Investments - Components of assets and liabilities (Details 3) - EAM Trust - USD ($) $ in Thousands		Jan. 31, 2016	Apr. 30, 2015
Schedule of Investments [Line Items]
EAM's total assets		$ 60,259	$ 60,159
EAM's total liabilities	[1]	(3,039)	(3,104)
EAM's total equity		$ 57,220	$ 57,055

[1] At January 31, 2016 and April 30, 2015, EAM's total liabilities included a payable to VLI for its accrued non-voting revenues, interest and the 90% distributable share of its non-voting profits interest of $1,901,000 and $1,951,000, respectively.