Fair Value - Schedule of Carrying Value and Fair Value for Certain Financial Instruments not Required to be Measured and Reported at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Financial assets:
Investment securities held to maturity	$ 55,345	$ 21,249
Loans receivable, net	14,300	15,100
Carrying Value [Member]
Financial assets:
Investment securities held to maturity	55,747	21,483
Loans receivable, net	1,339,301	1,340,853
Mortgage servicing rights	833	763
Financial liabilities:
Deposits	1,634,734	1,636,115
Estimated Fair Value [Member]
Financial assets:
Investment securities held to maturity	53,089	21,249
Loans receivable, net	1,344,491	1,353,420
Mortgage servicing rights	1,130	998
Financial liabilities:
Deposits	1,631,274	1,635,851
Estimated Fair Value [Member] \| Level 1 [Member]
Financial liabilities:
Deposits	1,435,081	1,426,191
Estimated Fair Value [Member] \| Level 3 [Member]
Financial assets:
Investment securities held to maturity	53,089	21,249
Loans receivable, net	1,344,491	1,353,420
Mortgage servicing rights	1,130	998
Financial liabilities:
Deposits	$ 196,193	$ 209,660

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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- References

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=125521744&loc=d3e122739-111746

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-Name Accounting Standards Codification
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