Acquisition of KBW, Inc. (Results of Operations on Acquisition Included Consolidated Financial Statements) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Acquisition of KBW, Inc.
Total net revenues	$ 467,213	$ 469,382
Net income	$ (61,688)	$ 35,185
Basic	$ (1.03)	$ 0.59
Diluted	$ (1.03)	$ 0.51