Note 7 - Related Party Transactions (Details Textual) - USD ($)	6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Apr. 30, 2021
Revenue from Related Parties	$ 175,000	$ 206,000
Federal Income Tax Payments to Parent	$ 2,300,000	3,660,000
Ownership Percentage By Parent	90.44%
Value Line Inc [Member]
Accounts Receivable, Related Parties	$ 0		$ 0
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 5,000,000,000.0	$ 4,500,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities	12.50%
Non Voting Profits Interest Percent	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	53.87%
Due from Related Parties, Total	$ 4,830,000
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%