Earnings Per Common Share - Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Jul. 31, 2020	Jul. 31, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total (in usd per share)	[1]	$ 0.06	$ 0.04
Basic weighted aveage common shares outstanding (in shares)		32,339	31,270
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)		(0.05)	(0.07)
Total (in usd per share)		$ 0.06	$ 0.04
Distributed earnings		$ 3,370	$ 3,245
Undistributed losses		(1,450)	(2,163)
Total		$ 1,920	$ 1,082
Basic weighted aveage common shares outstanding (in shares)		30,517	29,448
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)		(0.05)	(0.07)
Total (in usd per share)		$ 0.06	$ 0.04
Distributed earnings		$ 201	$ 206
Undistributed losses		(87)	(136)
Total		$ 114	$ 70
Basic weighted aveage common shares outstanding (in shares)		1,822	1,822

[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 $0.06 and $0.04 for the three months ended July 31, 2020 and 2019. See Note E to the Condensed Consolidated Financial Statements.