Federal, State and Local Income Taxes - Tax effect of temporary differences in deferred tax asset and deferred tax liability (Details 1) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Apr. 30, 2013
Deferred Tax Assets and Liabilities [Line Items]
Total federal tax benefit	$ 238	$ 227
Total federal, state and local tax liabilities	22,077	21,326
Federal Tax Benefit (Liability)
Deferred Tax Assets and Liabilities [Line Items]
Unrealized gains on securities available-for-sale	(137)	(136)
Operating lease exit obligation		13
Deferred professional fees	49	49
Deferred charges	292	265
Total federal tax benefit	204	191
Deferred gain on deconsolidation of EAM	17,679	17,679
Deferred non-cash post-employment compensation	(619)	(619)
Depreciation and amortization	2,166	1,642
Other	410	262
Total federal, state and local tax liabilities	19,636	18,964
State and Local Tax Liability (Benefit)
Deferred Tax Assets and Liabilities [Line Items]
Other	34	36
Total federal tax benefit	34	36
Deferred gain on deconsolidation of EAM	2,253	2,243
Deferred non-cash post-employment compensation	(79)	(79)
Depreciation and amortization	276	208
Deferred professional fees	(9)	(10)
Total federal, state and local tax liabilities	$ 2,441	$ 2,362