Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Class A Common Shares	Class B Common Shares	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Beginning Balance at Apr. 30, 2012	$ 83,030	$ 2,880	$ 259	$ 95,386	$ 8,024	$ (23,519)
Beginning Balance (in shares) at Apr. 30, 2012		28,798,490	2,587,086
Proceeds from stock options exercised (in shares)	386,356	386,356
Proceeds from stock options exercised	$ 1,990	$ 38		1,952
Stock-based compensation	1,476			1,476
Net earnings	10,411				10,411
Dividends declared	(13,037)				(13,037)
Repurchase of common shares	(759)					(759)
Tax benefit of stock option exercises	133			133
Ending Balance at Apr. 30, 2013	$ 83,244	$ 2,918	$ 259	98,947	5,398	(24,278)
Ending Balance (in shares) at Apr. 30, 2013		29,184,846	2,587,086
Proceeds from stock options exercised (in shares)	890,341	890,341
Proceeds from stock options exercised	$ 5,476	$ 90		5,386
Stock-based compensation	1,509			1,509
Net earnings	10,331				10,331
Dividends declared	(8,361)				(8,361)
Tax benefit of stock option exercises	361			361
Ending Balance at Apr. 30, 2014	$ 92,560	$ 3,008	$ 259	106,203	7,368	(24,278)
Ending Balance (in shares) at Apr. 30, 2014		30,075,187	2,587,086
Proceeds from stock options exercised (in shares)	490,912	490,912
Proceeds from stock options exercised	$ 2,725	$ 49		2,676
Stock-based compensation	1,530			1,530
Net earnings	8,128				8,128
Dividends declared	(11,337)				(11,337)
Repurchase of common shares	(1,100)					(1,100)
Tax benefit of stock option exercises	420			420
Ending Balance at Apr. 30, 2015	$ 92,926	$ 3,057	$ 259	$ 110,829	$ 4,159	$ (25,378)
Ending Balance (in shares) at Apr. 30, 2015		30,566,099	2,587,086