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Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Schedule of Accumulated Other Comprehensive Income Effects of Derivative Instruments Designated for Hedging Held (Details) - USD ($) $ in Millions | 3 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |
Amount of (Loss)/Gain Recognized in Other Comprehensive Income on Derivatives, net of tax | $ (6.9) | $ 20.7
Interest rate contracts |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |
Amount of (Loss)/Gain Recognized in Other Comprehensive Income on Derivatives, net of tax | 0.1 | 12.6
Foreign currency forward contracts |  |
Derivative Instruments and Hedging Activities Disclosure [Line Items] |  |
Amount of (Loss)/Gain Recognized in Other Comprehensive Income on Derivatives, net of tax | $ (7.0) | $ 8.1

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- Definition Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480627/815-20-45-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 10A -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A + Details
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