Supplementary Cash Flow Information (Detail Textuals) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended	1 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011	Jul. 31, 2010 Prepaid and refundable income taxes	Dec. 23, 2010 Investment In EAM Trust
Supplementary Cash Flow Information [Line Items]
Federal income tax refunds			$ 1,598	$ 1,598
Investment in EAM Trust	57,511	56,331			55,805
Amount of cash paid in equity method investments			5,484		5,484
Amount of investment through FDIC insured corporate notes					1,516
Share-based compensation			$ 1,770		$ 1,770