Derivative Instruments (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Jun. 30, 2025	Sep. 30, 2024
Designated as Hedging Instrument \| Cash Flow Hedge \| Interest Rate Swap
Derivatives, Fair Value [Line Items]
Notional Amount	$ 3,650,000	$ 3,650,000
Swap weighted average terms	2 years 8 months 12 days	3 years 1 month 6 days
Swap weighted average interest rate	3.26%	3.10%
Designated as Hedging Instrument \| Cash Flow Hedge \| Interest Rate Swap \| Other Assets
Derivatives, Fair Value [Line Items]
Notional Amount	$ 2,125,000	$ 2,075,000
Swap weighted average terms	2 years 2 months 12 days	2 years 3 months 18 days
Swap weighted average interest rate	2.93%	2.68%
Designated as Hedging Instrument \| Cash Flow Hedge \| Interest Rate Swap \| Other Liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	$ 1,525,000	$ 1,575,000
Swap weighted average terms	3 years 3 months 18 days	4 years 1 month 6 days
Swap weighted average interest rate	3.72%	3.67%
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	$ 85,737	$ 28,878
Derivative, Fair Value, Net	437	323
Not Designated as Hedging Instrument \| Interest Rate Lock Commitments \| Other Assets
Derivatives, Fair Value [Line Items]
Notional Amount	35,917	11,467
Derivative, Fair Value, Net	597	395
Not Designated as Hedging Instrument \| Forward Commitments For Sale Of Mortgage Loans \| Other Liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	49,820	17,411
Derivative, Fair Value, Net	$ (160)	$ (72)