Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 992,932	$ 434,063	$ 165,114
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization of property	32,785	34,464	34,750
Amortization of deferred expenses, share-based incentive compensation and interest rate hedge	320,472	295,830	310,036
Amortization of intangible assets related to acquisitions	5,821	6,387	10,114
Deferred tax provision (benefit)	(1,100,785)	15,628	14,454
Provision pursuant to tax receivable agreement	547,691	18,307	1,249
Loss on extinguishment of debt	60,219		50,757
Gain on disposal of subsidiaries	(24,388)
(Increase) decrease in operating assets:
Deposits with banks and short-term investments	(207,373)	8,544	58,570
Cash deposited with clearing organizations and other segregated cash	6,909	15,656	4,811
Receivables-net	33,145	(76,200)	(30,126)
Investments	64,159	(159,107)	(61,502)
Other assets	(90,138)	(111,588)	(60,731)
Increase (decrease) in operating liabilities:
Deposits and other payables	225,008	74,801	(6,028)
Accrued compensation and benefits and other liabilities	20,839	179,232	35,229
Net cash provided by operating activities	887,296	736,017	526,697
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to property	(26,629)	(22,184)	(60,964)
Disposals of property	677	2,085	6,411
Net cash used in investing activities	(25,952)	(20,099)	(54,553)
Proceeds from:
Contributions from noncontrolling interests	275	1,532	832
Issuance of senior debt, net of expenses	396,272		493,398
Excess tax benefits from share-based incentive compensation	13,300	5,149	1,108
Payments for:
Senior debt	(509,098)		(578,464)
Capital lease obligations	(1,826)	(2,171)	(2,659)
Distributions to noncontrolling interests	(16,296)	(13,458)	(14,367)
Payments under tax receivable agreement	(1,276)
Partial extinguishment of tax receivable agreement obligation	(42,222)
Purchase of Class A common stock	(172,772)	(192,657)	(132,477)
Class A common stock dividends	(290,684)	(146,241)	(121,620)
Settlement of vested share-based incentive compensation	(120,116)	(85,442)	(132,533)
Other financing activities	(2,361)	(2,081)	(290)
Net cash used in financing activities	(746,804)	(435,369)	(487,072)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(49,037)	(55,451)	6,220
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	65,503	225,098	(8,708)
CASH AND CASH EQUIVALENTS-January 1	1,066,580	841,482	850,190
CASH AND CASH EQUIVALENTS-December 31	1,132,083	1,066,580	841,482
Cash paid during the year for:
Interest	45,359	60,414	78,671
Income taxes, net of refunds	$ 60,716	$ 49,235	$ 22,623