Basic Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total	$ 0.37	[1]	$ 0.38	[1]	$ 0.43	[1]
Basic weighted average common shares	27,636		27,173		26,455
Class A Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings	$ 0.30		$ 0.48		$ 0.36
Undistributed earnings/(loss)	$ 0.07		$ (0.10)		$ 0.07
Total	$ 0.37	[2]	$ 0.38	[2]	$ 0.43	[2]
Distributed earnings	$ 7,584		$ 11,796		$ 8,642
Undistributed earnings/(loss)	1,786		(2,377)		1,595
Total	9,370		9,419		10,237
Basic weighted average common shares	25,049		24,586		23,840
Class B Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings	$ 0.30		$ 0.48		$ 0.36
Undistributed earnings/(loss)	$ 0.07		$ (0.10)		$ 0.07
Total	$ 0.37	[2]	$ 0.38	[2]	$ 0.43	[2]
Distributed earnings	776		1,242		931
Undistributed earnings/(loss)	185		(250)		175
Total	$ 961		$ 992		$ 1,106
Basic weighted average common shares	2,587		2,587		2,615

[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 per share for Class B shares under the two-class method are $0.37, $0.38 and $0.43 for the years ended April 30, 2014, 2013 and 2012, respectively. See Note 1 to the Consolidated Financial Statements.

[2] Amounts adjusted for rounding