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, 2016		Oct. 31, 2015	Oct. 31, 2016		Oct. 31, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic		$ 412		$ 2,153	$ 2,100		$ 4,725
Basic weighted average common shares outstanding		29,135		28,660	29,037		28,637
Diluted, Class A Common Shares		29,548		28,941	29,398		28,910
Basic, EPS	[1]	$ 0.01		$ 0.08	$ 0.07		$ 0.16
Diluted, EPS	[1]	$ 0.01		$ 0.07	$ 0.07		$ 0.16
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic		$ 378		$ 1,959	$ 1,929		$ 4,299
Undistributed & Distributed Earnings, Class B Conversion		34		194	171		426
Net Income (Loss) Available to Common Stockholders, Diluted, Total		$ 412		$ 2,153	$ 2,100		$ 4,725
Basic weighted average common shares outstanding		26,703		26,073	26,580		26,050
Common Stock Equivalents		413		281	362		273
Weighted Average Number of Shares Including Common Stock Equivalents, Diluted		27,116		26,354	26,942		26,323
Class B Conversion		2,432		2,587	2,457		2,587
Diluted, Class A Common Shares		29,548		28,941	29,399		28,910
Basic, EPS		$ 0.01	[2]	$ 0.08	$ 0.07	[2]	$ 0.16
Diluted, EPS		$ 0.01	[2]	$ 0.07	$ 0.07	[2]	$ 0.16

[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 $0.01 and $0.08 for the three months ended October 31, 2016 and 2015, and $0.07 and $0.16 for the six months ended October 31, 2016 and 2015, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding