Note 2 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Revenues		$ 9,052	$ 9,094	$ 27,074	$ 26,997
Value Line’s non-voting revenues interest		1,997	2,057	6,060	6,074
EAM's net income (1)		2,451	8,996	8,857	13,283
EAM Trust [Member]
Other income		109	52	153	156
Investment management fee waivers		108	131	329	392
12b-1 fee waivers		149	169	483	583
Value Line’s non-voting revenues interest		1,997	2,057	6,060	6,074
EAM's net income (1)	[1]	426	454	1,610	1,166
EAM Trust [Member] | Investment Advice [Member]
Revenues		3,987	4,070	12,277	12,096
EAM Trust [Member] | Distribution and Shareholder Service [Member]
Revenues		$ 1,625	$ 1,676	$ 5,056	$ 4,844

[1] Represents EAM's net income, after giving effect to Value Line's non-voting revenues interest, but before distributions to voting profits interest holders and to the Company in respect of its 50% non-voting profits interest.