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Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2020 | Sep. 30, 2020 | Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Increase in available commitments | $ 36,900 |  |  |
Commercial lines of credit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 297,898 | $ 297,898 |  | $ 287,533
Revolving home equity lines |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 191,969 | 191,969 |  | 189,035
Undisbursed construction loans |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 101,307 | 101,307 |  | 41,033
Personal and other lines of credit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 10,611 | 10,611 |  | 9,567
Standby letters of credit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 2,657 | 2,657 |  | 1,964
Total unfunded loan commitments and standby letters of credit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Loan commitments and standby letters of credit, off-balance sheet | 604,442 | $ 604,442 |  | 529,132
Percentage of commitments expiring in 2021 |  | 35.00% |  |
Percentage of commitments expiring between 2022 and 2028 |  | 54.00% |  |
Percentage of commitments expiring 2028 and thereafter |  | 11.00% |  |
Allowance for off-balance sheet commitments |  |  | $ 610 | $ 1,100
Total unfunded loan commitments and standby letters of credit | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Allowance for off-balance sheet commitments | 1,100 | $ 1,100 |  |
Total unfunded loan commitments and standby letters of credit | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Allowance for off-balance sheet commitments | $ 550 | $ 550 |  |

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