Acquisitions (Results of Operations on Acquisition Included Consolidated Financial Statements) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition [Line Items]
Total net revenues	$ 1,857,913	$ 1,680,056	$ 1,806,779
Net loss	112,531	52,468	28,535
Basic	$ 1.86	$ 0.89	$ 0.51
Diluted	$ 1.56	$ 0.73	$ 0.43
Thomas Weisel Partners Group, Incorporated [Member]
Business Acquisition [Line Items]
Total net revenues			1,472,905
Net loss			$ (66,809)
Basic			$ (1.38)
Diluted			$ (1.38)