Note 2 - Investments - Assets and Liabilities (Details) - USD ($) $ in Thousands		Jan. 31, 2021	Apr. 30, 2020	Jan. 31, 2020	Apr. 30, 2019
EAM's total assets		$ 115,567	$ 109,728
EAM's total liabilities (1)		51,998	56,189
EAM's total equity		63,569	53,539	$ 54,346	$ 47,524
EAM Trust [Member]
EAM's total assets		64,357	61,335
EAM's total liabilities (1)	[1]	7,186	4,192
EAM's total equity		$ 57,171	$ 57,143

[1] At January 31, 2021 and April 30, 2020, EAM's total liabilities included a payable to VLI for its accrued non-voting revenues interest and non-voting profits interest of $4,671,000 and $2,949,000, respectively.