Discontinued Operations (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Other items reclassified from continuing operations	Jun. 30, 2012 Other items reclassified from continuing operations	Jun. 30, 2013 Other items reclassified from continuing operations	Jun. 30, 2012 Other items reclassified from continuing operations	Mar. 31, 2013 ClearPoint	Jun. 30, 2013 Investment Banking	Jun. 30, 2012 Investment Banking	Jun. 30, 2013 Investment Banking	Jun. 30, 2012 Investment Banking	Jun. 30, 2013 MBS & Rates	Jun. 30, 2012 MBS & Rates	Jun. 30, 2013 MBS & Rates	Jun. 30, 2012 MBS & Rates	Jun. 30, 2013 Credit Products	Jun. 30, 2012 Credit Products	Jun. 30, 2013 Credit Products	Jun. 30, 2012 Credit Products	Jun. 30, 2013 ClearPoint	Jun. 30, 2012 ClearPoint	Jun. 30, 2013 ClearPoint	Jun. 30, 2012 ClearPoint	Jun. 30, 2013 Equities division	Jun. 30, 2012 Equities division	Jun. 30, 2013 Equities division	Jun. 30, 2012 Equities division
Discontinued Operations
Loss recognized from discontinued operations									$ 1,100,000
Total net revenues	(2,934,000)	44,727,000	28,463,000	108,823,000		1,521,000	778,000	3,454,000		1,000	8,730,000	15,034,000	13,263,000	(3,621,000)	5,282,000	(4,344,000)	25,613,000	739,000	17,872,000	12,564,000	39,589,000	(53,000)	11,316,000	4,355,000	26,861,000		6,000	76,000	43,000
Total expenses	8,006,000	68,263,000	48,485,000	131,423,000	1,792,000	24,316,000	4,613,000	27,948,000		918,000	6,535,000	12,606,000	10,489,000	2,969,000	7,028,000	10,502,000	21,872,000	1,967,000	16,587,000	14,209,000	38,992,000	283,000	13,828,000	6,436,000	32,226,000	77,000	(31,000)	119,000	(104,000)
Expenses, net of revenues					(1,792,000)	(22,795,000)	(3,835,000)	(24,494,000)		(917,000)	2,195,000	2,428,000	2,774,000	(6,590,000)	(1,746,000)	(14,846,000)	3,741,000	(1,228,000)	1,285,000	(1,645,000)	597,000	(336,000)	(2,512,000)	(2,081,000)	(5,365,000)	(77,000)	37,000	(43,000)	147,000
Subtotal	(10,940,000)	(23,536,000)	(20,022,000)	(22,600,000)
Restructuring expense	(43,627,000)		(46,086,000)
Loss from discontinued operations before income taxes	(54,567,000)	(23,536,000)	(66,108,000)	(22,600,000)
Income tax expense/(benefit)		(28,000)		1,802,000
Loss from discontinued operations, net of taxes	$ (54,567,000)	$ (23,508,000)	$ (66,108,000)	$ (24,402,000)