CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities
Net income	$ 137,532	$ 24,556
Loss from discontinued operations, net of tax	784	0
Income from continuing operations, net of tax	138,316	24,556
Adjustments to reconcile income from continuing operations, net of tax to net cash provided by (used in) operating activities
Non-cash gain on Knight Common Stock	(127,972)	0
Deferred tax benefit	(103,499)	0
Depreciation and amortization	36,004	27,180
Stock and unit-based compensation	41,537	10,152
Unrealized gain (loss) on investments	5,625	(12,705)
Writedown of assets and lease loss accrual	4,248	0
Amortization of debt offering costs	2,479	427
Deferred rent	(247)	1,422
Operating activities from discontinued operations	(962)	0
(Increase) decrease in operating assets
Cash and securities segregated under federal and other regulations	(13,397)	0
Financial instruments owned, at fair value	68,827	(503,396)
Securities borrowed	(159,679)	(32,673)
Receivable from brokers, dealers and clearing organizations	179,403	33,235
Other assets	31,059	3,837
Financial instruments sold, not yet purchased, at fair value
Financial instruments sold, not yet purchased, at fair value	137,389	344,087
Securities loaned	(83,440)	0
Financial instruments sold under agreements to repurchase	50,029	0
Payable to brokers, dealers and clearing organizations	6,079	79,226
Payable to customers	(41,782)	0
Accrued compensation expense	12,537	(34,291)
Accrued expenses and other liabilities	(21,988)	(22,184)
Net cash provided by (used in) operating activities	160,566	(81,127)
Cash flows from investing activities
Cash acquired upon acquisition of Knight Capital Group, Inc.	509,133	0
Proceeds and distributions from investments	3,251	19,820
Purchases of investments	(17,506)	(35,631)
Purchases of investments	(85)	(89,689)
Investing activities from discontinued operations	(12,963)	0
Net Cash Provided by (Used in) Investing Activities	507,756	(105,500)
Cash flows from financing activities
Proceeds from issuance of Credit Agreement	535,000	0
Proceeds from Senior Secured Notes	305,000	0
Payment of debt issuance cost	(34,592)	0
Issuance of equity to General Atlantic	55,000	0
Payment to former Knight Capital Group, Inc. stockholders	(720,000)	0
Repayment of Knight Convertible Notes	(257,741)	0
Funding of collateral account for Knight Convertible Notes	(117,259)	0
Borrowings under unsecured credit facility	0	46,750
Borrowings under secured credit facility	25,000	0
Repayment of secured credit facility	(25,000)	0
Repayment of notes	(15,000)	0
Borrowings under capital lease obligations	0	13,758
Principal payments on capital lease obligations	(11,738)	(10,679)
Members' distributions	(21,002)	(47,383)
Cost of common stock repurchased	(9,811)	0
Net cash used in financing activities	(292,143)	2,446
Effect of exchange rate changes on cash and cash equivalents	(5,098)	0
Increase (decrease) in cash and cash equivalents	371,081	(184,181)
Cash and cash equivalents at beginning of period	427,631	607,689
Cash and cash equivalents at end of period	798,712	423,508
Supplemental disclosure of cash flow information:
Cash paid for interest	25,734	6,097
Cash paid for income taxes	$ 9,071	$ 19,932