XML 61 R49.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) number in Millions | Jun. 30, 2018 | Sep. 30, 2017
--- | --- | ---
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract] |  |
Derivative, Number of Instruments Held | 9.7 | 6.1

X
- Definition Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract] + References No definition available. + Details
Name: | intl_FinancialInstrumentsWithOffBalanceSheetRiskAndConcentrationsOfCreditRiskAbstract
Namespace Prefix: | intl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959 + Details
Name: | us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant