Note 7 - Related Party Transactions (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Apr. 30, 2020
Federal Income Tax Payments to Parent	$ 700,000
Ownership Percentage By Parent	89.78%
Value Line Inc [Member]
Revenue from Related Parties	$ 95,000	75,000
Accounts Receivable, Related Parties	0		$ 0
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 4,300,000,000	$ 3,400,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities	26.00%
Non Voting Profits Interest Percent	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	51.77%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	$ 3,607,000		$ 2,949,000
EAM Trust [Member] | Minimum [Member]
Non Voting Revenues Interest Percent	41.00%		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%		55.00%