Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Consolidated net income (loss)	$ 85,521	$ 111,499
Adjustments to reconcile consolidated net income (loss) to net cash provided by (used in) operating activities:
Fixed asset depreciation and intangible asset amortization	63,075	58,710
Employee loan amortization and reserves on employee loans	42,733	23,286
Equity-based compensation and allocations of net income to limited partnership units and FPUs	103,030	96,223
Deferred compensation expense	502	1,193
Losses (gains) on equity method investments	(966)	(3,051)
Realized losses (gains) on marketable securities	(289)	(3,528)
Unrealized losses (gains) on marketable securities	(24)	(2,197)
Loss (gains) on other investments	1,036	(20,396)
Amortization of discount (premium) on notes payable	3,204	2,216
Impairment of fixed assets, intangible assets and investments	5,238	1,302
Deferred tax provision (benefit)	(1,202)	181
Change in estimated acquisition earn-out payables	1,172	(4,371)
Forfeitures of Class A common stock		(139)
Other	3,643
Consolidated net income (loss), adjusted for non-cash and non-operating items	306,673	260,928
Decrease (increase) in operating assets:
Securities owned	(1,078)	(1,990)
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers	(588,483)	(2,529,636)
Accrued commissions receivable, net	92,714	15,115
Loans, forgivable loans and other receivables from employees and partners, net	(135,874)	(76,489)
Receivables from related parties	(3,664)	91
Other assets	(14,782)	(15,158)
Increase (decrease) in operating liabilities:
Repurchase agreements	2,089	909
Securities loaned	(13,902)	(2,140)
Accrued compensation	1,656	(5,583)
Payables to broker-dealers, clearing organizations, customers and related broker-dealers	571,965	2,529,655
Payables to related parties	(26,899)	45,047
Accounts payable, accrued and other liabilities	(48,880)	(87,169)
Net cash provided by (used in) operating activities	141,535	133,580
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of fixed assets	(28,586)	(36,618)
Capitalization of software development costs	(41,076)	(29,997)
Purchase of equity method investments	(1,103)	(1,103)
Proceeds from equity method investments	1,650	3,737
Payments for acquisitions, net of cash and restricted cash acquired	(7,871)	26,264
Proceeds from sale of marketable securities	14,237	24,626
Purchase of assets	(2,000)
Net cash provided by (used in) investing activities	(64,749)	(13,091)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of long-term debt and collateralized borrowings	(354,353)	(328,974)
Issuance of long-term debt and collateralized borrowings, net of deferred issuance costs	524,551	670,263
Earnings distributions to limited partnership interests and other noncontrolling interests	(63,109)	(74,484)
Redemption and repurchase of limited partnership interests	(11,899)	(22,736)
Dividends to stockholders	(56,814)	(131,039)
Repurchase of Class A common stock	(6)	(1,236)
Cancellation of RSUs in satisfaction of withholding tax requirements		(458)
Payments on acquisition earn-outs	(8,540)	(7,888)
Net cash provided by (used in) financing activities	29,830	103,448
Effect of exchange rate changes on Cash and cash equivalents and Cash segregated under regulatory requirements	(6,197)	(3,235)
Net increase (decrease) in Cash and cash equivalents and Cash segregated under regulatory requirements	100,419	220,702
Cash and cash equivalents and Cash segregated under regulatory requirements at beginning of period	636,114	416,778
Cash and cash equivalents and Cash segregated under regulatory requirements at end of period	736,533	637,480
Supplemental cash information:
Cash paid during the period for taxes	30,043	28,817
Cash paid during the period for interest	48,036	41,830
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	10,029	23,414
Issuance of Class A and contingent Class A common stock and limited partnership interests for acquisitions	1,377	3,038
ROU assets and liabilities	$ 17,628	$ 202,275