Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 15, 2014
Document and Entity Information
Entity Registrant Name	INVESTMENT TECHNOLOGY GROUP, INC.
Entity Central Index Key	0000920424
Document Type	10-Q
Document Period End Date	Sep. 30, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		34,788,970
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3