Derivative Instruments (Schedule Of Effect Of Derivative Instruments, Gain (Loss) In Statement Of Financial Performance) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Designated as Hedging Instrument | Cash Flow Hedging | Interest Expense: Borrowed Funds and Deposits
Derivatives, Fair Value [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 46,503	$ 88,354	$ 59,821
Designated as Hedging Instrument | Cash Flow Hedging | Other Comprehensive Income (Loss)
Derivatives, Fair Value [Line Items]
Amount of gain/(loss) recognized	$ 33,639	$ (75,900)	$ 146,807
Not Designated as Hedging Instrument | Interest Rate Lock Commitments
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other Operating Income	Noninterest Income, Other Operating Income	Noninterest Income, Other Operating Income
Total	$ (123)	$ 395	$ 332
Not Designated as Hedging Instrument | Forward Commitments For Sale Of Mortgage Loans
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net gain on the sale of loans	Net gain on the sale of loans	Net gain on the sale of loans
Total	$ (279)	$ (72)	$ 11