Earnings Per Common Share - Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2022	Jan. 31, 2021
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total (in usd per share)	[1]	$ 0.09	$ 0.07	$ 0.28	$ 0.16
Basic weighted aveage common shares outstanding (in shares)		33,490,000	32,628,000	33,293,000	32,485,000
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	$ 0.33	$ 0.33
Undistributed losses (in usd per share)		(0.02)	(0.04)	(0.05)	(0.17)
Total (in usd per share)		$ 0.09	$ 0.07	$ 0.28	$ 0.16
Distributed earnings		$ 3,488	$ 3,396	$ 10,426	$ 10,142
Undistributed losses		(708)	(1,214)	(1,727)	(5,387)
Total		$ 2,780	$ 2,182	$ 8,699	$ 4,755
Basic weighted aveage common shares outstanding (in shares)		31,668,000	30,806,000	31,471,000	30,663,000
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	$ 0.33	$ 0.33
Undistributed losses (in usd per share)		(0.02)	(0.04)	(0.05)	(0.17)
Total (in usd per share)		$ 0.09	$ 0.07	$ 0.28	$ 0.16
Distributed earnings		$ 201	$ 201	$ 602	$ 602
Undistributed losses		(41)	(72)	(100)	(320)
Total		$ 160	$ 129	$ 502	$ 282
Basic weighted aveage common shares outstanding (in shares)		1,822,000	1,822,000	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 $0.07 for the three months ended January 31, 2022 and 2021 and $0.28 and $0.16 for the nine months ended January 31, 2022 and 2021. See Note D to the Condensed Consolidated Financial Statements.