Fair Value Of Financial Instruments (Schedule Of Fair Value Assets Measured On A Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	$ 1,444,867	$ 1,563,307
MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	964,719	1,088,624
GSE Debentures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	475,759	469,827
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	3,377	3,695
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	1,012	1,161
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	1,444,867	1,563,307
Interest rate swaps	12,369	12,547
Assets	1,457,236	1,575,854
Fair Value, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Interest rate swaps	0	0
Assets	0	0
Fair Value, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	1,444,867	1,563,307
Interest rate swaps	12,369	12,547
Assets	1,457,236	1,575,854
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Interest rate swaps	0	0
Assets	0	0
Fair Value, Recurring [Member] | MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	964,719	1,088,624
Fair Value, Recurring [Member] | MBS [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | MBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	964,719	1,088,624
Fair Value, Recurring [Member] | MBS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | GSE Debentures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	475,759	469,827
Fair Value, Recurring [Member] | GSE Debentures [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | GSE Debentures [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	475,759	469,827
Fair Value, Recurring [Member] | GSE Debentures [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	3,377	3,695
Fair Value, Recurring [Member] | Corporate Bonds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	3,377	3,695
Fair Value, Recurring [Member] | Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	1,012	1,161
Fair Value, Recurring [Member] | Municipal Bonds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	0	0
Fair Value, Recurring [Member] | Municipal Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	1,012	1,161
Fair Value, Recurring [Member] | Municipal Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities	$ 0	$ 0