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Debt - Other Debt and Other Items (Details) - Other Debt - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Unsecured
Debt Instrument [Line Items]
Current borrowing capacity	$ 387.5
Standby Letters of Credit
Debt Instrument [Line Items]
Outstanding standby letters of credit	$ 889.3	$ 934.5

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