Derivatives and Hedging Activities - Schedule of Impact of Client Swap Program that are Not Designated in Accounting Hedges (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Interest rate contracts | ||||
| Derivative [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | $ 380 | $ 65 | $ 404 | $ 70 |
| Pay fixed/receive floating swap | Other noninterest income | ||||
| Derivative [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | 1,218 | (11,496) | (716) | 8,689 |
| Receive fixed/pay floating swap | Other noninterest income | ||||
| Derivative [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | $ (838) | $ 11,561 | $ 1,120 | $ (8,619) |