Note 7 - Related Party Transactions (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Ownership Percentage By Parent	88.92%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	$ 2,119,000
Percent of Revenue Interest	100.00%
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement	90.00%
Federal Income Tax Payments to Parent	$ 0	$ 268,000
Value Line Inc [Member]
Accounts Receivable, Related Parties	0		$ 0
Value Line Inc [Member]
Reimbursement Revenue	70,000	84,000
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 2,490,000,000	$ 2,320,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities	7.30%
Non Voting Profits Interest Percent	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	49.73%	49.45%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	$ 2,119,000		$ 1,919,000
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement	90.00%		90.00%
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%