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Loans (Tier Risk Rating System) - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2024 | Mar. 31, 2024 | Jun. 30, 2023 | Mar. 31, 2023 | Jun. 30, 2024 | Dec. 31, 2023
Nonaccrual [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Interest income on nonaccrual loans | $ 19 | $ 22 | $ 74 | $ 53 |  |
Nonaccrual [Member] | Agricultural Real Estate [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Decrease in nonaccrual loans due to two borrower relationships |  |  |  |  | $ 15,900 | $ 4,400
Minimum [Member] |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Repayment period of loan with a reasonable reduction of principal balance |  |  |  |  | 2 years |

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