v3.26.1
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Schedule of Income Statement Effects of Derivative Instruments (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Derivative Instruments and Hedging Activities Disclosure [Line Items]        
Total derivatives designated as hedging instruments $ 69.2 $ 184.5 $ 373.3 $ 506.3
Derivative contracts designated as hedging instruments        
Derivative Instruments and Hedging Activities Disclosure [Line Items]        
Total derivatives designated as hedging instruments (2.2) 6.1 2.3 9.1
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 22.7 33.5 74.1 83.4
Interest rate contracts | Derivative contracts designated as hedging instruments        
Derivative Instruments and Hedging Activities Disclosure [Line Items]        
Total derivatives designated as hedging instruments (1.2) 0.0 (3.4) (0.2)
Foreign currency forward contracts        
Derivative Instruments and Hedging Activities Disclosure [Line Items]        
Total derivatives designated as hedging instruments 11.7 39.3 48.4 106.4
Foreign currency forward contracts | Derivative contracts designated as hedging instruments        
Derivative Instruments and Hedging Activities Disclosure [Line Items]        
Total derivatives designated as hedging instruments $ (1.0) $ 6.1 $ 5.7 $ 9.3