Variable Interest Entity - Total assets of EAM, maximum exposure to loss due to involvement with EAM and value of assets and liabilities (Details) - USD ($) $ in Thousands		Apr. 30, 2015	Apr. 30, 2014
Variable Interest Entity [Line Items]
Investment in EAM Trust		$ 58,048	$ 57,850
EAM Trust
Variable Interest Entity [Line Items]
VIE Assets		60,159	59,965
Investment in EAM Trust	[1]	$ 58,048	$ 57,850
Liabilities
Maximum Exposure to Loss		$ 58,048	$ 57,850

[1] Reported within Long Term Assets on Consolidated Balance Sheets.