v3.26.1
Securities (Amortized Cost, Estimated Fair Value, and Gross Unrealized Gains and Losses of AFS and HTM Securities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Sep. 30, 2025
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost $ 795,659 $ 847,369
Available-for-sale Securities, Gross Unrealized Gains 14,642 20,303
Available-for-sale Securities, Gross Unrealized Losses 735 456
Available-for-sale Securities, Estimated Fair Value 809,566 867,216
MBS [Member]    
Marketable Securities [Line Items]    
Available-for-sale Securities, Amortized Cost 791,659 843,369
Available-for-sale Securities, Gross Unrealized Gains 14,642 20,303
Available-for-sale Securities, Gross Unrealized Losses 550 172
Available-for-sale Securities, Estimated Fair Value 805,751 863,500
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 185 284
Available-for-sale Securities, Estimated Fair Value $ 3,815 $ 3,716