LOANS AND ALLOWANCE FOR LOAN LOSSES (Credit Risk Exposure Indicators by Portfolio Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 2,748,290	$ 2,594,564	$ 2,592,009
Pass (Grades 1-6)
Financing Receivable, Recorded Investment [Line Items]
Loans	2,335,658	2,173,031
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	344,825	345,615
Special Mention (Grade 7)
Financing Receivable, Recorded Investment [Line Items]
Loans	19,575	13,966
Substandard (Grade 8)
Financing Receivable, Recorded Investment [Line Items]
Loans	45,209	58,872
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,397	1,456
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans	1,626	1,624
Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans	852,851	802,494	797,036
Residential Real Estate | Pass (Grades 1-6)
Financing Receivable, Recorded Investment [Line Items]
Loans	841,539	789,554
Residential Real Estate | Special Mention (Grade 7)
Financing Receivable, Recorded Investment [Line Items]
Loans	933	2,387
Residential Real Estate | Substandard (Grade 8)
Financing Receivable, Recorded Investment [Line Items]
Loans	10,379	10,553
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans	1,131,883	1,050,780	1,054,307
Commercial Real Estate | Pass (Grades 1-6)
Financing Receivable, Recorded Investment [Line Items]
Loans	1,086,856	1,003,386
Commercial Real Estate | Special Mention (Grade 7)
Financing Receivable, Recorded Investment [Line Items]
Loans	16,663	5,724
Commercial Real Estate | Substandard (Grade 8)
Financing Receivable, Recorded Investment [Line Items]
Loans	28,364	41,670
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans	369,155	333,639	324,422
Commercial | Pass (Grades 1-6)
Financing Receivable, Recorded Investment [Line Items]
Loans	361,343	321,148
Commercial | Special Mention (Grade 7)
Financing Receivable, Recorded Investment [Line Items]
Loans	1,770	5,598
Commercial | Substandard (Grade 8)
Financing Receivable, Recorded Investment [Line Items]
Loans	4,645	5,437
Commercial | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,397	1,456
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Loans	328,328	329,907	333,095
Home Equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	326,702	328,287
Home Equity | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans	1,626	1,620
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	18,123	17,332	17,416
Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	18,123	17,328
Consumer | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans		4
HPFC Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans	47,950	60,412	$ 65,733
HPFC Portfolio Segment | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	45,920	58,943
HPFC Portfolio Segment | Substandard (Grade 8)
Financing Receivable, Recorded Investment [Line Items]
Loans	209	257
HPFC Portfolio Segment | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 1,821	$ 1,212