Goodwill and Intangible Assets (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Intangible assets (amortizable):
Net carrying amount	$ 5,303,000	$ 4,311,000
Total amortization expense	500,000	1,800,000	3,000,000
Investment Banking segment
Intangible assets (amortizable):
Impairment of intangible asset		(4,600,000)
Customer relationships | Minimum
Intangible assets (amortizable):
Amortization period	3 years
Customer relationships | Maximum
Intangible assets (amortizable):
Amortization period	12 years
Customer relationships | Equities segment
Intangible assets (amortizable):
Gross carrying amount	1,614,000	6,960,000
Accumulated amortization	(1,614,000)	(1,614,000)
Impairment of intangible asset		(5,346,000)
Customer relationships | MBS & Rates segment (RangeMark)
Intangible assets (amortizable):
Gross carrying amount	641,000	641,000
Accumulated amortization	(463,000)	(410,000)
Net carrying amount	178,000	231,000
Customer relationships | Credit Products segment
Intangible assets (amortizable):
Gross carrying amount	795,000	795,000
Accumulated amortization	(768,000)	(610,000)
Net carrying amount	27,000	185,000
Customer relationships | Investment Banking segment
Intangible assets (amortizable):
Gross carrying amount	5,338,000	6,500,000
Accumulated amortization	(5,338,000)	(5,338,000)
Impairment of intangible asset		(1,162,000)
Customer relationships | ClearPoint segment
Intangible assets (amortizable):
Gross carrying amount	803,000	803,000
Accumulated amortization	(201,000)	(100,000)
Net carrying amount	602,000	703,000
Intellectual property | MBS & Rates segment (RangeMark)
Intangible assets (amortizable):
Gross carrying amount	1,050,000
Accumulated amortization	(35,000)
Net carrying amount	1,015,000
Trade name | Minimum
Intangible assets (amortizable):
Amortization period	10 years
Trade name | Maximum
Intangible assets (amortizable):
Amortization period	20 years
Trade name | MBS & Rates segment (RangeMark)
Intangible assets (amortizable):
Gross carrying amount	480,000
Accumulated amortization	(8,000)
Net carrying amount	472,000
Trade name | Investment Banking segment
Intangible assets (amortizable):
Gross carrying amount	4,066,000	7,300,000
Accumulated amortization	(1,057,000)	(874,000)
Impairment of intangible asset		(3,234,000)
Net carrying amount	3,009,000	3,192,000
Covenant not to compete | Equities segment
Intangible assets (amortizable):
Gross carrying amount	293,000	330,000
Accumulated amortization	(293,000)	(293,000)
Impairment of intangible asset		(37,000)
Covenant not to compete | Investment Banking segment
Intangible assets (amortizable):
Gross carrying amount	522,000	700,000
Accumulated amortization	(522,000)	(522,000)
Impairment of intangible asset		$ (178,000)