LOANS AND THE ALLOWANCE FOR LOAN LOSSES - Aging analysis of recorded investments by class (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 24,928	$ 7,986
Total current	831,229	804,711
Total Recorded Investment	856,157	812,697
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	5,956	3,664
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	584	99
90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	18,388	4,223
Cash, Securities and Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	11,481	149
Total current	121,439	131,607
Total Recorded Investment	132,920	131,756
Cash, Securities and Other | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	188	50
Cash, Securities and Other | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	16	99
Cash, Securities and Other | 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	11,277
Construction and Development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	4,473
Total current	32,950	24,914
Total Recorded Investment	37,423	24,914
Construction and Development | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	4,473
1-4 Family Residential, Non-Owner Occupied CRE and Owner Occupied CRE
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	5,300
1-4 Family Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,917	3,638
Total current	325,757	278,376
Total Recorded Investment	$ 327,674	$ 282,014
Number of loans, 90 days delinquent and accruing interest | loan	1	1
90 days past due and accruing interest	$ 1,200	$ 1,200
1-4 Family Residential | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	700	1,250
1-4 Family Residential | 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,217	2,388
Non-Owner Occupied CRE
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	3,356	750
Total current	162,314	176,237
Total Recorded Investment	165,670	176,987
Non-Owner Occupied CRE | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	595	750
Non-Owner Occupied CRE | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	568
Non-Owner Occupied CRE | 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	2,193
Owner Occupied CRE
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,866
Total current	92,832	92,742
Total Recorded Investment	94,698	92,742
Owner Occupied CRE | 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,866
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,835	3,449
Total current	95,937	100,835
Total Recorded Investment	97,772	104,284
Commercial and Industrial | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1,614
Commercial and Industrial | 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 1,835	$ 1,835