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)		802,444			802,444
Proceeds from stock options exercised		$ 7,837			$ 80		7,757
Stock-based compensation		1,510					1,510
Net earnings		6,197						6,197
Dividends declared	[1]	(10,479)						(10,479)
Ending balance (in shares) at Jan. 31, 2020					34,782,183	1,821,587
Ending balance at Jan. 31, 2020		119,672			$ 3,478	$ 182	147,582	(6,011)	(25,559)
Beginning balance (in shares) at Oct. 31, 2019					34,630,682	1,821,587
Beginning balance at Oct. 31, 2019		117,866			$ 3,463	$ 182	145,554	(5,774)	(25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)					151,501
Proceeds from stock options exercised		1,480			$ 15		1,465
Stock-based compensation		563					563
Net earnings		3,286						3,286
Dividends declared	[1]	(3,523)						(3,523)
Ending balance (in shares) at Jan. 31, 2020					34,782,183	1,821,587
Ending balance at Jan. 31, 2020		119,672			$ 3,478	$ 182	147,582	(6,011)	(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)		462,321			462,321
Proceeds from stock options exercised		$ 4,735			$ 46		4,689
Stock-based compensation		1,901					1,901
Net earnings		5,037						5,037
Dividends declared	[1]	(10,745)						(10,745)
Ending balance (in shares) at Jan. 31, 2021			35,462,970	1,821,587	35,462,970	1,821,587
Ending balance at Jan. 31, 2021		120,350			$ 3,546	$ 182	156,902	(14,721)	(25,559)
Beginning balance (in shares) at Oct. 31, 2020					35,277,846	1,821,587
Beginning balance at Oct. 31, 2020		119,053			$ 3,528	$ 182	154,335	(13,433)	(25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)					185,124
Proceeds from stock options exercised		1,882			$ 18		1,864
Stock-based compensation		703					703
Net earnings	[1]	2,311						2,311
Dividends declared	[1]	(3,599)						(3,599)
Ending balance (in shares) at Jan. 31, 2021			35,462,970	1,821,587	35,462,970	1,821,587
Ending balance at Jan. 31, 2021		$ 120,350			$ 3,546	$ 182	$ 156,902	$ (14,721)	$ (25,559)

[1] Amounts adjusted for rounding