Note 2 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Revenues		$ 10,210	$ 10,080	$ 20,538	$ 19,697
Value Line’s non-voting revenues interest		3,729	2,768	7,009	5,356
Net Income (Loss) Attributable to Parent, Total		5,056	4,211	10,173	7,901
EAM Trust [Member]
Other income		5	5	115	58
Investment management fee waivers and reimbursements		76	109	119	218
12b-1 fee waivers		165	166	322	339
Value Line’s non-voting revenues interest		3,729	2,768	7,009	5,356
Net Income (Loss) Attributable to Parent, Total	[1]	970	580	1,698	1,146
EAM Trust [Member] | Investment Advice [Member]
Revenues		7,181	5,463	13,491	10,610
EAM Trust [Member] | Distribution and Shareholder Service [Member]
Revenues		$ 2,454	$ 2,086	$ 4,755	$ 4,065

[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.