Consolidated Statements of Equity - 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, 2016	12,726,560
Balance at Apr. 30, 2016	$ 127	$ 64,771	$ 305,354	$ (141,535)	$ 100	$ 228,817
Issuance of common stock (in shares)	4,750,000
Issuance of common stock		142				$ 142
Stock options exercised (in shares)	196,103					264,500
Stock options exercised	$ 2	1,895				$ 1,897
Purchase of treasury shares				(20,489)		(20,489)
Tax benefit of stock based compensation		1,183				1,183
Stock based compensation		1,293				1,293
Dividends on subsidiary preferred stock			(40)			(40)
Net income			20,205			20,205
Balance (in shares) at Apr. 30, 2017	12,927,413
Balance at Apr. 30, 2017	$ 129	69,284	325,519	(162,024)	100	233,008
Issuance of common stock (in shares)	3,096,000
Issuance of common stock		115				$ 115
Stock options exercised (in shares)	216,634					323,000
Stock options exercised	$ 2	1,639				$ 1,641
Purchase of treasury shares				(42,301)		(42,301)
Stock based compensation		1,603				1,603
Dividends on subsidiary preferred stock			(40)			(40)
Net income			36,509			36,509
Balance (in shares) at Apr. 30, 2018	13,147,143
Balance at Apr. 30, 2018	$ 131	72,641	361,988	(204,325)	100	230,535
Issuance of common stock (in shares)	2,267,000
Issuance of common stock		147				$ 147
Stock options exercised (in shares)	226,620					275,000
Stock options exercised	$ 3	5,114				$ 5,117
Purchase of treasury shares				(26,577)		(26,577)
Stock based compensation		3,703				3,703
Dividends on subsidiary preferred stock			(40)			(40)
Net income			47,625			47,625
Balance (in shares) at Apr. 30, 2019	13,376,030
Balance at Apr. 30, 2019	$ 134	$ 81,605	$ 409,573	$ (230,902)	$ 100	$ 260,510