Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Accumulated Other Comprehensive Income Effects of Derivative Instruments (Details) $ in Millions	3 Months Ended
	Dec. 31, 2021 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	$ 0.1
Interest Income
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain or Reclassified from Accumulated Other Comprehensive Income into Income	0.1
Interest rate contracts
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	0.1
Interest rate contracts | Interest Income
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain or Reclassified from Accumulated Other Comprehensive Income into Income	$ 0.1