Note 8 - Federal, State and Local Income Taxes - Schedule of Components of Deferred Tax Asset and Deferred Tax Liability (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
Total federal tax liability	$ 18,583	$ 18,377
Deferred tax liability, long term	18,583	18,377
Domestic Tax Authority [Member]
Deferred non-cash post-employment compensation	(619)	(619)
Depreciation and amortization	391	454
Other	(114)	(366)
Other	(114)	(366)
Total federal tax liability	17,405	17,211
Deferred gain on deconsolidation of EAM	17,747	17,742
Deferred tax liability, long term	17,405	17,211
State and Local Jurisdiction [Member]
Deferred non-cash post-employment compensation	(39)	(42)
Depreciation and amortization	25	31
Other	78	(29)
Other	78	(29)
Total federal tax liability	1,178	1,166
Deferred gain on deconsolidation of EAM	1,114	1,206
Deferred tax liability, long term	$ 1,178	$ 1,166