XML 81 R61.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Assets and Liabilities, at Fair Value - Available for Sale Securities in OCI (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Sep. 30, 2017
--- | --- | ---
Assets and Liabilities, at Fair Value [Abstract] |  |
Equity Investments in Exchange Stock - Cost | $ 3.7 | $ 3.9
Equity Investments in Exchange Stock - Fair Value | $ 10.2 | $ 8.3

X
- Definition Assets and Liabilities, at Fair Value [Abstract] + References No definition available. + Details
Name: | intl_AssetsAndLiabilitiesAtFairValueAbstract
Namespace Prefix: | intl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity Investments in Exchange Stock - Cost + References No definition available. + Details
Name: | intl_EquityInvestmentsInExchangeStockCost
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Equity Investments in Exchange Stock - Fair Value + References No definition available. + Details
Name: | intl_EquityInvestmentsInExchangeStockFairValue
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant