Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income (loss)	$ 135,692	$ 208,004	$ 126,524
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Bad debt expense	2,399	1,044	2,895
Depreciation and amortization	4,965	4,625	3,544
Equity-based compensation	124,212	123,037	96,295
Deferred tax provision	3,665	6,538	191,697
Gain on equity method investment	(20,714)		(41,652)
Gain/(Loss) on remeasurement of amount due pursuant to tax receivable agreement			(134,665)
Other	(7,333)	(3,878)	(1,432)
Changes in assets and liabilities:
Accounts receivable	7,057	963	(35,607)
Accrued and other receivables	3,644	(6,036)	2,220
Prepaid expenses and other assets	(2,203)	(610)	(5,388)
Deferred compensation	(2,924)	22	(61)
Compensation payable	(35,381)	53,083	11,853
Accounts payable, accrued expenses and other liabilities	(2,569)	(766)	3,313
Deferred revenue	(4,051)	2,126	1,975
Dividends received	2,848	2,737	11,672
Net cash provided by (used in) operating activities	209,307	390,889	233,183
Cash flows from investing activities
Purchase of investments	(212,415)	(183,972)	(179,807)
Proceeds from sales of investments	120,102	199,810	115,640
Proceeds from partial sale of equity method investment	46,907
Note payments received from employees		366	781
Notes issued to employees			(400)
Purchase of equipment and leasehold improvements	(6,467)	(6,920)	(5,647)
Net cash provided by (used in) investing activities	(51,873)	9,284	(69,433)
Cash flows from financing activities
Dividends and distributions	(209,178)	(313,827)	(255,694)
Payments under tax receivable agreement	(13,798)	(10,994)	(10,386)
Proceeds from exercise of stock options	21,459	6,846	6,055
Treasury stock purchases	(51,175)	(33,473)	(12,258)
Class A partnership units and other equity purchased		(293)	(229)
Net cash provided by (used in) financing activities	(252,692)	(351,741)	(272,512)
Effect of exchange rate fluctuations on cash, cash equivalents, and restricted cash	2,059	(555)	3,071
Net increase (decrease) in cash, cash equivalents, and restricted cash	(93,199)	47,877	(105,691)
Cash, cash equivalents, and restricted cash, beginning of period	261,771	213,894	319,585
Cash, cash equivalents, and restricted cash, end of period	168,572	261,771	213,894
Cash paid during the period for:
Income taxes	13,405	23,491	31,837
Dividends paid, declared in the prior year			68,066
Other non-cash activity
Dividend equivalents issued	33,299	49,601	24,657
Class A Partnership Units or other equity converted into Class A Common Stock	1,267	30,901	55,901
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	$ 2,397	$ 677	$ 36