Note 7 - Related Party Transactions - Non-voting Revenues Interest and Non-voting Profits Interests (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Value Line’s non-voting revenues interest	$ 4,263	$ 3,729	$ 8,412	$ 7,009
Non-voting profits interest in EAM	629	485	1,285	849
Revenues and Profits Distribution from Unconsolidated Entity	$ 4,892	$ 4,214	$ 9,697	$ 7,858