Note 2 - Investments (Details Textual) - USD ($)		3 Months Ended
		Jul. 31, 2016	Jul. 31, 2015	Apr. 30, 2016
EAM Trust [Member]
Fair Value of Contributed Capital at Inception		$ 55,805,000		$ 55,805,000
Cash and Liquid Securities in Excess of Working Capital Requirements Contributed to CapitalAccount		5,820,000		5,820,000
Equity Method Investments	[1]	$ 58,123,000		57,942,000
Percentage of Non Voting Profit Interest		50.00%
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement		90.00%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable		$ 1,903,000		1,750,000
Equity Securities [Member]
Deferred Taxes on Unrealized Gains on Securities		84,000	$ 50,000
Proceeds from Sale of Available-for-sale Securities, Equity		0	0
Available-for-sale Securities, Amortized Cost Basis		3,445,000		3,445,000
Available-for-sale Securities		3,875,000		3,637,000
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent		238,000	$ (142,000)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax		430,000		192,000
AOCI Tax, Attributable to Parent		151,000		67,000
Equity Method Investments		$ 58,123,000		$ 57,942,000
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement		90.00%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable		$ 1,903,000

[1] Reported within Long Term Assets on Consolidated Balance Sheets.