Earnings Per Common share - Diluted Earnings per Share for Class A Common Shares Using If-Converted Method (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic weighted average common shares outstanding		30,926	29,906	30,825	29,788
Diluted, Class A Common Shares		31,477	30,229	31,412	30,110
Basic, EPS	[1]	$ 0.04	$ 0.08	$ 0.09	$ 0.17
Diluted, EPS	[1]	$ 0.04	$ 0.08	$ 0.08	$ 0.17
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic		$ 1,167	$ 2,296	$ 2,469	$ 4,809
Undistributed & Distributed Earnings, Class B Conversion		76	184	159	396
Net earnings		$ 1,243	$ 2,480	$ 2,628	$ 5,205
Basic weighted average common shares outstanding		29,104	27,589	28,959	27,448
Common Stock Equivalents		552	323	587	322
Weighted Average Number of Shares Including Common Stock Equivalents, Diluted		29,656	27,912	29,546	27,770
Class B Conversion		1,822	2,317	1,866	2,340
Diluted, Class A Common Shares		31,478	30,229	31,412	30,110
Basic, EPS	[2]	$ 0.04	$ 0.08	$ 0.09	$ 0.17
Diluted, EPS	[2]	$ 0.04	$ 0.08	$ 0.08	$ 0.17

[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 $0.04 and $0.08 for the three months ended October 31, 2018 and 2017, and $0.09 and $0.17 for the six months ended October 31, 2018 and 2017, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding