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Loans - Impaired Loans Classified as Troubled Debt Restructured (Detail) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2020 USD ($) Contract | Jun. 30, 2019 USD ($) Contract | Jun. 30, 2020 USD ($) Contract Loan | Jun. 30, 2019 USD ($) Contract | Dec. 31, 2019 Loan
Financing Receivable Modifications [Line Items] |  |  |  |  |
Number of Contracts Modified in the Last three Months | Loan |  |  | 5 |  | 4
Commercial Real Estate [Member] |  |  |  |  |
Financing Receivable Modifications [Line Items] |  |  |  |  |
Number of Contracts Modified in the Last three Months | Contract |  |  | 2 |  |
Pre-Modification Outstanding Recorded Investment |  |  | $ 981 |  |
Post-Modification Outstanding Recorded Investment |  |  | $ 981 |  |
Ag Real Estate [Member] |  |  |  |  |
Financing Receivable Modifications [Line Items] |  |  |  |  |
Number of Contracts Modified in the Last three Months | Contract | 2 |  | 2 |  |
Pre-Modification Outstanding Recorded Investment | $ 5,380 |  | $ 5,380 |  |
Post-Modification Outstanding Recorded Investment | $ 5,380 |  | $ 5,380 |  |
Commercial and Industrial [Member] |  |  |  |  |
Financing Receivable Modifications [Line Items] |  |  |  |  |
Number of Contracts Modified in the Last three Months | Contract |  | 4 |  | 4 |
Pre-Modification Outstanding Recorded Investment |  | $ 812 |  | $ 812 |
Post-Modification Outstanding Recorded Investment |  | $ 812 |  | $ 812 |
Agricultural [Member] |  |  |  |  |
Financing Receivable Modifications [Line Items] |  |  |  |  |
Number of Contracts Modified in the Last three Months | Contract | 1 |  | 1 |  |
Pre-Modification Outstanding Recorded Investment | $ 164 |  | $ 164 |  |
Post-Modification Outstanding Recorded Investment | $ 164 |  | $ 164 |  |

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