Note 2 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($)		3 Months Ended		9 Months Ended
		Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Revenues		$ 10,803,000	$ 9,052,000	$ 30,500,000	$ 27,074,000
Value Line’s non-voting revenues interest		3,033,000	1,997,000	8,389,000	6,060,000
EAM's net income (1)		4,952,000	2,451,000	12,853,000	8,857,000
EAM Trust [Member]
Other income		89,000	109,000	147,000	153,000
Investment management fee waivers and reimbursements		15,000	108,000	233,000	329,000
12b-1 fee waivers		178,000	149,000	517,000	483,000
Value Line’s non-voting revenues interest		3,033,000	1,997,000	8,389,000	6,060,000
EAM's net income (1)	[1]	844,000	426,000	1,990,000	1,610,000
EAM Trust [Member] | Investment Advice [Member]
Revenues		5,921,000	3,987,000	16,531,000	12,277,000
EAM Trust [Member] | Distribution and Shareholder Service [Member]
Revenues		$ 2,210,000	$ 1,625,000	$ 6,275,000	$ 5,056,000

[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.