Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2022	Apr. 30, 2021
Deferred tax liability	$ 13,047	$ 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	81	108
Unrealized gain on equity securities	960	941
Right of Use Asset	(199)	(196)
Deferred charges	(164)	(186)
Other	(262)	(218)
Deferred tax liability	10,714	10,746
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	2,213	1,807
Deferred non-cash post-employment compensation	(76)	(63)
Depreciation and amortization	16	18
Unrealized gain on equity securities	163	159
Other	17	238
Deferred tax liability	$ 2,333	$ 2,159