Note 4 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Revenues		$ 35,868	$ 34,574	$ 34,546
Non-voting revenues interest in EAM		8,040	7,195	7,211
EAM's net income (1)		14,738	10,367	7,291
EAM Trust [Member]
Other income/(loss)		171	205	(14)
Investment management fee waivers and reimbursements		487	436	262
12b-1 fee waivers		754	923	1,071
Non-voting revenues interest in EAM		8,040	7,195	7,211
EAM's net income (1)	[1]	1,492	1,038	880
EAM Trust [Member] | Investment Advice [Member]
Revenues		15,988	14,701	14,548
EAM Trust [Member] | Distribution and Shareholder Service [Member]
Revenues		$ 6,455	$ 5,822	$ 5,669

[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.