Earnings Per Common Share - Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Jul. 31, 2021	Jul. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total (in usd per share)	[1]	$ 0.09	$ 0.06
Basic weighted aveage common shares outstanding (in shares)		33,053,000	32,339,000
Class A Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings (in usd per share)		$ 0.11	$ 0.11
Undistributed losses (in usd per share)		(0.02)	(0.05)
Total (in usd per share)		$ 0.09	$ 0.06
Distributed earnings		$ 3,457	$ 3,370
Undistributed losses		(673)	(1,450)
Total		$ 2,784	$ 1,920
Basic weighted aveage common shares outstanding (in shares)		31,231,000	30,517,000
Class B Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings (in usd per share)		$ 0.11	$ 0.11
Undistributed losses (in usd per share)		(0.02)	(0.05)
Total (in usd per share)		$ 0.09	$ 0.06
Distributed earnings		$ 202	$ 201
Undistributed losses		(39)	(87)
Total		$ 163	$ 114
Basic weighted aveage common shares outstanding (in shares)		1,822,000	1,822,000

[1] Basic per share amounts are the same for Class A and Class B shares. Diluted per share amounts for Class A shares are shown above. Diluted earnings per share for Class B shares under the two-class method are $0.09 and $0.06 for the three months ended July 31, 2021 and 2020. See Note D to the Condensed Consolidated Financial Statements.