Note 7 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Right of Use Asset	$ 196	$ 182
Deferred tax liability	12,905	12,851
Domestic Tax Authority [Member]
Deferred gain on deconsolidation of EAM	10,669	10,669
Deferred non-cash post-employment compensation	(372)	(372)
Depreciation and amortization	108	108
Unrealized gain on securities held for sale	(941)	(299)
Deferred charges	(186)	(166)
Other	(218)	(207)
Deferred tax liability	10,746	10,149
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,807	2,564
Deferred non-cash post-employment compensation	(63)	(88)
Depreciation and amortization	18	44
Unrealized gain on securities held for sale	159	72
Other	238	110
Deferred tax liability	$ 2,159	$ 2,702