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Loans - Amortized Cost of Nonaccrual Loans by Portfolio Class of Loans (Detail) - USD ($) $ in Thousands | Jun. 30, 2023 | Dec. 31, 2022 | Jun. 30, 2022
--- | --- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | $ 4,689 | $ 5,247
Consumer Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | 612 |
Agricultural Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | 1,921 |
Agricultural [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | 152 |
Commercial Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | 903 |
Commercial and Industrial [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | 1,096 |
Consumer [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans |  | $ 5 |
Nonaccrual With No Allowance For Credit Loss [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | $ 5,241 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Consumer Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 808 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Agricultural Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 3,964 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Agricultural [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 56 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Commercial Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 248 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Commercial and Industrial [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 97 |  |
Nonaccrual With No Allowance For Credit Loss [Member] | Consumer [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 68 |  |
Nonaccrual [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 6,295 |  |
Nonaccrual [Member] | Consumer Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 1,025 |  |
Nonaccrual [Member] | Agricultural Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 3,964 |  |
Nonaccrual [Member] | Agricultural [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 56 |  |
Nonaccrual [Member] | Commercial Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 248 |  |
Nonaccrual [Member] | Commercial and Industrial [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | 934 |  |
Nonaccrual [Member] | Consumer [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Investment in nonaccrual loans | $ 68 |  |

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