Loans Receivable and Allowance for Loan Losses: Narrative (Details) - USD ($)	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	85.00%
Allowance for credit losses	$ 17,478,000	$ 15,817,000
ACL on loans increase	1,661,000
Provision for credit losses - loans	1,254,000	2,132,000	$ 270,000
Adjustment to opening balance	461,000
Nonaccrual loans	1,825,000
Non-accrual loans, ACL	506,000
Non-accrual loans with no ACL	$ 2,060,000
Troubled debt restructured loan		2,500,000
Mortgage loans, one-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	85.00%
Provision for credit losses - loans	$ 580,000	759,000	504,000
Ratio of loans to appraised value, private mortgage insurance requirement, percentage limit	80.00%
Mortgage loans, commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	80.00%
Mortgage loans, land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	65.00%
Provision for credit losses - loans	$ 69,000	$ 9,000	$ (73,000)

Debt Securities, Held-to-Maturity, Allowance For Credit Loss, Excluding Accrued Interest, Adjustment

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Amount, excluding accrued interest, of increase (decrease) in allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

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Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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