Investments - Components of assets and liabilities (Details 3) (EAM Trust, USD $) In Thousands, unless otherwise specified	Jul. 31, 2013		Apr. 30, 2013
EAM Trust
Schedule of Investments [Line Items]
EAM's total assets	$ 59,261		$ 59,349
EAM's total liabilities	(2,660)	[1]	(2,814)	[1]
EAM's total equity	$ 56,601		$ 56,535

[1] At July 31, 2013 and April 30, 2013, EAM's total liabilities included a payable to VLI for its accrued non-voting revenues and non-voting profits interests of $1,752,000 and $1,621,000, respectively.