Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Apr. 30, 2020
Right of Use Asset	$ 190	$ 182
Deferred tax liability	12,604	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	109	108
Unrealized gain on securities held for sale	(292)	(299)
Deferred charges	(165)	(166)
Other	(465)	(207)
Deferred tax liability	9,878	10,149
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	2,549	2,564
Deferred non-cash post-employment compensation	(89)	(88)
Depreciation and amortization	26	44
Unrealized gain on securities held for sale	70	72
Other	170	110
Deferred tax liability	$ 2,726	$ 2,702