Credit Facilities - Number of Credit Facilities (Details)	Dec. 31, 2015
Credit Facilities [Abstract]
Number of credit facilities	4

Number of credit facilities available to the company.

No definition available.

Name:	intl_NumberOfCreditFacilities
Namespace Prefix:	intl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant