LOANS AND ALLOWANCE FOR LOAN LOSSES (Loan Aging Analysis by Portfolio Segment) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) loan	Sep. 30, 2017 USD ($) loan	Sep. 30, 2018 USD ($) loan	Sep. 30, 2017 USD ($) loan	Dec. 31, 2017 USD ($)
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of TDRs | loan	2	3	3	5
Total Past Due	$ 20,677,000		$ 20,677,000		$ 22,945,000
Current	2,888,166,000		2,888,166,000		2,759,494,000
Total Loans Outstanding	2,908,843,000	$ 2,748,290,000	2,908,843,000	$ 2,748,290,000	2,782,439,000
Loans 90 Days Past Due and Accruing	14,000		14,000		0
Non-Accrual Loans	14,877,000		14,877,000		15,314,000
Financing Receivable, Modifications, Pre-Modification Recorded Investment	234,000	429,000	397,000	895,000
Financing Receivable, Modifications, Post-Modification Recorded Investment	234,000	448,000	420,000	914,000
Allowance Related to Troubled Debt Restructurings assigned during period	57,000	29,000	96,000	44,000
Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,779,000		7,779,000		9,477,000
Current	933,709,000		933,709,000		848,892,000
Total Loans Outstanding	941,488,000	852,851,000	941,488,000	852,851,000	858,369,000
Loans 90 Days Past Due and Accruing	0		0		0
Non-Accrual Loans	4,720,000		4,720,000		4,979,000
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,066,000		6,066,000		6,700,000
Current	1,209,913,000		1,209,913,000		1,157,323,000
Total Loans Outstanding	1,215,979,000	1,131,883,000	1,215,979,000	1,131,883,000	1,164,023,000
Loans 90 Days Past Due and Accruing	0		0		0
Non-Accrual Loans	5,517,000		5,517,000		5,642,000
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,763,000		2,763,000		2,223,000
Current	366,074,000		366,074,000		371,177,000
Total Loans Outstanding	368,837,000	369,155,000	368,837,000	369,155,000	373,400,000
Loans 90 Days Past Due and Accruing	0		0		0
Non-Accrual Loans	2,402,000		2,402,000		2,000,000
Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,304,000		2,304,000		2,548,000
Current	323,148,000		323,148,000		320,830,000
Total Loans Outstanding	325,452,000	328,328,000	325,452,000	328,328,000	323,378,000
Loans 90 Days Past Due and Accruing	0		0		0
Non-Accrual Loans	1,614,000		1,614,000		1,650,000
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	97,000		97,000		67,000
Current	20,161,000		20,161,000		18,082,000
Total Loans Outstanding	20,258,000	18,123,000	20,258,000	18,123,000	18,149,000
Loans 90 Days Past Due and Accruing	14,000		14,000		0
Non-Accrual Loans	33,000		33,000		0
HPFC Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,668,000		1,668,000		1,930,000
Current	35,161,000		35,161,000		43,190,000
Total Loans Outstanding	36,829,000	$ 47,950,000	36,829,000	$ 47,950,000	45,120,000
Loans 90 Days Past Due and Accruing	0		0		0
Non-Accrual Loans	591,000		591,000		1,043,000
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,223,000		5,223,000		6,291,000
30-59 Days Past Due | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,342,000		3,342,000		3,871,000
30-59 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	607,000		607,000		849,000
30-59 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	79,000		79,000		329,000
30-59 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	542,000		542,000		1,046,000
30-59 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	36,000		36,000		57,000
30-59 Days Past Due | HPFC Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	617,000		617,000		139,000
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,193,000		2,193,000		3,822,000
60-89 Days Past Due | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	636,000		636,000		1,585,000
60-89 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	104,000		104,000		323,000
60-89 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	644,000		644,000		359,000
60-89 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	335,000		335,000		173,000
60-89 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,000		14,000		10,000
60-89 Days Past Due | HPFC Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	460,000		460,000		1,372,000
Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13,261,000		13,261,000		12,832,000
Greater than 90 Days | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,801,000		3,801,000		4,021,000
Greater than 90 Days | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,355,000		5,355,000		5,528,000
Greater than 90 Days | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,040,000		2,040,000		1,535,000
Greater than 90 Days | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,427,000		1,427,000		1,329,000
Greater than 90 Days | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	47,000		47,000		0
Greater than 90 Days | HPFC Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 591,000		$ 591,000		$ 419,000