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Fair Value of Financial Instruments - Changes in the Level 3 Fair Value Category of Unobservable Inputs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
State and Local Governments Tax-Exempt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,188	$ 2,071
Change in Fair Value	$ (2)	$ 9
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Payments, Maturities & Calls	$ (665)	$ (245)
Ending Balance	521	1,835
State and Local Governments Taxable[Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,272	1,274
Change in Fair Value	$ 2	$ 31
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Ending Balance	$ 1,274	$ 1,305
State and Local Governments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 2,460	3,345
Change in Fair Value		$ 40
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Payments, Maturities & Calls	$ (665)	$ (245)
Ending Balance	$ 1,795	$ 3,140

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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.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-SubTopic 10
-Topic 820
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Indicates line item in statement in which net income is reported that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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