Note 7 - Related Party Transactions (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
	Jul. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Jan. 01, 2021	Apr. 30, 2020
Accrued Non Voting Revenues and Non Voting Profits Interests Payable		$ 4,671,000
Federal Income Tax Payments to Parent		5,210,000	$ 3,325,000
Ownership Percentage By Parent				90.13%
Value Line Inc [Member]
Revenue from Related Parties		272,000	259,000
Accounts Receivable, Related Parties		0			$ 0
EAM Trust [Member]
Assets under Management, Carrying Amount		$ 4,900,000,000	$ 3,750,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities		30.70%
Non Voting Profits Interest Percent	50.00%	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity		52.48%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable		$ 4,671,000			$ 2,949,000
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%