XML 94 R56.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Description of Business and Significant Accounting Policies - Basis of Presentation and Consolidation (Details) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017
Amount Recognized in Income Due to Inflationary Accounting | $ 3,900,000 | $ 3,400,000 |
Net assets denominated in Argentine Pesos | 5,500,000 | 11,600,000 |
Cash denominated in Argentine Pesos | 100,000 | 1,400,000 |
Fair Value of Exchange Memberships | $ 6,000,000 | $ 6,400,000 |
Preferred Stock, Par or Stated Value Per Share | $ 0.01 |  | $ 0.01
Preferred Stock, Shares Outstanding | 0 | 0 | 0
US Government Securities and Other Securities - Deposits and Receivables | $ 603,814,800 | $ 800,000,000 |
Non-Trading Technology and Support [Member] |  |  |
Prior Period Reclassification Adjustment |  |  | $ 11,600,000
communications [Member] |  |  |
Prior Period Reclassification Adjustment |  |  | $ 5,000,000
Exchange memberships not representing an ownership interest [Member] |  |  |
Memberships in Exchanges Owned | 5,800,000 |  |
Exchange memberships representing an ownership interest [Member] |  |  |
Memberships in Exchanges Owned | $ 5,600,000 |  |

X
- Definition Cash denominated in Argentine Pesos + References No definition available. + Details
Name: | intl_CashdenominatedinArgentinePesos
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value of Exchange Memberships + References No definition available. + Details
Name: | intl_FairValueofExchangeMemberships
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Net assets denominated in Argentine Pesos + References No definition available. + Details
Name: | intl_NetassetsdenominatedinArgentinePesos
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition US Government Securities and Other Securities - Deposits and Receivables + References No definition available. + Details
Name: | intl_USGovernmentSecuritiesandOtherSecuritiesDepositsandReceivables
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount that will be recognized through the income statement (as well as the impact on the other financial statements) as part of highly inflationary accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521 + Details
Name: | us-gaap_AmountRecognizedInIncomeDueToInflationaryAccounting
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of capitalized cost for obtaining membership with right to do business on trading exchange. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 340 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99387790&loc=d3e43427-110978 + Details
Name: | us-gaap_MembershipsInExchangesOwned
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_PreferredStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_PreferredStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of a reclassification adjustment made to prior period financial statement amounts. + References No definition available. + Details
Name: | us-gaap_PriorPeriodReclassificationAdjustment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=intl_NonTradingTechnologyandSupportMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=intl_CommunicationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=intl_ExchangemembershipsnotrepresentinganownershipinterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=intl_ExchangemembershipsrepresentinganownershipinterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |