XML 104 R84.htm IDEA: XBRL DOCUMENT
v3.20.4

Commitments and Contingencies - Contingencies and Litigation (Details) $ in Millions | Nov. 16, 2018 account | Sep. 30, 2019 USD ($)
--- | --- | ---
Other Commitments [Line Items] |  |
Loss contingency, range of possible loss, portion not accrued |  | $ 29.0
Maximum amount of individual accounts receivable account |  | $ 1.4
StoneX Financial [Member] |  |
Other Commitments [Line Items] |  |
Number of accounts | account | 300 |

X
- Definition Loss Contingency, Individual Accounts Maximum, Receivable + References No definition available. + Details
Name: | intl_LossContingencyIndividualAccountsMaximumReceivable
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number Of Accounts + References No definition available. + Details
Name: | intl_NumberOfAccounts
Namespace Prefix: | intl_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 05 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99385795&loc=d3e12631-108344 + Details
Name: | us-gaap_LossContingencyRangeOfPossibleLossPortionNotAccrued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_OtherCommitmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=intl_StoneXFinancialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |