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, 2022	Oct. 31, 2021	Jul. 31, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2022	Jan. 31, 2021
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ (49,257)	$ 2,030	$ 2,981	$ 18,445	$ 23,122	$ 16,059	$ (44,246)	$ 57,626
Denominator for basic net earnings per common share - weighted-average shares	16,569,881			16,994,975			16,599,369	16,974,701
Effect of dilutive securities:
Stock options and restricted stock units	0			52,000			0	62,000
Diluted (in shares)	16,569,881			17,047,211			16,599,369	17,036,586
Net earnings (loss) per share
Basic (in usd per share)	$ (2.97)			$ 1.09			$ (2.67)	$ 3.39
Diluted (in usd per share)	$ (2.97)			$ 1.08			$ (2.67)	$ 3.38
Stock excluded from the calculation of net earnings per share (shares)	40,973			0			47,878	0