Note 8 - Federal, State and Local Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Apr. 30, 2017
Deferred tax liability	$ 11,972	$ 18,377
Deferred tax liability	11,972	18,377
Domestic Tax Authority [Member]
Deferred gain on deconsolidation of EAM	10,655	17,742
Deferred non-cash post-employment compensation	(372)	(619)
Depreciation and amortization	179	454
Unrealized loss (gain) on securities held for sale	322	(366)
Other	(42)
Deferred tax liability	10,742	17,211
Deferred tax liability	10,742	17,211
State and Local Jurisdiction [Member]
Deferred gain on deconsolidation of EAM	1,298	1,206
Deferred non-cash post-employment compensation	(45)	(42)
Depreciation and amortization	22	31
Other	(45)	(29)
Deferred tax liability	1,230	1,166
Deferred tax liability	$ 1,230	$ 1,166