Variable Interest Entity - Total assets of EAM, maximum exposure to loss due to involvement with EAM and value of the assets and liabilities (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014		Apr. 30, 2013
Variable Interest Entity [Line Items]
Investment in EAM Trust	$ 57,850		$ 57,511
EAM Trust
Variable Interest Entity [Line Items]
VIE Assets	59,965		59,349
Investment in EAM Trust	57,850	[1]	57,511	[1]
Liabilities
Maximum Exposure to Loss	$ 57,850		$ 57,511

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