Investments - Equity Method Investment (Detail Textuals 1) (USD $)	9 Months Ended
	Jan. 31, 2013	Apr. 30, 2012
Schedule of Equity Method Investments [Line Items]
Investment in EAM Trust (1)	$ 57,465,000	$ 56,331,000
Non-voting profits interest ("Profits Interest")	50.00%
EAM Trust
Schedule of Equity Method Investments [Line Items]
Investment in EAM Trust (1)	57,465,000	56,331,000
Fair value of contributed capital at inception	55,805,000	55,805,000
Cash and liquid securities in excess of working capital requirements contributed to capital account	5,820,000	5,820,000
Non-voting profits interest ("Profits Interest")	50.00%
Payable to VLI for its accrued non-voting revenues and non-voting profits interests	$ 1,588,000