Goodwill and Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	3 Months Ended		3 Months Ended
	Jun. 30, 2012	Sep. 30, 2012	Jun. 30, 2012 Reporting Unit, MBS & Rates	Dec. 31, 2011 Reporting Unit, MBS & Rates	Jun. 30, 2012 Reporting Unit, Investment Banking	Sep. 30, 2011 Reporting Unit, Investment Banking item	Dec. 31, 2011 Reporting Unit, Investment Banking
Goodwill and Intangible Assets
Impairment of goodwill	$ (21,096)	$ 17,364	$ (17,364)		$ (3,732)	$ 75,700
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
Impairment	(21,096)	17,364	(17,364)		(3,732)	75,700
Goodwill at the end of the period				$ 17,364			$ 3,732
Number of investment banking employees terminated						32