Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - 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)		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
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		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
Ending balance at Jan. 31, 2021		120,350			$ 3,546		$ 182	156,902	(14,721)	(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)		678,129			678,129	[1]
Proceeds from stock options exercised	[1]	$ 7,405			$ 67			7,338
Stock-based compensation		2,910						2,910
Net earnings		9,201							9,201
Dividends declared	[1]	(11,028)							(11,028)
Ending balance (in shares) at Jan. 31, 2022			36,307,695	1,821,587	36,307,695		1,821,587
Ending balance at Jan. 31, 2022		130,879			$ 3,630		$ 182	169,740	(17,114)	(25,559)
Beginning balance (in shares) at Oct. 31, 2021					36,174,808		1,821,587
Beginning balance at Oct. 31, 2021		128,847			$ 3,617		$ 182	166,969	(16,362)	(25,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised (in shares)	[1]				132,887
Proceeds from stock options exercised	[1]	1,691			$ 13			1,678
Stock-based compensation		1,093						1,093
Net earnings		2,940							2,940
Dividends declared	[1]	(3,692)							(3,692)
Ending balance (in shares) at Jan. 31, 2022			36,307,695	1,821,587	36,307,695		1,821,587
Ending balance at Jan. 31, 2022		$ 130,879			$ 3,630		$ 182	$ 169,740	$ (17,114)	$ (25,559)

[1] Amounts adjusted for rounding