Servicing - Additional Information (Detail) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($) Loan Strata	Sep. 30, 2025 USD ($) Loan Strata	Dec. 31, 2025 USD ($)
Customer Securities for which Entity has Right to Sell or Repledge (Including Securities Sold or Repledged) [Line Items]
Valuation allowance	$ 1,400		$ 883
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	370,000	$ 362,800	362,600
Capitalized service right assets included in other assets	3,900	3,600	3,600
Fair value of the capitalized servicing rights	$ 4,100	$ 4,700	$ 4,500
Number of loans \| Loan	3,578	3,620
Number of strata which included loan \| Strata	3	2
Prepayment rate	11.00%	8.70%	9.80%
Fair value of impairment expense	$ 5
Discount yield	6.47%	5.43%
Valuation allowance	$ 10	$ 5	$ 5
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	173,100	152,300	153,400
Capitalized service right assets included in other assets	2,500	2,400	2,400
Fair value of the capitalized servicing rights	$ 1,100	$ 2,000	$ 1,500
Number of loans \| Loan	677
Number of strata which included loan \| Strata	14	14
Prepayment rate	1.761%	0.715%	1.054%
Fair value of impairment expense	$ 145
Discount yield	8.20%	8.16%
Valuation allowance	$ 1,400	$ 454
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
Three 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	1,003
Fourteen Agricultural 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		652

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

Fair value of impairment expense.

+ 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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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/2003/role/disclosureRef
-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/2003/role/disclosureRef
-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/2009/role/commonPracticeRef
-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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