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Loans (Impaired Loans) - Additional Information (Detail) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 USD ($) Contract Loan | Mar. 31, 2019 USD ($) Loan | Dec. 31, 2019 USD ($) Loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Additional funds available to be advanced in connection with impaired loans | $ 45,000 |  |
Impaired loans classified as troubled debt restructured | $ 1,900,000 | $ 173,000 | $ 1,000,000
Number of contracts modified | Loan | 2 |  | 0
TDR loans, subsequently defaulted during the period | 0 | 0 |
TDR impaired loans paid off | Loan | 1 | 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 | $ 185,000 |  | $ 214,000
Consumer Real Estate [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Foreclosed residential real estate property | 50,000 | $ 0 |
Residential real estate properties foreclosure proceedings | $ 292,000 | $ 639,000 |
Principal Forgiveness [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Number of contracts modified | Contract | 0 |  |
Payment Changes from Monthly Payment to Principal and Interest at Maturity [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Number of contracts modified | Contract | 2 |  |
Loan maturity date | Jun. 19, 2020 |  |

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