Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenues:
Commissions	$ 561,081		$ 445,260		$ 345,520
Principal transactions	343,213		453,533		458,188
Investment banking	199,584		218,104		125,807
Asset management and service fees	228,834		193,159		117,357
Interest	89,466		65,326		46,860
Other income	19,731		19,855		9,138
Total revenues	1,441,909		1,395,237		1,102,870
Interest expense	25,347		13,211		12,234
Net revenues	1,416,562		1,382,026		1,090,636
Non-interest expenses:
Compensation and benefits	900,421		1,056,202		718,115
Occupancy and equipment rental	121,929		115,742		89,741
Communications and office supplies	75,589		69,929		54,745
Commissions and floor brokerage	27,040		26,301		23,416
Other operating expenses	152,975		114,081		84,205
Total non-interest expenses	1,277,954		1,382,255		970,222
Income before income tax expense	138,608		(229)		120,414
Provision for income taxes	$ 54,474		$ (2,136)		$ 44,616
Earnings per common share:
Basic	$ 1.61	[1]	$ 0.04	[1]	$ 1.79	[1]
Diluted	$ 1.33		$ 0.03		$ 1.56
Weighted average number of common shares outstanding:
Basic	52,418	[1]	48,723	[1]	42,445	[1]
Diluted	63,058		57,672		48,441

[1] Diluted earnings per share is computed on the basis of the weighted average number of shares of common stock plus the effect of dilutive potential common shares outstanding during the period using the treasury stock method. Diluted earnings per share include stock options and units.