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	Apr. 30, 2013	Apr. 30, 2012
Deferred Tax Assets and Liabilities [Line Items]
Total federal tax benefit	$ 227	$ 442
Deferred gain on deconsolidation of EAM	(50,510)
Deferred non-cash post-employment compensation	1,770
Total federal, state and local tax liabilities	21,326	20,424
Federal Tax Benefit (Liability)
Deferred Tax Assets and Liabilities [Line Items]
Net operating loss		126
Unrealized gains on securities available-for-sale	(136)	(46)
Operating lease exit obligation	13	153
Deferred professional fees	49	80
Deferred charges	265	76
Total federal tax benefit	191	389
Deferred gain on deconsolidation of EAM	17,679	17,679
Deferred non-cash post-employment compensation	(619)	(619)
Depreciation and amortization	1,642	1,032
Other	262	120
Total federal, state and local tax liabilities	18,964	18,212
State and Local Tax Liability (Benefit)
Deferred Tax Assets and Liabilities [Line Items]
Net operating loss		15
Other	36	38
Total federal tax benefit	36	53
Deferred gain on deconsolidation of EAM	2,243	2,182
Deferred non-cash post-employment compensation	(79)	(76)
Depreciation and amortization	208	127
Deferred professional fees	(10)	(21)
Total federal, state and local tax liabilities	$ 2,362	$ 2,212