Class of Warrant or Right, Repurchases During Period, Shares

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- Definition

Class of Warrant or Right, Repurchases During Period, Value

+ References

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Disposal Group, Sale Period

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- Definition

Proceeds from Divestiture of Business Related to Tax Benefits

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Related Party Transactions, Number of Directors

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Sale of Stock, Number of Shares Exchanged in Transaction

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Sale of Stock, Number of Shares Retained in Transaction, Portion of Transaction Costs

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Stock Repurchase Program, Fees

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No definition available.

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- Definition

Number of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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-Paragraph 3
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- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

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No definition available.

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- Definition

Amount of gain (loss) on sale or disposal of an equity method investment.

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No definition available.

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- Definition

Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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No definition available.

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- Definition

Amount of fees earned from providing investment advice and research to customers.

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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No definition available.

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- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Amount of cash inflow from the sale of investments classified as other.

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- Definition

A fee charged for services from professionals such as doctors, lawyers and accountants. The term is often expanded to include other professions, for example, pharmacists charging to maintain a medicinal profile of a client or customer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Price of a single share of a number of saleable stocks of a company.

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No definition available.

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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- Definition

The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value.

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-Name Accounting Standards Codification
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Related Parties - Additional Information (Details) $ / shares in Units, shares in Thousands, $ in Thousands				1 Months Ended			3 Months Ended				12 Months Ended
	Dec. 29, 2015 USD ($)	Nov. 11, 2015 USD ($) shares	Nov. 04, 2015 USD ($) $ / shares shares	Nov. 30, 2016 USD ($) shares	Mar. 31, 2016 USD ($)	Mar. 31, 2015	Dec. 31, 2016 USD ($) shares	Jun. 30, 2016 USD ($) director $ / shares shares	Dec. 31, 2015 USD ($) shares	Sep. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Jun. 02, 2015 $ / shares	Mar. 13, 2015	Mar. 10, 2015 USD ($)
Related Party Transaction [Line Items]
First annual payment received from the sale											$ 6,552	$ 360,928	$ 0
Professional fees											19,827	27,055	25,596
Total Purchase Price											$ 91,240	$ 63,194	111,585
Warrants repurchased (in shares) \| shares									2,600		15,350
Warrants repurchased									$ 4,400		$ 35,100
Warrants received (in shares) \| shares							6,182		21,605		6,182	21,605
Senior Secured Notes \| 6.875% Senior Secured Notes
Related Party Transaction [Line Items]
Interest rate (percent)							6.875%	6.875%	6.875%		6.875%	6.875%			6.875%	6.875%
Other Assets \| Senior Secured Notes \| 6.875% Senior Secured Notes
Related Party Transaction [Line Items]
Deferred debt costs																$ 12,600
KCG Hotspot
Related Party Transaction [Line Items]
Proceeds related to tax sharing arrangement												$ 70,000
Sale period						3 years						3 years
First annual payment received from the sale					$ 6,600
KCG Hotspot \| Other Assets
Related Party Transaction [Line Items]
Additional consideration, fair value							$ 60,500				$ 60,500
Investment Income and Other, Net \| KCG Hotspot
Related Party Transaction [Line Items]
Gain from sale of business												$ 385,000
BATS \| Investment Income and Other, Net
Related Party Transaction [Line Items]
Pre-tax gain from sale of investment											$ 364,400
Aperture Holdings, LP
Related Party Transaction [Line Items]
Proceeds from Sale of Other Investments	$ 28,500
Aperture Holdings, LP \| Investment income and other, net
Related Party Transaction [Line Items]
Pre-tax gain from sale of investment	$ 10,500											10,500
Modified Dutch Auction Tender Offer
Related Party Transaction [Line Items]
Professional fees												$ 2,100
Common Class A
Related Party Transaction [Line Items]
Number of Shares Purchased \| shares											5,500	3,500
Total Purchase Price											$ 70,700	$ 41,700
Common Class A \| Modified Dutch Auction Tender Offer
Related Party Transaction [Line Items]
Average price per share (in dollars per share) \| $ / shares														$ 14.00
Related Parties
Related Party Transaction [Line Items]
Financing and advisory fees											41	16,800
Professional fees											0	5,507	$ 0
Related Parties \| Other Assets
Related Party Transaction [Line Items]
Deferred debt costs									$ 11,300			11,300
Related Parties \| Treasury Stock
Related Party Transaction [Line Items]
Stock buyback program fees											$ 72	31
Related Parties \| Professional Fees
Related Party Transaction [Line Items]
Professional fees												$ 5,500
Related Parties \| Common Class A
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners (more than)							10.00%				10.00%
Affiliated Entity with Former Directors
Related Party Transaction [Line Items]
Warrants repurchased (in shares) \| shares								6,600
Warrants repurchased								$ 14,200
Number of directors \| director								2
Affiliated Entity with Former Directors \| Common Class A
Related Party Transaction [Line Items]
Number of Shares Purchased \| shares								1,900
Total Purchase Price								$ 26,100
Average price per share (in dollars per share) \| $ / shares								$ 13.48
Serenity Investments, LLC
Related Party Transaction [Line Items]
Total Purchase Price			$ 24,500
Serenity Investments, LLC \| Common Class A
Related Party Transaction [Line Items]
Number of Shares Purchased \| shares			1,900
Average price per share (in dollars per share) \| $ / shares			$ 12.89
Daniel Tierney and related entities
Related Party Transaction [Line Items]
Warrants repurchased (in shares) \| shares		2,000
Warrants repurchased		$ 3,600
JV \| Write-down of Assets and Other Real Estate Charges
Related Party Transaction [Line Items]
Tangible Asset Impairment Charges										$ 4,300
Swap Transaction
Related Party Transaction [Line Items]
Pre-tax gain from sale of investment											$ 331,000
Warrants received (in shares) \| shares				8,100
Portion of transaction costs (in shares) \| shares				46
Swap Transaction \| BATS
Related Party Transaction [Line Items]
Number of shares exchanged in transaction \| shares				8,900
Swap Transaction \| Jefferies LLC
Related Party Transaction [Line Items]
Payments of stock issuance costs				$ 2,900
General Atlantic
Related Party Transaction [Line Items]
Warrants repurchased (in shares) \| shares											7,000
General Atlantic \| Swap Transaction \| Common Class A
Related Party Transaction [Line Items]
Number of shares exchanged in transaction \| shares				18,700			18,700