Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Oct. 31, 2021	Apr. 30, 2021
Deferred tax liability	$ 13,110	$ 12,905
Domestic Tax Authority [Member]
Deferred gain on deconsolidation of EAM	10,670	10,669
Deferred non-cash post-employment compensation	(372)	(372)
Depreciation and amortization	89	108
Unrealized gain on equity securities	1,008	941
Right of Use Asset	(201)	(196)
Deferred charges	(187)	(186)
Other	(119)	(218)
Deferred tax liability	10,888	10,746
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,783	1,807
Deferred non-cash post-employment compensation	(62)	(63)
Depreciation and amortization	15	18
Unrealized gain on equity securities	168	159
Other	318	238
Deferred tax liability	$ 2,222	$ 2,159