Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Consolidated net income (loss)	$ 51,045	$ 33,206
Adjustments to reconcile consolidated net income (loss) to net cash provided by operating activities:
Fixed asset depreciation and intangible asset amortization	40,707	39,029
Employee loan amortization and reserves on employee loans	15,885	21,089
Equity-based compensation and allocations of net income to limited partnership units and FPUs	128,560	83,374
Deferred compensation expense	6,208	9,780
Losses (gains) on equity method investments	(1,839)	(1,751)
Amortization of discount (premium) on notes payable	(1,265)	(1,014)
Unrealized (gain) loss on marketable securities	(10,243)	2,937
Impairment of fixed assets, intangible assets and equity method investments	1,638	3,169
Deferred tax provision (benefit)	2,975	(7,671)
Sublease provision adjustment		(549)
Realized losses (gains) on marketable securities	(1,222)	(9,606)
Change in estimated acquisition earn-out payables	(3,770)	(748)
Forfeitures of Class A common stock	(224)	(99)
Other	(557)	(391)
Consolidated net income (loss), adjusted for non-cash and non-operating items	227,898	170,755
Decrease (increase) in operating assets:
Cash segregated under regulatory requirements	(29,939)	(13,288)
Reverse repurchase agreements	54,659
Securities owned	1,614	(286,219)
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers	(1,148,076)	(1,207,984)
Accrued commissions receivable, net	(78,145)	(25,454)
Loans, forgivable loans and other receivables from employees and partners, net	(46,395)	(111,519)
Receivables from related parties	(4,099)	1,203
Other assets	(8,159)	(15,942)
Increase (decrease) in operating liabilities:
Securities loaned	95,327	(117,967)
Accrued compensation	(32,575)	(12,657)
Payables to broker-dealers, clearing organizations, customers and related broker-dealers	1,109,096	1,141,883
Payables to related parties	10,373	4,075
Accounts payable, accrued and other liabilities	81,444	(9,995)
Net cash provided by (used in) operating activities	233,023	(483,109)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of fixed assets	(21,346)	(22,727)
Capitalization of software development costs	(14,341)	(10,267)
Purchase of cost and equity method investments	(888)	(1,112)
Proceeds from equity method investments	243
Payments for acquisitions, net of cash acquired	(63,295)	(113,151)
Purchase of marketable securities	0	(63,341)
Proceeds from sale of marketable securities	7,829	566,319
Capitalization of trademarks, patent defense and registration costs	(249)	(363)
Net cash provided by (used in) investing activities	(92,047)	355,358
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of collateralized borrowings	(3,523)	(3,400)
Issuance of senior notes, net of deferred issuance costs		295,762
Issuance of collateralized borrowings, net of deferred issuance costs	29,907
Earnings distributions	(68,304)	(41,154)
Redemption and repurchase of limited partnership interests	(24,156)	(20,896)
Dividends to stockholders	(96,510)	(81,910)
Repurchase of Class A common stock	(10,590)	(69,730)
Cancellation of restricted stock units in satisfaction of withholding tax requirements	(52)	(30)
Proceeds from issuance of Class A common stock, net of costs		14,961
Deemed contribution due to acquisition of Lucera		10,145
Proceeds from exercise of stock options		86
Proceeds from short-term borrowings	150,000
Loans to related parties	(150,000)
Payments on acquistions earn-outs	(10,509)	(4,852)
Net cash provided by (used in) financing activities	(183,737)	98,982
Effect of exchange rate changes on cash and cash equivalents	2,779	2,869
Net (decrease) increase in cash and cash equivalents	(39,982)	(25,900)
Cash and cash equivalents at beginning of period	502,024	462,134
Cash and cash equivalents at end of period	462,042	436,234
Supplemental cash information:
Cash paid during the period for taxes	20,758	35,811
Cash paid during the period for interest	33,204	27,999
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	56,443	28,435
Issuance of Class A and contingent Class A common stock and limited partnership interests for acquisitions	$ 4,225	$ 1,846