Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Jul. 31, 2016	Jul. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total	[1]	$ 0.06	$ 0.09
Basic weighted average common shares outstanding		28,938	28,614
Class A Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings		$ 0.11	$ 0.10
Undistributed earnings		(0.05)	(0.01)
Total	[2]	$ 0.06	$ 0.09
Distributed earnings		$ 2,933	$ 2,604
Undistributed earnings		(1,383)	(264)
Total		$ 1,550	$ 2,340
Basic weighted average common shares outstanding		26,457	26,027
Class B Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distributed earnings		$ 0.11	$ 0.10
Undistributed earnings		(0.05)	(0.01)
Total	[2]	$ 0.06	$ 0.09
Distributed earnings		$ 268	$ 259
Undistributed earnings		(130)	(27)
Total		$ 138	$ 232
Basic weighted average common shares outstanding		2,481	2,587

[1] Basic per share amounts are the same for Class A and Class B Common Shares. Diluted per share amounts for Class A Common Shares are shown above. Diluted earnings per share for Class B Common Shares under the two-class method are $0.06 and $0.09 for the three months ended July 31, 2016 and 2015, respectively. See Note D to the Condensed Consolidated Financial Statements.

[2] Amounts adjusted for rounding