Loans - Aging Analysis of Loan Modifications (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modified [Line Items]
Accumulated modifications	$ 7,673	$ 14,777
Current
Financing Receivable, Modified [Line Items]
Accumulated modifications	1,936	888
30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	197	479
90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	2,851	0
Non-Accrual
Financing Receivable, Modified [Line Items]
Accumulated modifications	2,689	13,410
Commercial mortgage
Financing Receivable, Modified [Line Items]
Accumulated modifications	1,731	681
Commercial mortgage | Current
Financing Receivable, Modified [Line Items]
Accumulated modifications	1,731	0
Commercial mortgage | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	0	0
Commercial mortgage | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	0	0
Commercial mortgage | Non-Accrual
Financing Receivable, Modified [Line Items]
Accumulated modifications	0	681
Home equity and lines of credit
Financing Receivable, Modified [Line Items]
Accumulated modifications	197
Home equity and lines of credit | Current
Financing Receivable, Modified [Line Items]
Accumulated modifications	0
Home equity and lines of credit | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	197
Home equity and lines of credit | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	0
Home equity and lines of credit | Non-Accrual
Financing Receivable, Modified [Line Items]
Accumulated modifications	0
Commercial and industrial
Financing Receivable, Modified [Line Items]
Accumulated modifications	5,745	14,096
Commercial and industrial | Current
Financing Receivable, Modified [Line Items]
Accumulated modifications	205	888
Commercial and industrial | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	0	479
Commercial and industrial | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Accumulated modifications	2,851	0
Commercial and industrial | Non-Accrual
Financing Receivable, Modified [Line Items]
Accumulated modifications	$ 2,689	$ 12,729