Note 7 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
Deferred tax liability	$ 11,714	$ 18,377
Deferred tax liability	11,714	18,377
Domestic Tax Authority [Member]
Deferred gain on deconsolidation of EAM	10,658	17,742
Deferred non-cash post-employment compensation	(372)	(619)
Depreciation and amortization	119	454
Unrealized loss (gain) on securities held for sale	208	249
Deferred charges	(331)	(415)
Other, asset	(210)
Other, liability		(200)
Deferred tax liability	10,492	17,211
Deferred tax liability	10,492	17,211
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,299	1,206
Deferred non-cash post-employment compensation	(45)	(42)
Depreciation and amortization	15	31
Other, liability	(47)	(29)
Deferred tax liability	1,222	1,166
Deferred tax liability	$ 1,222	$ 1,166