Servicing - Additional Information (Detail) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2025 USD ($) Strata Loan	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Valuation allowance	$ 459		$ 97
1-4 Family Real Estate Loans [Member]
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Loans serviced for others unpaid principal amount	362,800	$ 366,000	364,300
Capitalized service right assets included in other assets	3,600	3,500	3,500
Fair value of the capitalized servicing rights	$ 4,700	$ 5,200	$ 4,800
Prepayment rate	8.70%	7.20%	8.10%
Number of strata which included loan \| Strata	2
Number of loans \| Loan	3,620
Discount yield	5.43%
Valuation allowance	$ 5		$ 2
Agricultural Real Estate Loans [Member]
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Loans serviced for others unpaid principal amount	152,300	$ 140,300	141,900
Capitalized service right assets included in other assets	2,400	2,200	2,200
Fair value of the capitalized servicing rights	$ 2,000	$ 2,700	$ 2,700
Prepayment rate	0.715%	0.156%	0.184%
Number of strata which included loan \| Strata	14
Number of loans \| Loan	652
Discount yield	8.16%
Valuation allowance	$ 454		$ 95
Two 1-4 Family Real Estate Strata [Member]
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Number of loans \| Loan	73

Capitalized service right assets fair market value.

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- Definition

Capitalized service right assets included in other assets.

+ References

No definition available.

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- Definition

Loans serviced for others unpaid principal amount.

+ References

No definition available.

+ Details

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- Definition

Number of Loans

+ References

No definition available.

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- Definition

Number of strata which included loan.

+ References

No definition available.

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

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- Definition

Amount of increase (decrease) in the amortized amount from a decrease (increase) in the valuation allowance applied to the servicing asset for a 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
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(5)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-4

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- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-2

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

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