LOANS AND ALLOWANCE FOR LOAN LOSSES (Activity in Allowance for Loan Losses by Portfolio Segment) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for unfunded commitments	$ 22,000	$ 14,000	$ 22,000	$ 14,000	$ 11,000
Activity in ALL:
Beginning balance	24,394,000	23,717,000	23,116,000	21,166,000	21,166,000
Loans charged off	(908,000)	(1,841,000)	(1,931,000)	(3,268,000)	(3,805,000)
Recoveries	125,000	127,000	442,000	381,000	486,000
Provision (credit)(1)	802,000	1,287,000	2,786,000	5,011,000	5,269,000
Ending balance	24,413,000	23,290,000	24,413,000	23,290,000	23,116,000
Ending Balance: Individually evaluated for impairment	1,934,000	1,957,000	1,934,000	1,957,000	2,007,000
Ending Balance: Collectively evaluated for impairment	22,479,000	21,333,000	22,479,000	21,333,000	21,109,000
Ending Balance: Individually evaluated for impairment	13,430,000	20,682,000	13,430,000	20,682,000	20,254,000
Ending Balance: Collectively evaluated for impairment	2,734,860,000	2,571,327,000	2,734,860,000	2,571,327,000	2,574,310,000
Total Loans Outstanding	2,748,290,000	2,592,009,000	2,748,290,000	2,592,009,000	2,594,564,000
Residential Real Estate
Activity in ALL:
Beginning balance	4,481,000	4,431,000	4,160,000	4,545,000	4,545,000
Loans charged off	(238,000)	0	(433,000)	(229,000)	(356,000)
Recoveries	26,000	1,000	30,000	72,000	95,000
Provision (credit)(1)	273,000	163,000	785,000	207,000	(124,000)
Ending balance	4,542,000	4,595,000	4,542,000	4,595,000	4,160,000
Ending Balance: Individually evaluated for impairment	464,000	511,000	464,000	511,000	483,000
Ending Balance: Collectively evaluated for impairment	4,078,000	4,084,000	4,078,000	4,084,000	3,677,000
Ending Balance: Individually evaluated for impairment	4,792,000	4,551,000	4,792,000	4,551,000	4,348,000
Ending Balance: Collectively evaluated for impairment	848,059,000	792,485,000	848,059,000	792,485,000	798,146,000
Total Loans Outstanding	852,851,000	797,036,000	852,851,000	797,036,000	802,494,000
Commercial Real Estate
Activity in ALL:
Beginning balance	12,848,000	11,559,000	12,154,000	10,432,000	10,432,000
Loans charged off	(69,000)	(32,000)	(81,000)	(273,000)	(315,000)
Recoveries	25,000	7,000	138,000	50,000	50,000
Provision (credit)(1)	(8,000)	1,046,000	585,000	2,371,000	1,987,000
Ending balance	12,796,000	12,580,000	12,796,000	12,580,000	12,154,000
Ending Balance: Individually evaluated for impairment	1,470,000	1,284,000	1,470,000	1,284,000	1,373,000
Ending Balance: Collectively evaluated for impairment	11,326,000	11,296,000	11,326,000	11,296,000	10,781,000
Ending Balance: Individually evaluated for impairment	6,373,000	13,286,000	6,373,000	13,286,000	13,317,000
Ending Balance: Collectively evaluated for impairment	1,125,510,000	1,041,021,000	1,125,510,000	1,041,021,000	1,037,463,000
Total Loans Outstanding	1,131,883,000	1,054,307,000	1,131,883,000	1,054,307,000	1,050,780,000
Commercial
Activity in ALL:
Beginning balance	4,275,000	4,558,000	3,755,000	3,241,000	3,241,000
Loans charged off	(369,000)	(1,541,000)	(650,000)	(1,970,000)	(2,218,000)
Recoveries	59,000	118,000	254,000	252,000	332,000
Provision (credit)(1)	256,000	148,000	862,000	1,760,000	2,400,000
Ending balance	4,221,000	3,283,000	4,221,000	3,283,000	3,755,000
Ending Balance: Individually evaluated for impairment	0	0	0	0
Ending Balance: Collectively evaluated for impairment	4,221,000	3,283,000	4,221,000	3,283,000	3,755,000
Ending Balance: Individually evaluated for impairment	1,842,000	2,243,000	1,842,000	2,243,000	2,028,000
Ending Balance: Collectively evaluated for impairment	367,313,000	322,179,000	367,313,000	322,179,000	331,611,000
Total Loans Outstanding	369,155,000	324,422,000	369,155,000	324,422,000	333,639,000
Home Equity
Activity in ALL:
Beginning balance	2,094,000	2,946,000	2,194,000	2,731,000	2,731,000
Loans charged off	(11,000)	(44,000)	(403,000)	(229,000)	(308,000)
Recoveries	1,000	0	2,000	2,000	2,000
Provision (credit)(1)	93,000	(335,000)	384,000	63,000	(231,000)
Ending balance	2,177,000	2,567,000	2,177,000	2,567,000	2,194,000
Ending Balance: Individually evaluated for impairment	0	88,000	0	88,000	86,000
Ending Balance: Collectively evaluated for impairment	2,177,000	2,479,000	2,177,000	2,479,000	2,108,000
Ending Balance: Individually evaluated for impairment	423,000	489,000	423,000	489,000	457,000
Ending Balance: Collectively evaluated for impairment	327,905,000	332,606,000	327,905,000	332,606,000	329,450,000
Total Loans Outstanding	328,328,000	333,095,000	328,328,000	333,095,000	329,907,000
Consumer
Activity in ALL:
Beginning balance	182,000	193,000	181,000	193,000	193,000
Loans charged off	(28,000)	(19,000)	(90,000)	(60,000)	(101,000)
Recoveries	9,000	1,000	13,000	5,000	7,000
Provision (credit)(1)	32,000	(13,000)	91,000	24,000	82,000
Ending balance	195,000	162,000	195,000	162,000	181,000
Ending Balance: Individually evaluated for impairment	0	0	0	0
Ending Balance: Collectively evaluated for impairment	195,000	162,000	195,000	162,000	181,000
Ending Balance: Individually evaluated for impairment	0	7,000	0	7,000	7,000
Ending Balance: Collectively evaluated for impairment	18,123,000	17,409,000	18,123,000	17,409,000	17,325,000
Total Loans Outstanding	18,123,000	17,416,000	18,123,000	17,416,000	17,332,000
HPFC Portfolio Segment
Activity in ALL:
Beginning balance	514,000	30,000	672,000	24,000	24,000
Loans charged off	(193,000)	(205,000)	(274,000)	(507,000)	(507,000)
Recoveries	5,000	0	5,000	0
Provision (credit)(1)	156,000	278,000	79,000	586,000	1,155,000
Ending balance	482,000	103,000	482,000	103,000	672,000
Ending Balance: Individually evaluated for impairment	0	74,000	0	74,000	65,000
Ending Balance: Collectively evaluated for impairment	482,000	29,000	482,000	29,000	607,000
Ending Balance: Individually evaluated for impairment	0	106,000	0	106,000	97,000
Ending Balance: Collectively evaluated for impairment	47,950,000	65,627,000	47,950,000	65,627,000	60,315,000
Total Loans Outstanding	$ 47,950,000	$ 65,733,000	$ 47,950,000	$ 65,733,000	$ 60,412,000