LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY - Summary of loan composition (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 2,166,181	$ 2,087,925
% of Total	100.00%	100.00%
Less ALLL	$ 13,153	$ 12,653	$ 11,820	$ 10,307
Loans, net	$ 2,153,028	$ 2,075,272
ALLL to loans	0.61%	0.61%
Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 1,485,165	$ 1,243,702
% of Total	100.00%	100.00%
Less ALLL	$ 11,448	$ 10,542	9,449
Loans, net	$ 1,473,717	$ 1,233,160
ALLL to loans	0.77%	0.85%
Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 681,016	$ 844,223
% of Total	100.00%	100.00%
Less ALLL	$ 1,705	$ 2,111	2,371
Loans, net	$ 679,311	$ 842,112
ALLL to loans	0.25%	0.25%
Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 441,353	$ 430,043
Owner-occupied commercial real estate (“CRE”) | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount		192,495
Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 26,493	$ 22,815
% of Total	1.00%	1.00%
Less ALLL	$ 304	$ 225	152
Loans, net	26,189	22,590
Retail & other | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 23,809	$ 18,254
% of Total	2.00%	2.00%
Less ALLL	$ 281	$ 200	132
Loans, net	23,528	18,054
Retail & other | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 2,684	$ 4,561
% of Total	1.00%	1.00%
Less ALLL	$ 23	$ 25	20
Loans, net	2,661	4,536
Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 684,920	$ 637,337
% of Total	32.00%	31.00%
Less ALLL	$ 5,271	$ 4,934	3,919
Loans, net	679,649	632,403
Commercial Portfolio Segment | Commercial & industrial | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 568,100	$ 488,600
% of Total	38.00%	39.00%
Less ALLL	$ 4,683	$ 4,192	3,150
Loans, net	563,417	484,408
Commercial Portfolio Segment | Commercial & industrial | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 116,820	$ 148,737
% of Total	17.00%	17.00%
Less ALLL	$ 588	$ 742	769
Loans, net	116,232	147,995
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 441,353	$ 430,043
% of Total	20.00%	21.00%
Less ALLL	$ 2,847	$ 2,607	2,867
Loans, net	438,506	427,436
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 283,531	$ 237,548
% of Total	19.00%	19.00%
Less ALLL	$ 2,439	$ 2,115	2,263
Loans, net	281,092	235,433
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 157,822	$ 192,495
% of Total	23.00%	23.00%
Less ALLL	$ 408	$ 492	604
Loans, net	157,414	192,003
Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 35,625	$ 35,455
% of Total	2.00%	2.00%
Less ALLL	$ 121	$ 129	150
Loans, net	35,504	35,326
Commercial Portfolio Segment | Agricultural (“AG”) production | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 11,113	$ 11,102
% of Total	1.00%	1.00%
Less ALLL	$ 110	$ 112	122
Loans, net	11,003	10,990
Commercial Portfolio Segment | Agricultural (“AG”) production | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 24,512	$ 24,353
% of Total	4.00%	3.00%
Less ALLL	$ 11	$ 17	28
Loans, net	24,501	24,336
Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 53,444	$ 51,778
% of Total	2.00%	2.00%
Less ALLL	$ 301	$ 296	285
Loans, net	53,143	51,482
Commercial Real Estate Portfolio Segment | AG real estate | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 31,374	$ 27,831
% of Total	2.00%	2.00%
Less ALLL	$ 255	$ 235	222
Loans, net	31,119	27,596
Commercial Real Estate Portfolio Segment | AG real estate | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 22,070	$ 23,947
% of Total	3.00%	3.00%
Less ALLL	$ 46	$ 61	63
Loans, net	22,024	23,886
Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 343,652	$ 314,463
% of Total	16.00%	15.00%
Less ALLL	$ 1,470	$ 1,388	1,124
Loans, net	342,182	313,075
Commercial Real Estate Portfolio Segment | CRE investment | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 171,087	$ 113,862
% of Total	12.00%	9.00%
Less ALLL	$ 1,230	$ 1,154	893
Loans, net	169,857	112,708
Commercial Real Estate Portfolio Segment | CRE investment | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 172,565	$ 200,601
% of Total	25.00%	24.00%
Less ALLL	$ 240	$ 234	231
Loans, net	172,325	200,367
Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 80,599	$ 89,660
% of Total	4.00%	4.00%
Less ALLL	$ 510	$ 726	774
Loans, net	80,089	88,934
Commercial Real Estate Portfolio Segment | Construction & land development | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 66,478	$ 56,061
% of Total	4.00%	5.00%
Less ALLL	$ 431	$ 628	656
Loans, net	66,047	55,433
Commercial Real Estate Portfolio Segment | Construction & land development | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 14,121	$ 33,599
% of Total	2.00%	4.00%
Less ALLL	$ 79	$ 98	118
Loans, net	14,042	33,501
Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 357,841	$ 363,352
% of Total	17.00%	17.00%
Less ALLL	$ 1,646	$ 1,609	1,784
Loans, net	356,195	361,743
Residential | Residential first mortgage | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 220,368	$ 191,186
% of Total	15.00%	15.00%
Less ALLL	$ 1,400	$ 1,297	1,372
Loans, net	218,968	189,889
Residential | Residential first mortgage | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 137,473	$ 172,166
% of Total	20.00%	20.00%
Less ALLL	$ 246	$ 312	412
Loans, net	137,227	171,854
Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 111,328	$ 106,027
% of Total	5.00%	5.00%
Less ALLL	$ 472	$ 488	461
Loans, net	110,856	105,539
Residential | Residential junior mortgage | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 78,379	$ 65,643
% of Total	5.00%	5.00%
Less ALLL	$ 408	$ 409	373
Loans, net	77,971	65,234
Residential | Residential junior mortgage | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 32,949	$ 40,384
% of Total	5.00%	5.00%
Less ALLL	$ 64	$ 79	88
Loans, net	32,885	40,305
Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 30,926	$ 36,995
% of Total	1.00%	2.00%
Less ALLL	$ 211	$ 251	304
Loans, net	30,715	36,744
Residential | Residential construction | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 30,926	$ 33,615
% of Total	2.00%	3.00%
Less ALLL	$ 211	$ 200	266
Loans, net	30,715	33,415
Residential | Residential construction | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 0	$ 3,380
% of Total	0.00%	0.00%
Less ALLL	$ 0	$ 51	$ 38
Loans, net	$ 0	$ 3,329