Securities - Schedule of Allowance for Credit Losses on Held-to-maturity Securities (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Beginning balance	$ 220
Ending balance	180
ASU 2016-13 [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Beginning balance	220	$ 268
Current period provision	(40)	(43)
Ending balance	180	225
ASU 2016-13 [Member] \| Obligations of State and Political Subdivisions [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Beginning balance	167	174
Current period provision	(22)	(2)
Ending balance	145	172
ASU 2016-13 [Member] \| Corporate Debt Securities [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Beginning balance	53	94
Current period provision	(18)	(41)
Ending balance	$ 35	$ 53

Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

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- Definition

Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 20
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

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