Earnings Per Common Share - Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total (in usd per share)	[1]	$ 0.10	$ 0.02	$ 0.19	$ 0.08
Basic weighted aveage common shares outstanding (in shares)		33,337,000	32,489,000	33,195,000	32,414,000
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	$ 0.22	$ 0.22
Undistributed losses (in usd per share)		(0.01)	(0.09)	(0.03)	(0.14)
Total (in usd per share)		$ 0.10	$ 0.02	$ 0.19	$ 0.08
Distributed earnings		$ 3,475	$ 3,375	$ 6,926	$ 6,745
Undistributed losses		(342)	(2,722)	(1,007)	(4,172)
Total		$ 3,133	$ 653	$ 5,919	$ 2,573
Basic weighted aveage common shares outstanding (in shares)		31,515,000	30,667,000	31,373,000	30,592,000
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	$ 0.22	$ 0.22
Undistributed losses (in usd per share)		(0.01)	(0.09)	(0.03)	(0.14)
Total (in usd per share)		$ 0.10	$ 0.02	$ 0.19	$ 0.08
Distributed earnings		$ 201	$ 201	$ 401	$ 402
Undistributed losses		(20)	(162)	(59)	(249)
Total		$ 181	$ 39	$ 342	$ 153
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 $0.10 and $0.02 for the three months ended October 31, 2021 and 2020 and $0.19 and $0.09 for the six months ended October 31, 2021 and 2020. See Note D to the Condensed Consolidated Financial Statements.