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LOANS AND ALLOWANCE FOR LOAN LOSSES - Impaired Loans (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Unpaid Principal Balance [Abstract] |  |  |
Unpaid principal balance, total | $ 13,842 |  | $ 14,094
Recorded Investment [Abstract] |  |  |
Recorded investment, total | 13,640 |  | 13,926
Allowance for loan losses allocated | 5,681 |  | 5,937
Average Recorded Investment [Abstract] |  |  |
Average recorded investment, total | 13,784 | $ 12,684 |
Interest Income, Accrual Method [Abstract] |  |  |
Interest income, accrual method, total | 21 | 75 |
Commercial Mortgages | Construction |  |  |
Unpaid Principal Balance [Abstract] |  |  |
With no related allowance, Unpaid Principal Balance | 351 |  | 364
Recorded Investment [Abstract] |  |  |
With no related allowance, Recorded Investment | 352 |  | 365
Average Recorded Investment [Abstract] |  |  |
With no related allowance, Average Recorded Investment | 359 | 919 |
Interest Income, Accrual Method [Abstract] |  |  |
With no related allowance, Interest Income, Accrual Method | 3 | 3 |
Commercial Mortgages | Commercial mortgages, other |  |  |
Unpaid Principal Balance [Abstract] |  |  |
With no related allowance, Unpaid Principal Balance | 4,210 |  | 4,135
With related allowance, Unpaid Principal Balance | 2,984 |  | 2,989
Recorded Investment [Abstract] |  |  |
With no related allowance, Recorded Investment | 4,212 |  | 4,138
With related allowance, Recorded Investment | 2,795 |  | 2,799
Allowance for loan losses allocated | 771 |  | 802
Average Recorded Investment [Abstract] |  |  |
With no related allowance, Average Recorded Investment | 4,175 | 7,000 |
With related allowance, Average Recorded Investment | 2,797 | 3,257 |
Interest Income, Accrual Method [Abstract] |  |  |
With no related allowance, Interest Income, Accrual Method | 5 | 59 |
With related allowance, Interest Income, Accrual Method | 1 | 1 |
Residential mortgages |  |  |
Unpaid Principal Balance [Abstract] |  |  |
With no related allowance, Unpaid Principal Balance | 447 |  | 450
Recorded Investment [Abstract] |  |  |
With no related allowance, Recorded Investment | 425 |  | 427
Average Recorded Investment [Abstract] |  |  |
With no related allowance, Average Recorded Investment | 426 | 393 |
Interest Income, Accrual Method [Abstract] |  |  |
With no related allowance, Interest Income, Accrual Method | 2 | 2 |
Consumer loans: | Home equity lines and loans |  |  |
Unpaid Principal Balance [Abstract] |  |  |
With no related allowance, Unpaid Principal Balance | 61 |  | 64
Recorded Investment [Abstract] |  |  |
With no related allowance, Recorded Investment | 61 |  | 64
Average Recorded Investment [Abstract] |  |  |
With no related allowance, Average Recorded Investment | 63 | 84 |
With related allowance, Average Recorded Investment | 0 | 360 |
Interest Income, Accrual Method [Abstract] |  |  |
With no related allowance, Interest Income, Accrual Method | 1 | 1 |
With related allowance, Interest Income, Accrual Method | 0 | 0 |
Commercial and industrial | Commercial and agricultural: |  |  |
Unpaid Principal Balance [Abstract] |  |  |
With no related allowance, Unpaid Principal Balance | 770 |  | 861
With related allowance, Unpaid Principal Balance | 5,019 |  | 5,231
Recorded Investment [Abstract] |  |  |
With no related allowance, Recorded Investment | 773 |  | 867
With related allowance, Recorded Investment | 5,022 |  | 5,266
Allowance for loan losses allocated | 4,910 |  | $ 5,135
Average Recorded Investment [Abstract] |  |  |
With no related allowance, Average Recorded Investment | 820 | 671 |
With related allowance, Average Recorded Investment | 5,144 | 0 |
Interest Income, Accrual Method [Abstract] |  |  |
With no related allowance, Interest Income, Accrual Method | 9 | 9 |
With related allowance, Interest Income, Accrual Method | $ 0 | $ 0 |

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