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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, 2019 | Sep. 30, 2018 | Sep. 30, 2017
Commodity Contract [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ 100.8 | $ 94.0 | $ 47.3
Foreign Exchange Forward [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | 8.1 | 9.2 | 8.7
Interest Rate Contract [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (2.6) | 1.0 | (0.1)
TBA and forward settling securities [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (35.3) | 14.5 | (2.5)
Derivative [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ 71.0 | $ 118.7 | $ 53.4

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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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + 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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