Goodwill and Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended		3 Months Ended		3 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Reporting Unit, MBS & Rates	Dec. 31, 2011 Reporting Unit, MBS & Rates	Jun. 30, 2012 Reporting Unit, Investment Banking	Dec. 31, 2011 Reporting Unit, Investment Banking
Goodwill and Intangible Assets
Impairment of goodwill	$ 21,096	$ 21,096	$ 14,311
Changes in the carrying amount of goodwill
Goodwill at the beginning of the period	21,096	21,096		17,364	17,364	3,732	3,732
Increase/(decrease)	(21,096)			(17,364)		(3,732)
Goodwill at the end of the period					$ 17,364		$ 3,732