Organization and Summary of Significant Accounting Policies (Detail Textuals) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2013	Apr. 30, 2012
Schedule of Equity Method Investments [Line Items]
Non-voting profits interest ("Profits Interest")	50.00%
Short term investments (in dollars)	$ 7,751	$ 10,848
EAM Trust
Schedule of Equity Method Investments [Line Items]
Percent each voting profits interest of EAM managed by trustees	20.00%
Non-voting profits interest ("Profits Interest")	50.00%
Percentage of non voting profits interests due each quarter from EAM	90.00%
EAM Trust | Minimum
Schedule of Equity Method Investments [Line Items]
Non-voting revenues interest ("Revenues Interest")	41.00%
EAM Trust | Maximum
Schedule of Equity Method Investments [Line Items]
Non-voting revenues interest ("Revenues Interest")	55.00%