Goodwill and Intangible Assets (Details 2) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended								9 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2011 Investment Banking	Sep. 30, 2012 Customer relationships Minimum	Sep. 30, 2012 Customer relationships Maximum	Sep. 30, 2012 Customer relationships MBS & Rates	Dec. 31, 2011 Customer relationships MBS & Rates	Sep. 30, 2012 Customer relationships Credit Products	Dec. 31, 2011 Customer relationships Credit Products	Sep. 30, 2012 Customer relationships ClearPoint	Dec. 31, 2011 Customer relationships ClearPoint	Sep. 30, 2012 Trade name	Sep. 30, 2011 Trade name Investment Banking	Dec. 31, 2011 Trade name Investment Banking	Sep. 30, 2012 Trade name Investment Banking
Intangible assets (amortizable):
Gross carrying amount									$ 641,000	$ 641,000	$ 795,000	$ 795,000	$ 803,000	$ 803,000			$ 7,300,000	$ 4,066,000
Accumulated amortization									(449,000)	(410,000)	(729,000)	(610,000)	(176,000)	(100,000)			(874,000)	(1,011,000)
Impairment of intangible asset						4,600,000										3,200,000	(3,234,000)
Net carrying amount	3,940,000		3,940,000		4,311,000				192,000	231,000	66,000	185,000	627,000	703,000			3,192,000	3,055,000
Amortization period							3 years	12 years							20 years
Remaining amortization period															16 years
Total amortization expense	$ 100,000	$ 400,000	$ 400,000	$ 1,700,000