.30	$ 3.66
Diluted (in usd per share)	$ 1.01			$ 0.75			$ 3.28	$ 3.65