Presentation and Summary of Significant Accounting Policies - Diluted Earnings per Share for Class B Common Shares Using Two-Class Method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic (in shares)		33,365	32,559	31,747
Diluted (in shares)		34,305	33,169	32,367
Basic, EPS (in usd per share)	[1]	$ 0.38	$ 0.25	$ 0.21
Diluted (in usd per share)		$ 0.37	$ 0.24	$ 0.21
Class B Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed and distributed earnings, Per basic		$ 697	$ 452	$ 387
Reallocation of undistributed earnings from Class A Common Shares to Class B Common Shares		4	5	5
Net earnings		$ 701	$ 457	$ 392
Basic (in shares)		1,822	1,822	1,822
Diluted (in shares)		1,822	1,822	1,822
Basic, EPS (in usd per share)		$ 0.38	$ 0.25	$ 0.21
Diluted (in usd per share)		$ 0.38	$ 0.25	$ 0.22

[1] Diluted per share amounts for Class A shares are shown above. Diluted per share for Class B shares under the two-class method are $0.38, $0.25 and $0.22 for the years ended April 30, 2022, 2021 and 2020, respectively. See Note 1 to the Consolidated Financial Statements.