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			9 Months Ended
		Jan. 31, 2017		Jan. 31, 2016	Jan. 31, 2017		Jan. 31, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic		$ 2,243		$ 2,111	$ 4,343		$ 6,836
Basic weighted average common shares outstanding		29,333		28,778	29,136		28,684
Diluted, Class A Common Shares		29,630		29,107	29,447		28,973
Basic, EPS	[1]	$ 0.08		$ 0.07	$ 0.15		$ 0.24
Diluted, EPS	[1]	$ 0.08		$ 0.07	$ 0.15		$ 0.24
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic		$ 2,056		$ 1,922	$ 3,987		$ 6,221
Undistributed & Distributed Earnings, Class B Conversion		187		189	357		615
Net Income (Loss) Available to Common Stockholders, Diluted, Total		$ 2,243		$ 2,111	$ 4,343		$ 6,836
Basic weighted average common shares outstanding		26,901		26,191	26,687		26,097
Common Stock Equivalents		297		329	312		289
Weighted Average Number of Shares Including Common Stock Equivalents, Diluted		27,198		26,520	26,999		26,386
Class B Conversion		2,432		2,587	2,448		2,587
Diluted, Class A Common Shares		29,630		29,107	29,447		28,973
Basic, EPS		$ 0.08	[2]	$ 0.07	$ 0.15	[2]	$ 0.24
Diluted, EPS		$ 0.08	[2]	$ 0.07	$ 0.15	[2]	$ 0.24

[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 $0.08 and $0.07 for the three months ended January 31, 2017 and 2016, and $0.15 and $0.24 for the nine months ended January 31, 2017 and 2016, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding