Earnings Per Common Share - Diluted Earnings per Share for Class B Common Shares Using Two-Class Method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Jul. 31, 2020	Jul. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic weighted aveage common shares outstanding (in shares)		32,339	31,270
Diluted EPS for class B common shares (in shares)		32,932	31,951
Basic EPS (in usd per share)	[1]	$ 0.06	$ 0.04
Diluted EPS (in usd per share)	[1]	$ 0.06	$ 0.04
Class B Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & distributed earnings		$ 114	$ 70
Reallocation of undistributed earnings/losses from Class A Common Shares to Class B Common Shares		2	3
Net earnings		$ 116	$ 73
Basic weighted aveage common shares outstanding (in shares)		1,822	1,822
Diluted EPS for class B common shares (in shares)		1,822	1,822
Basic EPS (in usd per share)		$ 0.06	$ 0.04
Diluted EPS (in usd per share)		$ 0.06	$ 0.04

[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.