Investment Securities - Additional Information (Detail) - USD ($)	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021
Schedule Of Available For Sale Securities [Line Items]
Realized gross gains		$ 508,000
Proceeds from the sale of investment securities	$ 0	19,700,000
Realized gross losses		48,000
Investment securities available for sale, at fair value	208,647,000	240,581,000
Public Deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available for sale, at fair value	$ 245,500,000	$ 250,400,000
Debt Securities, Available-for-Sale, Pledging Purpose [Extensible Enumeration]	us-gaap:AssetPledgedAsCollateralWithRightMember	us-gaap:AssetPledgedAsCollateralWithRightMember

Realized gross losses on sale of investments.

No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

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- Definition

Indicates pledging purpose of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
-Topic 860
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
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-URI https://asc.fasb.org/extlink&oid=123419778&loc=d3e5710-111685

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- Definition

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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- Definition

The net cash paid (received) associated with the acquisition or disposal of all investments, including securities and other assets.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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