Organization and Basis of Presentation (Details)	Mar. 31, 2012
Organization and Basis of Presentation
Threshold percentage for goodwill impairment testing	50.00%

Represents the threshold percentage of likelihood of fair value of reporting unit being less than carrying amount to be considered for goodwill impairment testing.

No definition available.

Name:	itg_ThresholdPercentageForGoodwillImpairmentTesting
Namespace Prefix:	itg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant