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
	Jul. 31, 2014		Jul. 31, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings	$ 1,534		$ 1,593
Basic weighted average common shares outstanding	28,233		27,363
Weighted Average Number of Shares Outstanding, Diluted	28,606		27,815
Basic, EPS	$ 0.05	[1]	$ 0.06	[1]
Diluted, EPS	$ 0.05	[1]	$ 0.06	[1]
Class B Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Class B Conversion	140		150
Reallocation of Undistributed Earnings	2		(2)
Net earnings	$ 142		$ 148
Basic weighted average common shares outstanding	2,587		2,587
Weighted Average Number of Shares Outstanding, Diluted	2,587
Basic, EPS	$ 0.05	[2]	$ 0.06	[2]
Diluted, EPS	$ 0.05	[2]	$ 0.06	[2]

[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 $0.05 and $0.06 for the three months ended July 31, 2014 and 2013, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding