Note 2 - Investments - Components of EAM's Investment Management Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Value Line’s non-voting revenues interest		$ 2,057	$ 1,803	$ 6,074	$ 5,389
EAM's net income (1)		8,996	1,445	13,283	9,283
EAM Trust [Member]
Investment management fees earned from the Value Line Funds, net of fee waivers		4,070	3,674	12,096	10,991
12b-1 fees and other fees, net of fee waivers		1,676	1,438	4,844	4,357
Other income		52	57	156	136
Investment management fee waivers		131	132	392	308
12b-1 fee waivers		169	235	583	700
Value Line’s non-voting revenues interest		2,057	1,803	6,074	5,389
EAM's net income (1)	[1]	$ 514	$ 262	$ 1,166	$ 786

[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.