FAIR VALUE - Quantitative Information (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Impaired Loans: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 350	$ 507
Other real estate owned: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	1,832	1,940
Other real estate owned: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	283	382
Derivative Liabilities | Recurring | Historical trend
Information related to Level 3 non-recurring fair value measurement [Abstract]
Liabilities, fair value disclosure	$ 50	$ 75
Derivative Liabilities | Recurring | Historical trend | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.52%	5.67%
Derivative Liabilities | Recurring | Historical trend | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.52%	5.67%
Derivative Liabilities | Recurring | Historical trend | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.52%	5.67%
Commercial and Industrial | Impaired Loans: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 12	$ 96
Commercial and Industrial | Impaired Loans: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	0.00%	0.00%
Commercial and Industrial | Impaired Loans: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	0.00%	36.07%
Commercial and Industrial | Impaired Loans: | Non-recurring | Sales comparison | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	0.00%	33.02%
Commercial and Industrial | Other real estate owned: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value		$ 1,483
Commercial and Industrial | Other real estate owned: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	10.00%	10.00%
Commercial and Industrial | Other real estate owned: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	22.95%	22.95%
Commercial and Industrial | Other real estate owned: | Non-recurring | Sales comparison | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	19.75%	19.75%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 338	$ 411
Commercial mortgages, other | Impaired Loans: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	21.98%	10.00%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	69.81%	89.98%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Sales comparison | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	55.51%	51.35%
Commercial mortgages, other | Other real estate owned: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 1,474
Home equity lines and loans | Other real estate owned: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 75	$ 75
Residential mortgages | Other real estate owned: | Non-recurring | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	17.28%	17.28%
Residential mortgages | Other real estate owned: | Non-recurring | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	39.78%	27.97%
Residential mortgages | Other real estate owned: | Non-recurring | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	20.39%	20.77%
Home equity lines and loans | Other real estate owned: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	20.80%	20.80%
Home equity lines and loans | Other real estate owned: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	20.80%	20.80%
Home equity lines and loans | Other real estate owned: | Non-recurring | Sales comparison | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	20.80%	20.80%