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Loans and Allowance for Credit Losses - Summary of Aging Analysis of Modifications (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Sep. 30, 2024
--- | --- | ---
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | $ 39,563 | $ 34,758
Current | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 21,261 | 27,176
30-59 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 18,056 | 7,475
60-89 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
90+ Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 246 | 107
Commercial loans | Commercial real estate |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 15,044 | 12,482
Commercial loans | Commercial real estate | Current | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 470 | 12,482
Commercial loans | Commercial real estate | 30-59 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 14,574 | 0
Commercial loans | Commercial real estate | 60-89 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Commercial loans | Commercial real estate | 90+ Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Commercial loans | Commercial and industrial |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 24,089 | 21,839
Commercial loans | Commercial and industrial | Current | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 20,607 | 14,364
Commercial loans | Commercial and industrial | 30-59 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 3,482 | 7,475
Commercial loans | Commercial and industrial | 60-89 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Commercial loans | Commercial and industrial | 90+ Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Business banking |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months |  | 107
Business banking | Current | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months |  | 107
Business banking | 30-59 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months |  | 0
Business banking | 60-89 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months |  | 0
Business banking | 90+ Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months |  | 0
Consumer loans | Consumer real estate |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 430 | 330
Consumer loans | Consumer real estate | Current | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 184 | 223
Consumer loans | Consumer real estate | 30-59 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Consumer loans | Consumer real estate | 60-89 Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | 0 | 0
Consumer loans | Consumer real estate | 90+ Days Past Due | Accrual |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Financing receivable, modified, after 12 months | $ 246 | $ 107

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