Name:	itg_BusinessAcquisitionPurchasePriceAllocationCurrentLiabilitiesAccountsPayableAndAccruedLiabilities
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of acquisition cost of a business combination allocated to customer related intangible assets of the acquired entity.

No definition available.

Name:	itg_BusinessAcquisitionPurchasePriceAllocationCustomerRelatedIntangibleAssets
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the number of years over which the goodwill is deductible for tax purposes.

No definition available.

Name:	itg_BusinessAcquisitionPurchasePriceAllocationGoodwillNumberOfYearsForExpectedTaxDeductible
Namespace Prefix:	itg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The amount of acquisition cost of a business combination allocated to other assets and liabilities of the acquired entity.

No definition available.

Name:	itg_BusinessAcquisitionPurchasePriceAllocationOtherAssetsLiabilitiesNet
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the costs associated with the termination of distribution agreement with a third party which is included in the acquisition related costs, net of recovery from acquiree's former owners.

No definition available.

Name:	itg_BusinessCombinationAcquisitionTerminationCostsNet
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the portion of costs associated with the termination of distribution agreement with a third party which was subject to recovery from acquiree's former owners.

No definition available.

Name:	itg_BusinessCombinationAcquisitionTerminationCostsPortionCoveredByFormerOwners
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the minimum number of clients served by an entity acquired by the reporting entity.

No definition available.

Name:	itg_MinimumNumberOfClientsOfAcquiredEntity
Namespace Prefix:	itg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Amount of cash paid to acquire the entity.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityCashPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The total purchase price of the acquired entity. This includes cash paid to equity interest holders of the acquired entity, fair value of debt and equity securities issued to equity holders of the acquired entity, and transaction costs paid to third parties to consummate the acquisition.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 35

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationAssetsAcquiredLiabilitiesAssumedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of cash and cash equivalents acquired in a business combination.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentAssetsCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of acquisition cost of a business combination allocated to receivables.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 37

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentAssetsReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of acquisition cost of a business combination allocated to deferred revenue of the acquired entity.

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 01-3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationCurrentLiabilitiesDeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 52

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 53

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e1043-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.