Note 7 - Related Party Transactions - Non-voting Revenues Interest and Non-voting Profits Interests (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Value Line’s non-voting revenues interest	$ 4,104	$ 3,033	$ 11,113	$ 8,389
Non-voting profits interest in EAM	630	422	1,479	995
Revenues and Profits Distribution from Unconsolidated Entity	$ 4,734	$ 3,455	$ 12,592	$ 9,384