Restructuring (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended	12 Months Ended															0 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013 Exit of Investment Banking and Fixed Income Businesses employee	Dec. 31, 2013 Investment Banking	Dec. 31, 2013 Investment Banking Severance compensation	Dec. 31, 2013 Investment Banking Third party vendor contracts and other costs	Dec. 31, 2013 Investment Banking Intangible asset impairment	Dec. 31, 2013 Investment Banking Stock-based compensation vesting	Dec. 31, 2013 Fixed Income businesses	Dec. 31, 2013 Fixed Income businesses Severance compensation	Dec. 31, 2013 Fixed Income businesses Third party vendor contracts and other costs	Dec. 31, 2013 Fixed Income businesses Stock-based compensation vesting	Dec. 31, 2013 Fixed Income businesses Goodwill & intangible asset impairment	Dec. 31, 2013 ClearPoint	Dec. 31, 2013 ClearPoint Severance compensation	Dec. 31, 2013 ClearPoint Third party vendor contracts and other costs	Dec. 31, 2013 ClearPoint Intangible asset impairment	Dec. 31, 2013 ClearPoint Deferred compensation and other charges	Aug. 22, 2011 Equities division employee	Sep. 30, 2011 Equities division employee	Dec. 31, 2012 Equities division	Dec. 31, 2011 Equities division	Dec. 31, 2011 Equities division Severance compensation	Dec. 31, 2012 Equities division Third party vendor contracts and other costs	Dec. 31, 2011 Equities division Third party vendor contracts and other costs	Dec. 31, 2012 Equities division Stock-based compensation vesting	Dec. 31, 2011 Equities division Stock-based compensation vesting	Dec. 31, 2013 Other	Dec. 31, 2012 Other	Dec. 31, 2011 Other	Dec. 31, 2013 Other Severance compensation	Dec. 31, 2013 Other Reserve for lease commitments	Dec. 31, 2012 Other Reserve for lease commitments	Dec. 31, 2011 Other Reserve for lease commitments	Dec. 31, 2013 Other Stock-based compensation vesting	Dec. 31, 2013 Other Impairment of fixed assets and leasehold improvements	Dec. 31, 2011 Other Impairment of fixed assets and leasehold improvements
Restructuring
Number of employees impacted				150																62	62
Restructuring charges
Cash charges	$ 38,339	$ (355)	$ 5,383		$ 1,749	$ 1,417	$ 332			$ 14,457	$ 8,323	$ 6,134			$ 1,464	$ 1,263	$ 201					$ (222)	$ 4,786	$ 2,578	$ (222)	$ 2,208			$ 20,669	$ (133)	$ 597	$ 712	$ 19,957	$ (133)	$ 597
Non-cash charges	12,491	(92)	1,711		3,186			2,932	254	4,069			3,681	388	1,035			587	448			(92)	1,395				(92)	1,395	4,201		316					195	4,006	316
Restructuring expenses - Total:	$ 50,830	$ (447)	$ 7,094