Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income (loss)	$ 691	$ (39,440)	$ (25,918)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Gain on sale of investment research operations			(21)
Depreciation and amortization	43,860	45,153	43,523
Deferred income tax expense (benefit)	570	33,826	(15,755)
Provision for doubtful accounts	593	375	67
Non-cash share-based compensation	29,762	20,238	25,620
Leasehold asset write-off	1,444	7,492
Other intangible asset impairment		325
Gain on investment in joint venture	(608)
Changes in operating assets and liabilities:
Deposits with clearing organizations	(20,047)	8,661	1,420
Securities owned, at fair value	1,248	1,004	3,048
Receivables from brokers, dealers and clearing organizations	(97,543)	(26,701)	871,317
Receivables from customers	(162,725)	(11,832)	(11,738)
Accounts payable and accrued expenses	49,565	(11,292)	13,034
Payables to brokers, dealers and clearing organizations	224,821	7,658	(853,923)
Payables to customers	14,865	7,907	2,681
Securities sold, not yet purchased, at fair value	5	(247)	(2,397)
Income taxes receivable/payable	1,706	2,892	(11,889)
Excess tax benefit from share-based payment arrangements			(880)
Other, net	(19,890)	(339)	(59)
Net cash provided by operating activities	68,317	45,680	38,130
Cash Flows from Investing Activities:
Proceeds from sale of investment research operations, net of deal costs			6,125
Investment in joint ventures	(612)
Capital purchases	(13,801)	(19,402)	(21,315)
Capitalization of software development costs	(27,587)	(27,782)	(24,617)
Net cash used in investing activities	(42,000)	(47,184)	(39,807)
Cash Flows from Financing Activities:
Repayments of long term debt	(1,137)	(3,963)	(6,200)
Proceeds from (repayments of) borrowing under short-term bank loans	(18,628)	29,272	(9,784)
Debt issuance costs	(751)	(762)	(810)
Excess tax benefit from share-based payment arrangements			880
Common stock issued	2,397	1,376	3,743
Common stock repurchased	(5,814)	(16,933)	(22,112)
Dividends paid	(9,165)	(9,156)	(9,124)
Shares withheld for net settlements of share-based awards	(11,011)	(10,779)	(6,795)
Net cash used in financing activities	(44,109)	(10,945)	(50,202)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(6,813)	170	1,704
Net decrease in cash, cash equivalents and restricted cash	(24,605)	(12,279)	(50,175)
Cash, cash equivalents and restricted cash—beginning of period	306,051	318,330	368,505
Cash, cash equivalents and restricted cash—end of period	281,446	306,051	318,330
Supplemental cash flow information:
Interest paid	4,734	4,960	6,116
Income taxes paid, net	6,991	10,515	$ 9,880
Supplemental disclosure of non-cash investing and financing activities:
Investment in joint venture	$ 1,393
Capital expenditures funded by financing from seller		$ 400