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Loans (Impaired Loans) - Additional Information (Detail) | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2025 USD ($) Loan | Jun. 30, 2024 USD ($) Loan | Jun. 30, 2025 USD ($) Contract Loan | Jun. 30, 2024 USD ($) Loan | Dec. 31, 2024 USD ($) | Jan. 01, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Modifications to borrower experiencing financial difficulty | $ 0 | $ 0 | $ 0 | $ 0 |  |
Maximum time for re-evaluation (in months) |  |  | 12 months |  |  |
Re-evaluation period for real estate |  |  | 2 years |  |  |
Unsecured consumer loans, credit card credits and overdraft lines of credit reach |  |  | 90 days |  |  |
Delinquent period for charging down consumer loans |  |  | 90 days |  |  |
Litigation and any deficiency charged off period |  |  | 150 days |  |  |
Delinquent period for charging down/allocated commercial and agricultural credits |  |  | 120 days |  |  |
Number of contracts modified | Loan | 0 | 0 | 0 | 0 |  |
Principal Forgiveness [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Number of contracts modified | Contract |  |  | 0 |  |  |
Consumer Real Estate [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Foreclosed residential real estate property | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 |
Residential real estate properties foreclosure proceedings | $ 925,000 | $ 795,000 | $ 925,000 | $ 795,000 | $ 1,300,000 |
ASU 2016-13 [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Allowance for credit losses on loans and unfunded commitments |  |  |  |  |  | $ 4,500,000
Allowance for credit losses on loans and unfunded commitments net of tax |  |  |  |  |  | $ 3,400,000

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