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Credit Facilities - Number of Credit Facilities (Details) | 12 Months Ended |
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Sep. 30, 2018 USD ($) Rate | May 05, 2015 USD ($)
Line of Credit Facility [Line Items] |  |
Number of credit facilities | 4 |
Line of Credit Facility, Maximum Borrowing Capacity | $ | $ 150.0 |
HCO Syndicated line of credit facility [Member] |  |
Line of Credit Facility [Line Items] |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate | 0.625% |
Line of Credit Facility, Interest Rate at Period End | Rate | 5.17% |
Line of Credit Facility, Maximum Borrowing Capacity | $ | $ 262,000,000 |
HCO Syndicated line of credit facility [Member] | Eurodollar Rate [Member] |  |
Line of Credit Facility [Line Items] |  |
Debt Instrument, Basis Spread on Variable Rate | 3.00% |
HCO Syndicated line of credit facility [Member] | Base Rate [Member] |  |
Line of Credit Facility [Line Items] |  |
Debt Instrument, Basis Spread on Variable Rate | 2.00% |
INTL FCStone, Ltd [Member] |  |
Line of Credit Facility [Line Items] |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ | $ 25,000,000 |
INTL FCStone, Ltd [Member] | Base Rate [Member] |  |
Line of Credit Facility [Line Items] |  |
Debt Instrument, Basis Spread on Variable Rate | 2.50% |
INTL FCStone Financial Margin line of credit facility [Member] |  |
Line of Credit Facility [Line Items] |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate | 0.50% |
Line of Credit Facility, Interest Rate at Period End | Rate | 7.25% |
Line of Credit Facility, Maximum Borrowing Capacity | $ | $ 75,000,000 | $ 75,000,000
INTL FCStone Financial Margin line of credit facility [Member] | Base Rate [Member] |  |
Line of Credit Facility [Line Items] |  |
Debt Instrument, Basis Spread on Variable Rate | 2.00% |

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- Definition Number of credit facilities available to the company. + References No definition available. + Details
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Balance Type: | na
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- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition The effective interest rate at the end of the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- 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
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Balance Type: | credit
Period Type: | instant

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- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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