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		9 Months Ended
		Jan. 31, 2023	Jan. 31, 2022	Jan. 31, 2023	Jan. 31, 2022
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic weighted average common shares outstanding (in shares)		33,759	33,490	33,711	33,293
Diluted EPS for class B common shares (in shares)		33,965	34,578	34,006	34,325
Basic EPS (in usd per share)	[1]	$ 0.10	$ 0.09	$ 0.22	$ 0.28
Class B Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed and distributed earnings		$ 180	$ 160	$ 407	$ 502
Reallocation of undistributed earnings/losses from Class A Common Shares to Class B Common Shares		1	2	2	4
Net earnings		$ 181	$ 162	$ 409	$ 506
Basic weighted average common shares outstanding (in shares)		1,822	1,822	1,822	1,822
Diluted EPS for class B common shares (in shares)		1,822	1,822	1,822	1,822
Basic EPS (in usd per share)		$ 0.10	$ 0.09	$ 0.22	$ 0.28
Diluted EPS (in usd per share)		$ 0.10	$ 0.09	$ 0.22	$ 0.28

[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 $0.09 for the three months ended January 31, 2023 and 2022 and $0.22 and $0.28 for the nine months ended January 31, 2023 and 2022. See Note D to the Condensed Consolidated Financial Statements.