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Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions | 12 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Commodity Contract [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ 47.3 | $ 41.8 | $ 78.6
Foreign Exchange Forward [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | 8.7 | 9.7 | 7.5
Interest Rate Contract [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (0.1) | 0.8 | 3.2
TBA and forward settling securities [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (2.5) | (14.4) | (5.1)
Derivative [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ 53.4 | $ 37.9 | $ 84.2

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + 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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