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, 2020					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
Stock-based compensation		546						546
Net earnings		2,034							2,034
Dividends declared	[1]	(3,571)							(3,571)
Ending balance (in shares) at Jul. 31, 2020					35,231,396		1,821,587
Ending balance at Jul. 31, 2020		120,814			$ 3,523		$ 182	153,218	(10,550)	(25,559)
Beginning balance (in shares) at Apr. 30, 2021			35,629,566	1,821,587	35,629,566		1,821,587
Beginning balance at Apr. 30, 2021		$ 122,391			$ 3,563		$ 182	159,492	(15,287)	(25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)		399,000			399,000	[1]
Proceeds from stock options exercised	[1]	$ 4,072			$ 40			4,032
Stock-based compensation		775						775
Net earnings		2,947							2,947
Dividends declared		(3,651)							(3,651)
Ending balance (in shares) at Jul. 31, 2021			36,028,566	1,821,587	36,028,566		1,821,587
Ending balance at Jul. 31, 2021		$ 126,534			$ 3,603		$ 182	$ 164,299	$ (15,991)	$ (25,559)

[1] Amounts adjusted for rounding