Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income (loss)	$ 208,004	$ 126,524	$ 141,865
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Bad debt expense	1,044	2,895	(277)
Depreciation and amortization	4,625	3,544	3,183
(Income) loss from equity method investments	(7,162)	(8,341)	(5,076)
Equity-based compensation	123,037	96,295	77,050
Deferred tax provision	6,538	191,697	(1,014)
Gain on equity method investment		(41,652)
Gain/(Loss) on remeasurement of amount due pursuant to tax receivable agreement		(134,665)
Other	3,284	6,909	2,204
Changes in assets and liabilities:
Accounts receivable	963	(35,607)	5,536
Accrued and other receivables	(6,036)	2,220	3,562
Prepaid expenses and other assets	(610)	(5,388)	1,872
Deferred compensation	22	(61)	167
Compensation payable	53,083	11,853	10,739
Accounts payable and accrued expenses	1,691	3,611	(6,219)
Deferred revenue	2,126	1,975	(4,018)
Dividends received	2,737	11,672	1,416
Other liabilities	(2,457)	(298)	584
Net cash provided by (used in) operating activities	390,889	233,183	231,574
Cash flows from investing activities
Purchase of investments	(183,972)	(179,807)	(120,906)
Proceeds from sales of investments	199,810	115,640	126,000
Return of capital from equity method investments			11
Note payments received from employees	366	781
Notes issued to employees		(400)	(852)
Purchase of equipment and leasehold improvements	(6,920)	(5,647)	(2,870)
Net cash provided by (used in) investing activities	9,284	(69,433)	1,383
Cash flows from financing activities
Dividends and distributions	(313,827)	(255,694)	(154,703)
Payments under tax receivable agreement	(10,994)	(10,386)
Proceeds from exercise of stock options	6,846	6,055
Treasury Stock Purchases	(33,473)	(12,258)	(3,314)
Class A partnership units and other equity purchased	(293)	(229)
Net cash provided by (used in) financing activities	(351,741)	(272,512)	(158,017)
Effect of exchange rate fluctuations on cash, cash equivalents, and restricted cash	(555)	3,071	(4,196)
Net increase (decrease) in cash, cash equivalents, and restricted cash	47,877	(105,691)	70,744
Cash, cash equivalents, and restricted cash, beginning of period	213,894	319,585	248,841
Cash, cash equivalents, and restricted cash, end of period	261,771	213,894	319,585
Cash paid during the period for:
Income taxes	23,491	31,837	28,613
Dividends paid, declared in the prior year		68,066
Other non-cash activity
Dividend equivalents issued	49,601	24,657	23,367
Dividend declared not paid			68,066
Class A Partnership Units or other equity converted into Class A Common Stock	30,901	55,901	835
Cumulative Effect Adjustment upon Adoption of ASU 2014-09	3,155
Cumulative Effect Adjustment upon Adoption of ASU 2016-09		658
Forfeiture of fully-vested Group LP units or other equity units	$ 677	$ 36	$ 83