Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues:
Commissions		$ 183,771	$ 164,371	$ 364,073	$ 336,614
Principal transactions		85,542	110,717	186,275	221,399
Investment banking		161,007	144,815	285,568	280,077
Asset management and service fees		119,936	94,231	233,805	183,401
Interest		43,852	46,114	86,588	88,950
Other income		13,741	8,745	25,541	13,983
Total revenues		607,849	568,993	1,181,850	1,124,424
Interest expense		10,098	8,888	23,117	17,562
Net revenues	[1]	597,751	560,105	1,158,733	1,106,862
Non-interest expenses:
Compensation and benefits		409,998	355,268	765,691	702,257
Occupancy and equipment rental		48,346	43,237	92,516	84,019
Communications and office supplies		31,114	25,858	60,348	50,696
Commissions and floor brokerage		9,124	9,248	19,193	18,277
Other operating expenses		61,098	52,075	112,848	99,764
Total non-interest expenses		559,680	485,686	1,050,596	955,013
Income before income tax expense		38,071	74,419	108,137	151,849
Provision for income taxes		17,183	30,819	44,152	60,866
Net income		$ 20,888	$ 43,600	$ 63,985	$ 90,983
Earnings per common share
Basic		$ 0.31	$ 0.66	$ 0.94	$ 1.38
Diluted		$ 0.27	$ 0.58	$ 0.82	$ 1.20
Weighted-average number of common shares outstanding:
Basic		68,370	66,302	68,189	66,167
Diluted		77,856	75,641	77,624	75,665

[1] No individual client accounted for more than 10 percent of total net revenues for the three and six months ended June 30, 2015 or 2014.