LOANS AND ALLOWANCE FOR LOAN LOSSES (Summary of Impaired Loan Balances and Associated Allowance by Portfolio Segment) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	$ 4,244	$ 8,851	$ 4,244	$ 8,851	$ 9,280
Unpaid Principal Balance - with an allowance recorded	4,244	8,851	4,244	8,851	9,280
Related Allowance	756	1,934	756	1,934	2,009
Average Recorded Investment - with an allowance recorded	4,282	9,866	5,088	13,373	12,257
Interest Income Recognized - with an allowance recorded	33	52	113	118	153
Recorded Investment - without allowance recorded	7,868	4,579	7,868	4,579	4,310
Unpaid Principal Balance - without allowance recorded	9,682	6,478	9,682	6,478	6,216
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded	8,069	4,552	6,098	4,832	4,709
Interest Income Recognized - without allowance recorded	15	21	33	51	62
Impaired Financing Receivable, Recorded Investment	12,112	13,430	12,112	13,430	13,590
Impaired financing receivable, unpaid principal balance	13,926	15,329	13,926	15,329	15,496
Impaired Financing Receivable, Average Recorded Investment	12,351	14,418	11,186	18,205	16,966
Impaired Financing Receivable, Interest Income, Accrual Method	48	73	146	169	215
Residential Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	3,577	3,262	3,577	3,262	3,858
Unpaid Principal Balance - with an allowance recorded	3,577	3,262	3,577	3,262	3,858
Related Allowance	619	464	619	464	568
Average Recorded Investment - with an allowance recorded	3,541	3,194	2,428	3,084	3,177
Interest Income Recognized - with an allowance recorded	27	48	96	103	131
Recorded Investment - without allowance recorded	1,607	1,530	1,607	1,530	1,313
Unpaid Principal Balance - without allowance recorded	1,807	1,949	1,807	1,949	1,673
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded	1,750	1,427	1,582	1,349	1,345
Interest Income Recognized - without allowance recorded	13	15	27	15	15
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	349	5,589	349	5,589	5,422
Unpaid Principal Balance - with an allowance recorded	349	5,589	349	5,589	5,422
Related Allowance	23	1,470	23	1,470	1,441
Average Recorded Investment - with an allowance recorded	350	6,590	2,428	10,048	8,900
Interest Income Recognized - with an allowance recorded	6	4	17	15	22
Recorded Investment - without allowance recorded	4,658	784	4,658	784	777
Unpaid Principal Balance - without allowance recorded	4,944	1,032	4,944	1,032	1,084
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded	4,700	794	2,637	1,250	1,132
Interest Income Recognized - without allowance recorded		15		22	29
Commercial
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	0	0	0	0	0
Unpaid Principal Balance - with an allowance recorded	0	0	0	0	0
Related Allowance	0	0	0	0	0
Average Recorded Investment - with an allowance recorded		82		41	31
Recorded Investment - without allowance recorded	1,548	1,842	1,548	1,842	1,791
Unpaid Principal Balance - without allowance recorded	2,725	3,015	2,725	3,015	2,964
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded	1,580	1,891	1,666	1,959	1,920
Interest Income Recognized - without allowance recorded	2	(6)	6	8	10
Home Equity
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	318	0	318	0	0
Unpaid Principal Balance - with an allowance recorded	318	0	318	0	0
Related Allowance	114	0	114	0	0
Average Recorded Investment - with an allowance recorded	391		232	167	125
Recorded Investment - without allowance recorded	55	423	55	423	429
Unpaid Principal Balance - without allowance recorded	206	482	206	482	495
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded	39	440	213	271	310
Interest Income Recognized - without allowance recorded		1		6	8
Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	0	0	0	0	0
Unpaid Principal Balance - with an allowance recorded	0	0	0	0	0
Related Allowance	0	0	0	0	0
Average Recorded Investment - with an allowance recorded					0
Recorded Investment - without allowance recorded	0	0	0	0	0
Unpaid Principal Balance - without allowance recorded	0	0	0	0	0
Impaired Financing Receivable With No Related Allowance Related Allowance	0	0	0	0
Average Recorded Investment - without allowance recorded				3	2
Interest Income Recognized - without allowance recorded		(4)
HPFC Portfolio Segment
Financing Receivable, Impaired [Line Items]
Recorded Investment - with an allowance recorded	0	0	0	0	0
Unpaid Principal Balance - with an allowance recorded	0	0	0	0	0
Related Allowance	0	0	0	0	0
Average Recorded Investment - with an allowance recorded				33	24
Recorded Investment - without allowance recorded	0	0	0	0	0
Unpaid Principal Balance - without allowance recorded	0	0	0	0	0
Impaired Financing Receivable With No Related Allowance Related Allowance	$ 0	$ 0	$ 0	$ 0
Average Recorded Investment - without allowance recorded					$ 0

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