LOANS AND ALLOWANCE FOR LOAN LOSSES (Activity in Allowance for Loan Losses by Portfolio Segment) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for unfunded commitments	$ 14,000	$ 16,000	$ 14,000	$ 16,000	$ 22,000
Activity in ALL:
Beginning balance	25,201,000	22,990,000	24,712,000	24,171,000	24,171,000
Loans charged off	(271,000)	(389,000)	(607,000)	(1,192,000)	(2,248,000)
Recoveries	58,000	77,000	133,000	199,000	1,944,000
Provision (credit)(1)	1,175,000	990,000	1,925,000	490,000	845,000
Ending balance	26,163,000	23,668,000	26,163,000	23,668,000	24,712,000
Ending Balance: Individually evaluated for impairment	1,183,000	834,000	1,183,000	834,000	824,000
Ending Balance: Collectively evaluated for impairment	24,980,000	22,834,000	24,980,000	22,834,000	23,888,000
Ending Balance: Individually evaluated for impairment	6,443,000	12,591,000	6,443,000	12,591,000	6,926,000
Ending Balance: Collectively evaluated for impairment	3,093,881,000	2,854,938,000	3,093,881,000	2,854,938,000	3,019,296,000
Total Loans Outstanding	3,100,324,000	2,867,529,000	3,100,324,000	2,867,529,000	3,026,222,000
Residential Real Estate
Activity in ALL:
Beginning balance	6,153,000	5,497,000	6,071,000	5,086,000	5,086,000
Loans charged off	(14,000)	(85,000)	(25,000)	(116,000)	(173,000)
Recoveries	2,000	15,000	4,000	15,000	90,000
Provision (credit)(1)	108,000	352,000	199,000	794,000	1,068,000
Ending balance	6,249,000	5,779,000	6,249,000	5,779,000	6,071,000
Ending Balance: Individually evaluated for impairment	524,000	585,000	524,000	585,000	586,000
Ending Balance: Collectively evaluated for impairment	5,725,000	5,194,000	5,725,000	5,194,000	5,485,000
Ending Balance: Individually evaluated for impairment	4,472,000	5,400,000	4,472,000	5,400,000	4,762,000
Ending Balance: Collectively evaluated for impairment	1,031,320,000	902,510,000	1,031,320,000	902,510,000	988,104,000
Total Loans Outstanding	1,035,792,000	907,910,000	1,035,792,000	907,910,000	992,866,000
Commercial Real Estate
Activity in ALL:
Beginning balance	11,838,000	10,286,000	11,654,000	11,863,000	11,863,000
Loans charged off	0	(86,000)	(65,000)	(512,000)	(512,000)
Recoveries	3,000	2,000	7,000	15,000	28,000
Provision (credit)(1)	311,000	108,000	556,000	(1,056,000)	275,000
Ending balance	12,152,000	10,310,000	12,152,000	10,310,000	11,654,000
Ending Balance: Individually evaluated for impairment	27,000	23,000	27,000	23,000	23,000
Ending Balance: Collectively evaluated for impairment	12,125,000	10,287,000	12,125,000	10,287,000	11,631,000
Ending Balance: Individually evaluated for impairment	409,000	5,093,000	409,000	5,093,000	930,000
Ending Balance: Collectively evaluated for impairment	1,260,230,000	1,184,959,000	1,260,230,000	1,184,959,000	1,268,603,000
Total Loans Outstanding	1,260,639,000	1,190,052,000	1,260,639,000	1,190,052,000	1,269,533,000
Commercial
Activity in ALL:
Beginning balance	3,616,000	4,126,000	3,620,000	4,171,000	4,171,000
Loans charged off	(217,000)	(127,000)	(453,000)	(298,000)	(736,000)
Recoveries	49,000	57,000	111,000	120,000	1,770,000
Provision (credit)(1)	659,000	247,000	829,000	310,000	(1,585,000)
Ending balance	4,107,000	4,303,000	4,107,000	4,303,000	3,620,000
Ending Balance: Individually evaluated for impairment	322,000	0	322,000	0	53,000
Ending Balance: Collectively evaluated for impairment	3,785,000	4,303,000	3,785,000	4,303,000	3,567,000
Ending Balance: Individually evaluated for impairment	675,000	1,611,000	675,000	1,611,000	786,000
Ending Balance: Collectively evaluated for impairment	428,001,000	384,782,000	428,001,000	384,782,000	380,994,000
Total Loans Outstanding	428,676,000	386,393,000	428,676,000	386,393,000	381,780,000
Home Equity
Activity in ALL:
Beginning balance	3,027,000	2,427,000	2,796,000	2,367,000	2,367,000
Loans charged off	(34,000)	(75,000)	(44,000)	(224,000)	(476,000)
Recoveries	0	1,000	0	44,000	44,000
Provision (credit)(1)	(1,000)	263,000	240,000	429,000	861,000
Ending balance	2,992,000	2,616,000	2,992,000	2,616,000	2,796,000
Ending Balance: Individually evaluated for impairment	310,000	226,000	310,000	226,000	162,000
Ending Balance: Collectively evaluated for impairment	2,682,000	2,390,000	2,682,000	2,390,000	2,634,000
Ending Balance: Individually evaluated for impairment	887,000	487,000	887,000	487,000	442,000
Ending Balance: Collectively evaluated for impairment	322,649,000	323,184,000	322,649,000	323,184,000	327,321,000
Total Loans Outstanding	323,536,000	323,671,000	323,536,000	323,671,000	327,763,000
Consumer
Activity in ALL:
Beginning balance	259,000	230,000	234,000	233,000	233,000
Loans charged off	(6,000)	(16,000)	(20,000)	(42,000)	(96,000)
Recoveries	4,000	2,000	11,000	5,000	11,000
Provision (credit)(1)	126,000	44,000	158,000	64,000	86,000
Ending balance	383,000	260,000	383,000	260,000	234,000
Ending Balance: Individually evaluated for impairment	0	0	0	0
Ending Balance: Collectively evaluated for impairment	383,000	260,000	383,000	260,000	234,000
Ending Balance: Individually evaluated for impairment	0	0	0	0	6,000
Ending Balance: Collectively evaluated for impairment	23,665,000	19,506,000	23,665,000	19,506,000	20,618,000
Total Loans Outstanding	23,665,000	19,506,000	23,665,000	19,506,000	20,624,000
HPFC Portfolio Segment
Activity in ALL:
Beginning balance	308,000	424,000	337,000	451,000	451,000
Loans charged off	0	0	0	0	(255,000)
Recoveries	0	0	0	0	1,000
Provision (credit)(1)	(28,000)	(24,000)	(57,000)	(51,000)	140,000
Ending balance	280,000	400,000	280,000	400,000	337,000
Ending Balance: Individually evaluated for impairment	0	0	0	0
Ending Balance: Collectively evaluated for impairment	280,000	400,000	280,000	400,000	337,000
Ending Balance: Individually evaluated for impairment	0	0	0	0
Ending Balance: Collectively evaluated for impairment	28,016,000	39,997,000	28,016,000	39,997,000	33,656,000
Total Loans Outstanding	$ 28,016,000	$ 39,997,000	$ 28,016,000	$ 39,997,000	$ 33,656,000