Class of Warrant or Right, Repurchases During Period, Shares

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- Definition

Class of Warrant or Right, Repurchases During Period, Value

+ References

No definition available.

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- Definition

Disposal Group, Sale Period

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- Definition

Proceeds from Divestiture of Business Related to Tax Benefits

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No definition available.

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- Definition

Related Party Transaction, Number of Beneficial Owners

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No definition available.

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- Definition

Related Party Transactions, Number of Directors

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No definition available.

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- Definition

Stock Repurchase Program, Fees

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No definition available.

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- Definition

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

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

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.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(a),(d))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

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

+ References

No definition available.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
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-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.2(a),(b),(c),(d))
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-Section 45
-Paragraph 3
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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.

+ References

No definition available.

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- Definition

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

+ References

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
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-Name Accounting Standards Codification
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.3-04)
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

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Related Parties - Additional Information (Details) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended		3 Months Ended			9 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2015	Sep. 30, 2016 USD ($) beneficial_owner shares	Jun. 30, 2016 USD ($) director $ / shares shares	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) beneficial_owner shares	Sep. 30, 2015 USD ($)	Mar. 13, 2015	Mar. 10, 2015 USD ($)
Related Party Transaction [Line Items]
First annual payment received from the sale						$ 6,552	$ 360,928
Professional fees			$ 4,139		$ 4,406	15,497	$ 21,281
Value of stocks repurchased						$ 87,167
Warrants repurchased (in shares) \| shares			300			8,333
Warrants repurchased			$ 700			$ 15,900
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]
Gain from sale of business							$ 373,800
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			$ 59,900			$ 59,900
Investment Income and Other, Net \| KCG Hotspot
Related Party Transaction [Line Items]
Gain from sale of business							$ 385,000
Professional Fees \| KCG Hotspot
Related Party Transaction [Line Items]
Professional fees							6,700
BATS \| Investment Income and Other, Net
Related Party Transaction [Line Items]
Pre-tax gain from sale of investment						33,400
Related Parties
Related Party Transaction [Line Items]
Financing and advisory fees						23	16,800
Professional fees			$ 0		$ 0	0	5,507
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						$ 66
Related Parties \| Professional Fees
Related Party Transaction [Line Items]
Professional fees							$ 5,500
Related Parties \| Common Class A
Related Party Transaction [Line Items]
Number of beneficial owners \| beneficial_owner			1			1
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 repurchased \| shares				1,900
Value of stocks repurchased				$ 26,100
Average price per share (in dollars per share) \| $ / shares				$ 13.48
JV \| Write-down of Assets and Other Real Estate Charges
Related Party Transaction [Line Items]
Tangible Asset Impairment Charges					$ 4,300