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Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
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 | $ 224,370 | $ 216,774
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 | 177,678 | 148,143
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 | 35,322 | 44,798
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 | 11,758 | 10,635
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 | 4,074 | 1,939
Total 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 | $ 453,202 | 422,289
Percentage of commitments expiring in 2018 | 44.00% |
Percentage of commitments expiring between 2019 and 2025 | 41.00% |
Percentage of commitments expiring 2026 and thereafter | 15.00% |
Total commitments and standby letters of credit | Interest Payable and Other Liabilities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Allowance for off-balance sheet commitments | $ 958 | $ 899

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