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
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

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

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