Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Class A Common Shares	Class B Common Shares	Common stock Class A Common Shares	Common stock Class B Common Shares	Additional paid-in capital	Retained deficit	Treasury stock
Beginning balance (in shares) at Apr. 30, 2019				33,979,739	1,821,587
Beginning balance at Apr. 30, 2019	$ 114,607			$ 3,398	$ 182	$ 138,315	$ (1,729)	$ (25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)	151,500			151,500
Proceeds from stock options exercised	$ 1,452			$ 15		1,437
Net earnings	1,152						1,152
Dividends declared	(3,451)						(3,451)
Stock-based compensation	443					443
Ending balance (in shares) at Jul. 31, 2019				34,131,239	1,821,587
Ending balance at Jul. 31, 2019	114,203			$ 3,413	$ 182	140,195	(4,028)	(25,559)
Beginning balance (in shares) at Apr. 30, 2020		35,000,649	1,821,587	35,000,649	1,821,587
Beginning balance at Apr. 30, 2020	$ 119,422			$ 3,500	$ 182	150,312	(9,013)	(25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)	230,747			230,747
Proceeds from stock options exercised	$ 2,383			$ 23		2,360
Net earnings	2,034						2,034
Dividends declared	(3,571)						(3,571)
Stock-based compensation	546					546
Ending balance (in shares) at Jul. 31, 2020		35,231,396	1,821,587	35,231,396	1,821,587
Ending balance at Jul. 31, 2020	$ 120,814			$ 3,523	$ 182	$ 153,218	$ (10,550)	$ (25,559)