v3.25.4
Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Balance $ 1,893,924 $ 1,862,624
Other comprehensive income (loss) 0 42,421
Balance 1,900,965 1,914,277
Other Comprehensive Income (Loss), Tax 6,224 5,964
Unrealized gain (losses) on securities available for sale    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Balance (16,590) (21,059)
Other comprehensive loss before reclassifications, net of tax 1,845 (5,503)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax 0 0
Other comprehensive income (loss) 1,845 (5,503)
Balance (14,745) (26,562)
Other Comprehensive Income (Loss), Tax 432 (1,634)
Defined Benefit Plan    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Balance (3,609) (3,435)
Other comprehensive loss before reclassifications, net of tax 56 0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax 0 0
Other comprehensive income (loss) 56 0
Balance (3,553) (3,435)
Other Comprehensive Income (Loss), Tax (56) 0
Defined Benefit Plan | Reclassification out of Accumulated Other Comprehensive Income    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Other Comprehensive Income (Loss), Tax 0 0
Total    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Balance (21,231) (15,608)
Other comprehensive loss before reclassifications, net of tax 5,038 53,841
Amounts reclassified from accumulated other comprehensive income (loss), net of tax (5,038) (11,420)
Other comprehensive income (loss) 0 42,421
Balance (21,231) 26,813
Other Comprehensive Income (Loss), Tax (215) 12,597
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Balance (1,032) 8,886
Other comprehensive loss before reclassifications, net of tax 3,137 59,344
Amounts reclassified from accumulated other comprehensive income (loss), net of tax (5,038) (11,420)
Other comprehensive income (loss) (1,901) 47,924
Balance (2,933) 56,810
Other Comprehensive Income (Loss), Tax (591) 14,231
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Reclassification out of Accumulated Other Comprehensive Income    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Other Comprehensive Income (Loss), Tax $ (1,543) $ (3,392)