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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 | 3 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Commodity Contract [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ 8.1 | $ 7.7
Foreign Exchange Forward [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | 1.9 | 2.3
Equity [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (3.3) | 0.0
Interest Rate Contract [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | 0.0 | 0.4
TBA and forward settling securities [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | (9.3) | (0.4)
Derivative [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ (2.6) | $ 10.0

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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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