Basis of Presentation and Consolidation Level 4 (Details)	9 Months Ended
Jun. 30, 2012
Basis of Presentation and Consolidation (Reclassifications) [Abstract]
Number of different types of foreign currencies	130
Number of customers company-wide	20,000

Number of different types of foreign currencies the company trades

No definition available.

Name:	intl_NumberOfDifferentTypesOfForeignCurrencies
Namespace Prefix:	intl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration