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Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Notional Values For Derivatives Instrument (Details) - Designated as Hedging Instrument £ in Millions, zł in Millions, $ in Millions | Mar. 31, 2023 USD ($) | Mar. 31, 2023 PLN (zł) | Mar. 31, 2023 GBP (£) | Sep. 30, 2022 USD ($) | Sep. 30, 2022 PLN (zł) | Sep. 30, 2022 GBP (£)
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Interest rate contracts |  |  |  |  |  |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] |  |  |  |  |  |
Derivative, notional amount | $ 2,000.0 |  |  | $ 1,500.0 |  |
Foreign currency forward contracts | Polish Zloty |  |  |  |  |  |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] |  |  |  |  |  |
Derivative, notional amount | 33.2 | zł 156.1 |  | 0.0 | zł 0.0 |
Foreign currency forward contracts | British Pound Sterling |  |  |  |  |  |
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items] |  |  |  |  |  |
Derivative, notional amount | $ 206.8 |  | £ 168.0 | $ 207.3 |  | £ 168.0

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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 + 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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