Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Apr. 30, 2020
Right of Use Asset	$ 193	$ 182
Deferred tax liability	12,626	12,851
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	109	108
Unrealized gain on securities held for sale	(561)	(299)
Deferred charges	(155)	(166)
Other	(345)	(207)
Deferred tax liability	10,275	10,149
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,842	2,564
Deferred non-cash post-employment compensation	(64)	(88)
Depreciation and amortization	18	44
Unrealized gain on securities held for sale	97	72
Other	458	110
Deferred tax liability	$ 2,351	$ 2,702