LOANS - Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	$ 299	$ 1,834
Nonaccrual Including 90 Days or More Past Due	1,944	6,955
Total Past Due and Nonaccrual	8,044	12,403
Current	3,183,364	3,085,850
Total Loans	3,191,408	3,098,253
30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	5,157	2,854
60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	644	760
Commercial Real Estate | Mortgage loans
Past Due and Nonaccrual Loans
Total Loans	1,348,569	1,293,906
Commercial Real Estate | Mortgage loans | Owner occupied
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	175
Nonaccrual Including 90 Days or More Past Due	355	2,205
Total Past Due and Nonaccrual	548	2,664
Current	497,779	469,985
Total Loans	498,327	472,649
Commercial Real Estate | Mortgage loans | Owner occupied | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	193	284
Commercial Real Estate | Mortgage loans | Owner occupied | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Commercial Real Estate | Mortgage loans | Non-owner occupied
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	1,163
Nonaccrual Including 90 Days or More Past Due	0	0
Total Past Due and Nonaccrual	223	1,163
Current	850,019	820,094
Total Loans	850,242	821,257
Commercial Real Estate | Mortgage loans | Non-owner occupied | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	223	0
Commercial Real Estate | Mortgage loans | Non-owner occupied | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Multi-family | Mortgage loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	0	0
Total Past Due and Nonaccrual	0	0
Current	579,827	595,280
Total Loans	579,827	595,280
Multi-family | Mortgage loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Multi-family | Mortgage loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Residential real estate | Mortgage loans
Past Due and Nonaccrual Loans
Total Loans	516,995	464,264
Residential real estate | Mortgage loans | Residential Real Estate Mortgage Loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	299	0
Nonaccrual Including 90 Days or More Past Due	39	401
Total Past Due and Nonaccrual	2,556	2,873
Current	445,213	395,300
Total Loans	447,769	398,173
Residential real estate | Mortgage loans | Residential Real Estate Mortgage Loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	2,014	2,074
Residential real estate | Mortgage loans | Residential Real Estate Mortgage Loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	204	398
Residential real estate | Mortgage loans | Home equity
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	271
Nonaccrual Including 90 Days or More Past Due	628	161
Total Past Due and Nonaccrual	1,327	761
Current	67,899	65,330
Total Loans	69,226	66,091
Residential real estate | Mortgage loans | Home equity | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	699	329
Residential real estate | Mortgage loans | Home equity | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Commercial and industrial
Past Due and Nonaccrual Loans
Total Loans	608,723	616,003
Commercial and industrial | Secured
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	225
Nonaccrual Including 90 Days or More Past Due	227	570
Total Past Due and Nonaccrual	1,255	949
Current	117,125	111,364
Total Loans	118,380	112,313
Commercial and industrial | Secured | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	887	113
Commercial and industrial | Secured | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	141	41
Commercial and industrial | Unsecured
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	506	3,618
Total Past Due and Nonaccrual	1,741	3,671
Current	488,602	500,019
Total Loans	490,343	503,690
Commercial and industrial | Unsecured | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	1,129	18
Commercial and industrial | Unsecured | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	106	35
Real estate construction and land loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	152	0
Total Past Due and Nonaccrual	152	281
Current	117,985	107,478
Total Loans	118,137	107,759
Real estate construction and land loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	0
Real estate construction and land loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	0	281
Installment/consumer loans
Past Due and Nonaccrual Loans
>90 Days Past Due and Accruing	0	0
Nonaccrual Including 90 Days or More Past Due	37	0
Total Past Due and Nonaccrual	242	41
Current	18,915	21,000
Total Loans	19,157	21,041
Installment/consumer loans | 30-59 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	12	36
Installment/consumer loans | 60-89 Days Past Due
Past Due and Nonaccrual Loans
Total Past Due and Nonaccrual	$ 193	$ 5