Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Apr. 30, 2015		Apr. 30, 2014		Apr. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total	[1]	$ 0.29		$ 0.37		$ 0.38
Basic weighted average common shares		28,283		27,636		27,173
Class A Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings		$ 0.40		$ 0.30		$ 0.48
Undistributed earnings (loss)		(0.11)		0.07		(0.10)
Total	[2]	$ 0.29		$ 0.37		$ 0.38
Distributed earnings		$ 10,301		$ 7,584		$ 11,796
Undistributed earnings (loss)		(2,914)		1,786		(2,377)
Total		$ 7,387		$ 9,370		$ 9,419
Basic weighted average common shares		25,696		25,049		24,586
Class B Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings		$ 0.40		$ 0.30		$ 0.48
Undistributed earnings (loss)		(0.11)		0.07		(0.10)
Total		$ 0.29	[2]	$ 0.37	[2]	$ 0.38
Distributed earnings		$ 1,035		$ 776		$ 1,242
Undistributed earnings (loss)		(294)		185		(250)
Total		$ 741		$ 961		$ 992
Basic weighted average common shares		2,587		2,587		2,587

[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 $0.29, $0.37 and $0.38 for the years ended April 30, 2015, 2014 and 2013, respectively. See Note 1 to the Consolidated Financial Statements.

[2] Amounts adjusted for rounding