Note 4 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Revenues		$ 36,257	$ 35,868	$ 34,574
Non-voting revenues interest in EAM		8,260	8,040	7,195
EAM's net income (1)		11,150	14,738	10,367
EAM Trust [Member]
Other income		273	171	205
Investment management fee waivers and reimbursements		421	487	474
12b-1 fee waivers		654	754	923
Non-voting revenues interest in EAM		8,260	8,040	7,195
EAM's net income (1)	[1]	2,098	1,492	1,038
EAM Trust [Member] | Investment Advice [Member]
Revenues		16,715	15,988	14,701
EAM Trust [Member] | Distribution and Shareholder Service [Member]
Revenues		$ 6,811	$ 6,455	$ 5,822

[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.