Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from Operating Activities:
Net (loss) income	$ (25,918)	$ 91,570	$ 50,892
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	43,523	44,151	49,384
Deferred income tax (benefit) expense	(15,755)	12,912	(4,979)
Provision for doubtful accounts	67	496	(801)
Non-cash share based compensation	25,620	16,667	15,359
Gain on sale of investment research operations	(21)	(107,699)
Changes in operating assets and liabilities:
Cash restricted or segregated under regulations and other	(3,048)	55	(616)
Deposits with clearing organizations	1,420	(1,113)	38,347
Securities owned, at fair value	3,048	5,973	(5,489)
Receivables from brokers, dealers and clearing organizations	871,317	(404,818)	211,491
Receivables from customers	(11,738)	53,909	(37,238)
Accounts payable and accrued expenses	13,034	(18,978)	27,389
Payables to brokers, dealers and clearing organizations	(853,923)	366,462	(203,805)
Payables to customers	2,681	(775)	(5,075)
Securities sold, not yet purchased, at fair value	(2,397)	(5,102)	6,162
Income taxes receivable/payable	(11,889)	1,710	6,194
Excess tax benefit from share-based payment arrangements	(880)	(2,982)	(1,278)
Other, net	(59)	(3,692)	(3,397)
Net cash provided by operating activities	35,082	48,746	142,540
Cash flows from Investing Activities:
Proceeds from sale of investment research operations, net of deal costs	6,125	111,240
Investment in unconsolidated affiliates			(2,669)
Acquisition of subsidiaries, net of acquired cash			(18,293)
Capital purchases	(21,315)	(11,905)	(13,798)
Capitalization of software development costs	(24,617)	(26,003)	(26,331)
Net cash used in investing activities	(39,807)	73,332	(61,091)
Cash flows from Financing Activities:
Repayments of long term debt	(6,200)	(8,820)	(12,551)
(Repayments of) proceeds from borrowing under short-term bank loans	(9,784)	3,573	4,821
Debt issuance costs	(810)		(1,200)
Excess tax benefit from share-based payment arrangements	880	2,982	1,278
Common stock issued	3,743	1,742	96
Common stock repurchased	(22,112)	(42,046)	(48,165)
Dividends paid	(9,124)	(7,030)
Shares withheld for net settlements of share-based awards	(6,795)	(8,978)	(6,231)
Net cash used in financing activities	(50,202)	(58,577)	(61,952)
Effect of exchange rate changes on cash and cash equivalents	2,251	(8,058)	(6,184)
Net increase (decrease) in cash and cash equivalents	(52,676)	55,443	13,313
Cash and cash equivalents - beginning of year	330,653	275,210	261,897
Cash and cash equivalents - end of period	277,977	330,653	275,210
Supplemental cash flow information:
Interest paid	6,116	3,607	3,979
Income taxes paid	$ 9,880	15,098	$ 11,909
Supplemental disclosure of non-cash investing and financing activities:
Capital expenditures funded by financing from seller		$ 3,606