Note 7 - Related Party Transactions (Details Textual) - USD ($)	3 Months Ended
Jul. 31, 2018	Jul. 31, 2017	Apr. 30, 2018
Ownership Percentage By Parent	89.11%
Value Line Inc [Member]
Revenue from Related Parties	$ 73,000	$ 70,000
Accounts Receivable, Related Parties	0		$ 0
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 2,660,000,000	$ 2,490,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities	7.00%
Non Voting Profits Interest Percent	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	50.30%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	$ 2,279,000		$ 2,113,000
EAM Trust [Member] \| Minimum [Member]
Non Voting Revenues Interest Percent	41.00%
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement	90.00%
EAM Trust [Member] \| Maximum [Member]
Non Voting Revenues Interest Percent	55.00%

For an unclassified balance sheet, amount of receivables arising from transactions with related parties.

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