v3.25.1
Securities (Amortized Cost, Estimated Fair Value, and Gross Unrealized Gains and Losses of AFS and HTM Securities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost $ 941,585 $ 829,852
Available-for-sale Securities, Gross Unrealized Gains 20,774 27,113
Available-for-sale Securities, Gross Unrealized Losses 942 699
Available-for-sale Securities, Estimated Fair Value 961,417 856,266
MBS [Member]    
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost 867,585 756,775
Available-for-sale Securities, Gross Unrealized Gains 20,735 26,885
Available-for-sale Securities, Gross Unrealized Losses 565 87
Available-for-sale Securities, Estimated Fair Value 887,755 783,573
GSE Debentures [Member]    
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost 70,000 69,077
Available-for-sale Securities, Gross Unrealized Gains 39 228
Available-for-sale Securities, Gross Unrealized Losses 41 0
Available-for-sale Securities, Estimated Fair Value 69,998 69,305
Corporate Bonds [Member]    
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost 4,000 4,000
Available-for-sale Securities, Gross Unrealized Gains 0 0
Available-for-sale Securities, Gross Unrealized Losses 336 612
Available-for-sale Securities, Estimated Fair Value $ 3,664 $ 3,388