Basic Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Jul. 31, 2013		Jul. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total	$ 0.06	[1]	$ 0.09	[1]
Basic weighted average common shares outstanding	27,363		27,072
Class A Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings			$ 0.09
Undistributed earnings	$ 0.06
Total	$ 0.06	[2]	$ 0.09	[2]
Distributed earnings			$ 2,209
Undistributed earnings	1,443		(18)
Total	1,443		2,191
Basic weighted average common shares outstanding	24,776		24,485
Class B Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings			$ 0.09
Undistributed earnings	$ 0.06
Total	$ 0.06		$ 0.09	[2]
Distributed earnings			233
Undistributed earnings	150		(2)
Total	$ 150		$ 231
Basic weighted average common shares outstanding	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 earnings per share for Class B shares under the two-class method are $0.06 and $0.09 for the three months ended July 31, 2013 and 2012, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding