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Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Income Statement Effects of Derivative Instruments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Designated as Hedging Instrument |  |  |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |  |  |
Total derivatives designated as hedging instruments | $ (2.6) | $ (12.7) | $ (19.4) | $ (29.2)
Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring | 0.0 | 0.0 | 0.0 | 0.0
Interest rate contracts |  |  |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |  |  |
Total derivatives designated as hedging instruments | 27.1 | 51.6 | 70.0 | 85.5
Interest rate contracts | Designated as Hedging Instrument |  |  |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |  |  |
Total derivatives designated as hedging instruments | (4.4) | (14.3) | (24.9) | (31.3)
Foreign currency forward contracts | Designated as Hedging Instrument |  |  |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |  |  |
Total derivatives designated as hedging instruments | $ 1.8 | $ 1.6 | $ 5.5 | $ 2.1

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- Definition Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Before Tax, Forecasted Transaction Not Probable + References No definition available. + Details
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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 -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A + 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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- Details
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- Details
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