Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 393,692	$ 992,932	$ 434,063
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization of property	33,264	32,785	34,464
Amortization of deferred expenses and share-based incentive compensation	341,825	320,472	295,830
Amortization and other acquisition-related costs	35,247	5,821	6,387
Deferred tax provision (benefit)	63,660	(1,100,785)	15,628
Provision pursuant to tax receivable agreement		547,691	18,307
Loss on extinguishment of debt	3,148	60,219
Gain on acquisition of portion of business already owned	(12,668)
Gain on disposal of subsidiaries		(24,388)
(Increase) decrease in operating assets:
Deposits with banks and short-term investments	(44,278)	(207,373)	8,544
Cash deposited with clearing organizations and other segregated cash	5,767	6,909	15,656
Receivables-net	(156,129)	33,145	(76,200)
Investments	71,552	64,159	(159,107)
Other assets	(55,611)	(90,138)	(111,588)
Increase (decrease) in operating liabilities:
Deposits and other payables	(17,095)	225,008	74,801
Accrued compensation and benefits and other liabilities	(61,087)	20,839	179,232
Net cash provided by operating activities	601,287	887,296	736,017
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to property	(38,749)	(26,629)	(22,184)
Disposals of property	1,096	677	2,085
Net cash used in investing activities	(37,653)	(25,952)	(20,099)
Proceeds from:
Contributions from noncontrolling interests	93	275	1,532
Issuance of senior debt, net of expenses	296,757	396,272
Excess tax benefits from share-based incentive compensation	4,071	13,300	5,149
Other financing activities	24,484
Payments for:
Senior debt	(101,441)	(509,098)
Capital lease obligations	(1,619)	(1,826)	(2,171)
Distributions to noncontrolling interests	(2,111)	(16,296)	(13,458)
Payments under tax receivable agreement	(10,086)	(1,276)
Partial extinguishment of tax receivable agreement obligation		(42,222)
Purchase of Class A common stock	(300,217)	(172,772)	(192,657)
Class A common stock dividends	(336,138)	(290,684)	(146,241)
Settlement of vested share-based incentive compensation	(56,078)	(120,116)	(85,442)
Other financing activities	(4,667)	(2,361)	(2,081)
Net cash used in financing activities	(486,952)	(746,804)	(435,369)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(49,980)	(49,037)	(55,451)
NET INCREASE IN CASH AND CASH EQUIVALENTS	26,702	65,503	225,098
CASH AND CASH EQUIVALENTS—January 1	1,132,083	1,066,580	841,482
CASH AND CASH EQUIVALENTS—December 31	1,158,785	1,132,083	1,066,580
Cash paid during the year for:
Interest	46,262	45,359	60,414
Income taxes, net of refunds	$ 72,420	$ 60,716	$ 49,235