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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, 2021 | Dec. 31, 2020
Commodities |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative instruments, gain (loss) recognized in income, net | $ 47.7 | $ 4.2
Foreign exchange |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative instruments, gain (loss) recognized in income, net | 35.8 | 36.0
Interest rate, equities, and indices |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative instruments, gain (loss) recognized in income, net | 25.4 | 12.6
TBA and forward settling securities |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative instruments, gain (loss) recognized in income, net | (2.1) | (8.5)
Derivatives |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative instruments, gain (loss) recognized in income, net | $ 106.8 | $ 44.3

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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=125515794&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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