Diluted Earnings Per Share for Class B Common Shares Using Two-Class Method (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Oct. 31, 2014		Oct. 31, 2013		Oct. 31, 2014		Oct. 31, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings	$ 1,175		$ 3,693		$ 2,709		$ 5,286
Basic weighted average common shares outstanding	28,270		27,448		28,252		27,406
Weighted Average Number of Shares Outstanding, Diluted	28,586		27,874		28,595		27,841
Basic, EPS	$ 0.04	[1]	$ 0.13	[1]	$ 0.10	[1]	$ 0.19	[1]
Diluted, EPS	$ 0.04	[1]	$ 0.13	[1]	$ 0.10	[1]	$ 0.19	[1]
Class B Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Class B Conversion	108		348		248		498
Reallocation of Undistributed Earnings	2		(1)		3		(4)
Net earnings	$ 110		$ 347		$ 251		$ 494
Basic weighted average common shares outstanding	2,587		2,587		2,587		2,587
Weighted Average Number of Shares Outstanding, Diluted	2,587		2,587		2,587		2,587
Basic, EPS	$ 0.04		$ 0.13		$ 0.10		$ 0.19
Diluted, EPS	$ 0.04		$ 0.13		$ 0.10		$ 0.19

[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 $0.13 for the three months ended October 31, 2014 and 2013 and $0.10 and $0.19 for the six months ended October 31, 2014 and 2013, respectively. See Note D to the Condensed Consolidated Financial Statements.