Earnings Per Common Share - Diluted Earnings per Share for Class A Common Shares Using If-Converted Method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic weighted average common shares outstanding (in shares)		32,628	31,955	32,485	31,611
Diluted, Class A Common Shares (in shares)		33,293	32,668	33,107	32,260
Basic EPS (in usd per share)	[1]	$ 0.07	$ 0.10	$ 0.16	$ 0.20
Diluted EPS (in usd per share)	[1]	$ 0.07	$ 0.10	$ 0.15	$ 0.19
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & distributed earnings		$ 2,182	$ 3,098	$ 4,755	$ 5,840
Undistributed & distributed earnings, class B conversion (in usd per share)		129	188	282	357
Net earnings		$ 2,311	$ 3,286	$ 5,037	$ 6,197
Basic weighted average common shares outstanding (in shares)		30,806	30,133	30,663	29,789
Common Stock Equivalents (in shares)		665	713	622	649
Weighted average shares including common stock equivalents, diluted (in shares)		31,471	30,846	31,285	30,438
Class B Conversion (in shares)		1,822	1,822	1,822	1,822
Diluted, Class A Common Shares (in shares)		33,293	32,668	33,107	32,260
Basic EPS (in usd per share)		$ 0.07	$ 0.10	$ 0.16	$ 0.20
Diluted EPS (in usd per share)		$ 0.07	$ 0.10	$ 0.15	$ 0.19

[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 $0.07 and $0.10 for the three months ended January 31, 2021 and 2020, respectively, and $0.16 and $0.20 for the nine months ended January 31, 2021 and 2020, respectively. See Note E to the Condensed Consolidated Financial Statements.