FAIR VALUE - Quantitative Information (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Corporate Bonds and Notes | Recurring | Discounted cash flow
Information related to Level 3 non-recurring fair value measurement [Abstract]
Assets, fair value disclosure		$ 250
Corporate Bonds and Notes | Recurring | Discounted cash flow | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit spread		1.73%
Corporate Bonds and Notes | Recurring | Discounted cash flow | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit spread		1.73%
Corporate Bonds and Notes | Recurring | Discounted cash flow | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit spread		1.73%
Impaired Loans: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 3,242	$ 2,850
Other real estate owned: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	179	344
Other real estate owned: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	179	344
Derivative Liabilities | Recurring | Historical trend
Information related to Level 3 non-recurring fair value measurement [Abstract]
Liabilities, fair value disclosure	$ 71	$ 68
Derivative Liabilities | Recurring | Historical trend | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.15%	4.92%
Derivative Liabilities | Recurring | Historical trend | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.15%	4.92%
Derivative Liabilities | Recurring | Historical trend | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Credit default rate	5.15%	4.92%
Commercial and Industrial | Impaired Loans: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 85
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	36.07%
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	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	36.07%
Commercial and Industrial | Impaired Loans: | Non-recurring | Income approach | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	5.00%
Commercial and Industrial | Impaired Loans: | Non-recurring | Income approach | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	5.00%
Commercial and Industrial | Impaired Loans: | Non-recurring | Income approach | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	5.00%
Commercial mortgages, other | Impaired Loans: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value		$ 2,631
Commercial mortgages, other | Impaired Loans: | Non-recurring | Sales comparison
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 707
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	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	44.52%
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	20.34%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Income approach
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value	$ 2,450
Commercial mortgages, other | Impaired Loans: | Non-recurring | Income approach | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Capitalization rate	9.00%	9.00%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Income approach | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Capitalization rate	10.00%	10.00%
Commercial mortgages, other | Impaired Loans: | Non-recurring | Income approach | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Capitalization rate	9.52%	9.52%
Home equity lines and loans | Impaired Loans: | Non-recurring
Information related to Level 3 non-recurring fair value measurement [Abstract]
Fair value		$ 219
Home equity lines and loans | Impaired Loans: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value		22.98%
Home equity lines and loans | Impaired Loans: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value		22.98%
Home equity lines and loans | Impaired Loans: | Non-recurring | Sales comparison | Weighted Average
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value		22.98%
Residential mortgages | Other real estate owned: | Non-recurring | Sales comparison | Minimum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	17.28%	20.80%
Residential mortgages | Other real estate owned: | Non-recurring | Sales comparison | Maximum
Information related to Level 3 non-recurring fair value measurement [Abstract]
Discount to appraised value	27.97%	48.17%
Residential mortgages | 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	20.73%	30.50%