CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income before attribution to non-controlling stockholders	$ (9,644)	$ (2,565)	$ 25,919
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	36,624	38,943	34,431
Share-based compensation	32,404	32,772	26,674
Tax expense related to share-based compensation	2,213	1,764	2,042
Amortization of prepaid bonuses and forgivable loans	26,549	33,652	25,707
Benefit from deferred taxes	(3,311)	(4,866)	(22,632)
(Gains) losses on foreign exchange derivative contracts, net	(2,011)	415	(3,529)
(Gains) losses from equity method investments, net	(575)	(1,223)	29
Amortization of loan fees	2,175	1,709	939
Provision for doubtful accounts	319	250	(829)
Loss on disposal of fixed assets	155	590	121
Impairment of investments	5,362	8,829
Mark-to-market of future purchase commitment	(9,545)	(6,941)	(200)
Mark-to-market of equity warrants	2,475
Gain on remeasurement of previously held equity interest	215		(3,695)
Other non-cash charges, net	269	(617)	(358)
(Increase) decrease in operating assets:
Cash and securities segregated under federal and other regulations	(26,572)	12,171	(16,841)
Commissions receivable	20,726	7,847	4,222
Receivables from brokers, dealers and clearing organizations	(9,068)	18,862	(56,116)
Other assets	(46,515)	(44,956)	(34,368)
Increase (decrease) in operating liabilities:
Accrued compensation	(47,894)	14,554	6,069
Accounts payable and accrued expenses	(19,881)	(8,125)	(10,473)
Payables to brokers, dealers and clearing organizations	75,406	(82,889)	104,287
Payables to clearing services customers	18,718	(5,044)	9,345
Other liabilities	71	(10,553)	5,362
Cash provided by operating activities	48,665	4,579	96,106
CASH FLOWS FROM INVESTING ACTIVITIES:
Business acquisitions, net of cash acquired, and purchases of intangible and other assets		(3,300)	(28,655)
Proceeds from other investments	1,106	1,062	662
Proceeds from notes receivable		882	1,000
Purchases of other investments	(3,121)	(11,300)	(24,647)
Purchase of property, equipment and leasehold improvements	(5,907)	(10,694)	(8,536)
Payments for internally developed software	(11,394)	(12,663)	(4,678)
Proceeds on foreign exchange derivative contracts	6,480	5,893	13,575
Payments on foreign exchange derivative contracts	(2,669)	(11,172)	(6,695)
Issuance of notes receivable		(4,953)	(800)
Cash used in investing activities	(15,505)	(46,245)	(58,774)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from short-term borrowings	195,000	55,000	60,000
Repayments of short-term borrowings	(195,000)	(190,000)	(40,000)
Proceeds from long-term obligations		250,000
Repayment of long-term obligations		(60,000)
Purchases of treasury stock	(12,939)	(35,868)	(22,609)
Cash dividends paid to common stockholders	(29,566)	(24,180)	(54,658)
Payment of debt issuance costs	(134)	(8,891)	(2,719)
Proceeds from exercises of stock options	30	75	645
Cash paid for taxes on vested restricted stock units	(9,479)	(9,102)	(6,724)
Payment of contingent consideration liabilities	(769)	(1,693)
Tax expense related to share-based compensation	(2,213)	(1,764)	(2,042)
Cash used in financing activities	(55,070)	(26,423)	(68,107)
Effects of exchange rate changes on cash and cash equivalents	3,472	93	2,271
DECREASE IN CASH AND CASH EQUIVALENTS	(18,438)	(67,996)	(28,504)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	245,879	313,875	342,379
CASH AND CASH EQUIVALENTS, END OF PERIOD	227,441	245,879	313,875
SUPPLEMENTAL DISCLOSURE:
Cash paid for interest	25,240	17,525	11,391
Cash paid for income taxes	15,024	23,948	23,998
Cash received from income tax refunds	2,131	8,539	4,491
Non-Cash Investing and Financing Activities:
Issuance (cancellation) of common stock in connection with an equity method investment, value		(1,084)	1,627
Issuance (cancellation) of common stock in connection with an equity method investment (in shares)		(276,625)	414,938
Business combinations, Other liabilities			20,604
Business combinations, common stock, shares issued value			20,088
Business combinations, common stock, shares issued (in shares)			3,492,095
Business combinations, common stock, contingently issuable value			$ 15,558
Business combinations, common stock, contingently issuable shares (in shares)			3,682,916