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, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic weighted aveage common shares outstanding (in shares)		31,955	31,010	31,611	30,887
Diluted, Class A Common Shares (in shares)		32,668	31,183	32,260	31,351
Basic EPS (in usd per share)	[1]	$ 0.10	$ 0.07	$ 0.20	$ 0.16
Diluted EPS (in usd per share)	[1]	$ 0.10	$ 0.07	$ 0.19	$ 0.16
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & distributed earnings		$ 3,098	$ 2,166	$ 5,840	$ 4,635
Undistributed & distributed earnings, class B conversion (in usd per share)		188	135	357	294
Net earnings		$ 3,286	$ 2,301	$ 6,197	$ 4,929
Basic weighted aveage common shares outstanding (in shares)		30,133	29,188	29,789	29,036
Common Stock Equivalents (in shares)		713	173	649	464
Weighted average shares including common stock equivalents, diluted (in shares)		30,846	29,361	30,438	29,500
Class B Conversion (in shares)		1,822	1,822	1,822	1,851
Diluted, Class A Common Shares (in shares)		32,668	31,183	32,260	31,351
Basic EPS (in usd per share)		$ 0.10	$ 0.07	$ 0.20	$ 0.16
Diluted EPS (in usd per share)		$ 0.10	$ 0.07	$ 0.19	$ 0.16

[1] (a)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 $0.07 for the three months ended January 31, 2020 and 2019, and $0.20 and $0.16 for the nine months ended January 31, 2020 and 2019 respectively. See Note E to the Condensed Consolidated Financial Statements.