Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Apr. 30, 2018
Deferred tax liability	$ 11,573	$ 11,714
Deferred tax liability	11,573	11,714
Domestic Tax Authority [Member]
Deferred gain on deconsolidation of EAM	10,660	10,658
Deferred non-cash post-employment compensation	(372)	(372)
Depreciation and amortization	108	119
Unrealized loss (gain) on securities held for sale	321	208
Deferred charges	(182)	(331)
Other, asset	(72)
Other, liability		210
Deferred tax liability	10,607	10,492
Deferred tax liability	10,607	10,492
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,027	1,299
Deferred non-cash post-employment compensation	36	(45)
Depreciation and amortization	10	15
Other, liability	(107)	(47)
Deferred tax liability	966	1,222
Deferred tax liability	$ 966	$ 1,222