Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Consolidated net income (loss)	$ 108,939	$ 147,421
Less: Consolidated net income from discontinued operations, net of tax		(42,390)
Adjustments to reconcile consolidated net income (loss) to net cash provided by (used in) operating activities:
Fixed asset depreciation and intangible asset amortization	38,534	33,949
Employee loan amortization and reserves on employee loans	14,024	5,528
Equity-based compensation and allocations of net income to limited partnership units and FPUs	55,893	84,991
Deferred compensation expense	641	2,292
Losses (gains) on equity method investments	(1,521)	(3,635)
Amortization of discount (premium) on notes payable	1,368	(1,797)
Unrealized (gain) loss on marketable securities	(1,768)	(4,275)
Impairment of fixed assets, intangible assets and investments	948	1,835
Deferred tax provision (benefit)	369	2,748
Realized losses (gains) on marketable securities	(3,528)	(9,552)
Change in estimated acquisition earn-out payables	(3,422)	(881)
Losses (gains) on other investments	(20,395)	(20,565)
Forfeitures of Class A common stock		(910)
Other	734	(851)
Consolidated net income (loss), adjusted for non-cash and non-operating items	190,816	193,908
Decrease (increase) in operating assets:
Securities owned	(3,677)	(24,407)
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers	(1,333,792)	(945,086)
Accrued commissions receivable, net	(52,842)	(84,797)
Loans, forgivable loans and other receivables from employees and partners, net	(59,268)	(41,636)
Receivables from related parties	2,980	(218,096)
Other assets	(15,050)	(21,215)
Increase (decrease) in operating liabilities:
Repurchase Agreements	114	3,108
Securities loaned	(2,850)	(76,343)
Accrued compensation	(9,054)	(2,289)
Payables to broker-dealers, clearing organizations, customers and related broker-dealers	1,337,521	898,031
Payables to related parties	20,271	4,992
Accounts payable, accrued and other liabilities	(16,883)	(2,810)
Net cash provided by (used in) operating activities	58,286	(316,640)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of fixed assets	(24,839)	(13,817)
Capitalization of software development costs	(18,418)	(18,940)
Purchase of equity method investments	(735)	(368)
Proceeds from equity method investments	1,153	2,706
Investment in memberships		(642)
Payments for acquisitions, net of cash and restricted cash acquired	26,265	(1,366)
Proceeds from sale of marketable securities	24,626	95,406
Net cash provided by (used in) investing activities	8,052	62,979
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of long-term debt and collateralized borrowings	(25,594)	(7,234)
Issuance of long-term debt and collateralized borrowings, net of deferred issuance costs	324,454	70,000
Earnings distributions to limited partnership interests and other noncontrolling interests	(54,128)	(71,661)
Redemption and repurchase of limited partnership interests	(13,605)	(6,847)
Dividends to stockholders	(89,003)	(105,003)
Repurchase of Class A common stock	(1,236)	(9,711)
Cancellation of restricted stock units in satisfaction of withholding tax requirements	(458)	(647)
Proceeds from issuance of Class A common stock, net of costs		324,177
Loan from related parties, net of repayments		130,000
Payments on acquisition earn-outs	(7,534)	(7,924)
Net cash provided by (used in) financing activities	132,896	315,150
Net cash provided by (used in) operating activities from discontinued operations	0	122,484
Net cash provided by (used in) investing activities from discontinued operations	0	17,388
Net cash provided by (used in) financing activities from discontinued operations	0	(543,376)
Effect of exchange rate changes on Cash and cash equivalents, Restricted cash and Cash segregated under regulatory requirements	107	(8,015)
Net (decrease) increase in Cash and cash equivalents, Restricted cash and Cash segregated under regulatory requirements	199,341	(350,030)
Cash and cash equivalents, Restricted cash and Cash segregated under regulatory requirements at beginning of period	416,778	796,790
Cash and cash equivalents, Restricted cash and Cash segregated under regulatory requirements at end of period	616,119	446,760
Supplemental cash information:
Cash paid during the period for taxes	13,109	24,152
Cash paid during the period for interest	25,760	19,791
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	18,087	99,901
Issuance of Class A and contingent Class A common stock and limited partnership interests for acquisitions	$ 2,102	$ 7,134