Merger of GETCO and Knight - Assets Acquired and Liabilities Assumed (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Jul. 01, 2013
Identifiable Net Assets
Goodwill	$ 17,311	$ 17,311
Knight [Member]
Identifiable Net Assets
Cash and cash equivalents			509,133
Cash and cash equivalents segregated under federal and other regulations			203,045
Financial instruments owned			1,937,929
Securities borrowed			1,158,981
Receivable from brokers, dealers and clearing organizations			1,369,474
Fixed assets and leasehold improvements			80,280
Investments			106,353
Intangible assets			155,425
Assets within discontinued operations			5,607,063
Deferred tax asset, net			65,465
Other assets			140,933
Total Assets			11,334,081
Financial instruments sold, not yet purchased			1,512,983
Collateralized financings			1,166,211
Payable to brokers, dealers and clearing organizations			635,914
Payable to customers			527,918
Accrued compensation expense			107,409
Accrued expenses and other liabilities			130,010
Liabilities within discontinued operations			5,518,168
Debt			375,000
Total Liabilities			9,973,613
Total identified assets acquired, net of assumed liabilities			1,360,468
Goodwill			12,666
Total Purchase Price			$ 1,373,134