Condensed Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Apr. 30, 2020	13,478,733
Balance at Apr. 30, 2020	$ 135	$ 88,559	$ 460,876	$ (246,911)	$ 100	$ 302,759
Issuance of common stock (in shares)	675
Issuance of common stock		50				50
Stock options exercised (in shares)	22,000
Stock options exercised		1,166				1,166
Stock based compensation		2,320				2,320
Dividends on subsidiary preferred stock			(10)			(10)
Net income			19,564			19,564
Balance (in shares) at Jul. 31, 2020	13,501,408
Balance at Jul. 31, 2020	$ 135	92,095	480,430	(246,911)	100	325,849
Balance (in shares) at Apr. 30, 2020	13,478,733
Balance at Apr. 30, 2020	$ 135	88,559	460,876	(246,911)	100	302,759
Net income						60,642
Balance (in shares) at Jan. 31, 2021	13,575,171
Balance at Jan. 31, 2021	$ 136	98,281	521,488	(256,731)	100	363,274
Balance (in shares) at Jul. 31, 2020	13,501,408
Balance at Jul. 31, 2020	$ 135	92,095	480,430	(246,911)	100	325,849
Issuance of common stock (in shares)	958
Issuance of common stock		69				69
Stock options exercised (in shares)	28,066
Stock options exercised		1,212				1,212
Purchase of treasury shares				(6,080)	0	(6,080)
Stock based compensation		1,395				1,395
Dividends on subsidiary preferred stock			(10)			(10)
Net income			21,196			21,196
Balance (in shares) at Oct. 31, 2020	13,530,432
Balance at Oct. 31, 2020	$ 135	94,771	501,616	(252,991)	100	343,631
Issuance of common stock (in shares)	787
Issuance of common stock	$ 1	73	0	0	0	74
Stock options exercised (in shares)	43,952
Stock options exercised	$ 0	2,183	0	0	0	2,183
Purchase of treasury shares	0	0	0	(3,740)	0	(3,740)
Stock based compensation	0	1,254	0	0	0	1,254
Dividends on subsidiary preferred stock	0	0	(10)	0	0	(10)
Net income	$ 0	0	19,882	0	0	19,882
Balance (in shares) at Jan. 31, 2021	13,575,171
Balance at Jan. 31, 2021	$ 136	98,281	521,488	(256,731)	100	363,274
Balance (in shares) at Apr. 30, 2021	13,591,889
Balance at Apr. 30, 2021	$ 136	98,812	564,975	(257,527)	100	406,496
Issuance of common stock (in shares)	673
Issuance of common stock		81				81
Stock options exercised (in shares)	15,281
Stock options exercised		(1,007)				(1,007)
Purchase of treasury shares				(11,618)		(11,618)
Stock based compensation		2,972				2,972
Dividends on subsidiary preferred stock			(10)			(10)
Net income			24,967			24,967
Balance (in shares) at Jul. 31, 2021	13,607,843
Balance at Jul. 31, 2021	$ 136	100,858	589,932	(269,145)	100	421,881
Balance (in shares) at Apr. 30, 2021	13,591,889
Balance at Apr. 30, 2021	$ 136	98,812	564,975	(257,527)	100	406,496
Net income						66,630
Balance (in shares) at Jan. 31, 2022	13,624,782
Balance at Jan. 31, 2022	$ 136	102,759	631,575	(284,030)	100	450,540
Balance (in shares) at Jul. 31, 2021	13,607,843
Balance at Jul. 31, 2021	$ 136	100,858	589,932	(269,145)	100	421,881
Issuance of common stock (in shares)	7,186
Issuance of common stock		68				68
Stock options exercised (in shares)	8,381
Stock options exercised	$ 0	0	0	0	0	0
Purchase of treasury shares				(8,345)		(8,345)
Stock based compensation		977				977
Dividends on subsidiary preferred stock			(10)			(10)
Net income			22,893			22,893
Balance (in shares) at Oct. 31, 2021	13,623,410
Balance at Oct. 31, 2021	$ 136	101,903	612,815	(277,490)	100	437,464
Issuance of common stock (in shares)	872
Issuance of common stock	$ 0	76	0	0	0	76
Stock options exercised (in shares)	500
Stock options exercised	$ 0	23	0	0	0	23
Purchase of treasury shares	0	0	0	(6,540)	0	(6,540)
Stock based compensation	0	757	0	0	0	757
Dividends on subsidiary preferred stock	0	0	(10)	0	0	(10)
Net income	$ 0	0	18,770	0	0	18,770
Balance (in shares) at Jan. 31, 2022	13,624,782
Balance at Jan. 31, 2022	$ 136	$ 102,759	$ 631,575	$ (284,030)	$ 100	$ 450,540