Loans - Classification of Loans (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	$ 1,620,891	$ 1,246,605
Net deferred loan fees and costs	(2,640)	(520)
Total loans	1,623,531	1,247,125
Allowance for loan losses	(12,844)	(8,552)	$ (7,869)
Loans held for investment, net	1,610,687	1,238,573
Servicing of loans to others	246,000	233,200
Loans held for sale	0	0
Amount from sale of loans	80,300	46,600
Net gain on sale of loans held-for-sale(1)	$ 5,143	1,307
PPP Loans
Classification of Loans by Loan Portfolio Segment [Abstract]
Interest rate	1.00%
Amount of loans forgiven	$ 355,900
PPP Loans \| Maximum
Classification of Loans by Loan Portfolio Segment [Abstract]
Loan term	5 years
Extension to loan term	5 years
PPP Loans \| Minimum
Classification of Loans by Loan Portfolio Segment [Abstract]
Loan term	2 years
Residential real estate
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	$ 515,316	444,011
Total loans	516,258	444,140
Allowance for loan losses	(3,951)	(4,155)	(5,103)
Multi-family
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	574,413	266,294
Total loans	575,061	266,714
Allowance for loan losses	(4,308)	(2,433)	(1,506)
Commercial real estate
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	472,511	348,641
Total loans	472,984	348,807
Allowance for loan losses	(3,707)	(1,884)	(1,221)
Commercial and industrial
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	45,758	172,274
Total loans	46,285	172,077
Allowance for loan losses	(761)	(79)	(38)
Commercial and industrial \| PPP Loans
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	10,200	140,400
Construction and land development
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	12,871	15,374
Total loans	12,907	15,374
Allowance for loan losses	(115)
Consumer
Classification of Loans by Loan Portfolio Segment [Abstract]
Gross loans	22	11
Total loans	36	13
Allowance for loan losses	$ (2)	$ (1)	$ (1)

Amount of loans forgiven by the Small Business Administration (SBA).

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Extension period of repayment of financing receivable, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of loans serviced for others.

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Period of time between issuance and maturity of finance receivable, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Contractual interest rate for loans receivable.

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The cash inflow from the sale of loans receivables arising from the financing of goods and services and from the sales of loans held for investment..

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

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Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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