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Loans (Impaired Loans) - Additional Information (Detail) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) Contract | Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Additional funds available to be advanced in connection with impaired loans | $ 4 |
Impaired loans classified as troubled debt restructured | $ 956 | $ 178
TDR loans, subsequently defaulted during the period | 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 | 120 days |
Delinquent period for charging down commercial and agricultural credits | 120 days |
Foreclosed residential real estate property | $ 214 | $ 600
Consumer Real Estate [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Number of contracts modified | Contract | 1 |
Foreclosed residential real estate property | $ 50 | 61
Residential real estate properties foreclosure proceedings | $ 383 | $ 278
Principal Forgiveness [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Number of contracts modified | Contract | 0 |
Payment Changes to Interest Only for Extended Maturity [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Number of contracts modified | Contract | 4 |
Lowering of Payment to Match Extended Maturity [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Number of contracts modified | Contract | 1 |

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