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		6 Months Ended
		Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic shares used in calculation of earnings per common share (in shares)		31,609	30,926	31,440	30,825
Diluted, Class A Common Shares (in shares)		32,310	31,477	32,066	31,412
Basic EPS (in usd per share)	[1]	$ 0.06	$ 0.04	$ 0.09	$ 0.09
Diluted EPS (in usd per share)	[1]	$ 0.05	$ 0.04	$ 0.09	$ 0.08
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & distributed earnings		$ 1,658	$ 1,167	$ 2,742	$ 2,469
Undistributed & distributed earnings, class B conversion (in usd per share)		101	76	169	159
Net earnings		$ 1,759	$ 1,243	$ 2,911	$ 2,628
Basic shares used in calculation of earnings per common share (in shares)		29,787	29,104	29,618	28,959
Common Stock Equivalents (in shares)		701	552	626	587
Weighted average shares including common stock equivalents, diluted (in shares)		30,488	29,656	30,244	29,546
Class B Conversion (in shares)		1,822	1,822	1,822	1,866
Diluted, Class A Common Shares (in shares)		32,310	31,478	32,066	31,412
Basic EPS (in usd per share)		$ 0.06	$ 0.04	$ 0.09	$ 0.09
Diluted EPS (in usd per share)		$ 0.05	$ 0.04	$ 0.09	$ 0.08

[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 $0.06 and $0.04 for the three months ended October 31, 2019 and 2018, and $0.10 and $0.09 for the six months ended October 31, 2019 and 2018 respectively. See Note E to the Condensed Consolidated Financial Statements.