Note 7 - Related Party Transactions (Details Textual) - USD ($)	9 Months Ended
	Jan. 31, 2022	Jan. 31, 2021
Revenue from Related Parties	$ 243,000	$ 272,000
Federal Income Tax Payments to Parent	$ 2,300,000	5,210,000
Ownership Percentage By Parent	90.60%
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 4,410,000,000	$ 4,900,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities	10.10%
Non Voting Profits Interest Percent	50.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	54.05%
Due from Related Parties, Total	$ 4,600,000
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%