LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY - Summary of loans by past due status (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 2,159,139	$ 2,072,198
Amount	$ 2,166,181	$ 2,087,925
Current - As a percent of total loans	99.70%	99.30%
As a percent of total loans	100.00%	100.00%
30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 1,571	$ 2,632
Finance Receivables 30 To 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Percent Past Due	0.10%	0.10%
90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 5,471	$ 13,095
Financing Receivable, Percent Past Due	0.20%	0.60%
Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 441,353	$ 430,043
Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	26,483	22,807
Amount	26,493	22,815
Retail & other | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	10	4
Retail & other | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	4
Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	682,104	631,110
Amount	684,920	637,337
Commercial Portfolio Segment | Commercial & industrial | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	211
Commercial Portfolio Segment | Commercial & industrial | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,816	6,016
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	440,123	428,839
Amount	441,353	430,043
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	557	671
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	673	533
Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	35,606	35,425
Amount	35,625	35,455
Commercial Portfolio Segment | Agricultural (“AG”) production | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	19	30
Commercial Portfolio Segment | Agricultural (“AG”) production | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	53,245	51,592
Amount	53,444	51,778
Commercial Real Estate Portfolio Segment | AG real estate | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	35	0
Commercial Real Estate Portfolio Segment | AG real estate | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	164	186
Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	343,262	309,932
Amount	343,652	314,463
Commercial Real Estate Portfolio Segment | CRE investment | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	180	0
Commercial Real Estate Portfolio Segment | CRE investment | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	210	4,531
Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	80,519	89,584
Amount	80,599	89,660
Commercial Real Estate Portfolio Segment | Construction & land development | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	76
Commercial Real Estate Portfolio Segment | Construction & land development | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	80	0
Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	355,818	360,726
Amount	357,841	363,352
Residential | Residential first mortgage | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	758	1,039
Residential | Residential first mortgage | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,265	1,587
Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	111,054	105,855
Amount	111,328	106,027
Residential | Residential junior mortgage | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	12	14
Residential | Residential junior mortgage | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	262	158
Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	30,925	36,328
Amount	30,926	36,995
Residential | Residential construction | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	587
Residential | Residential construction | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1	80
Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	1,485,165	1,243,702
Originated | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	23,809	18,254
Originated | Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	568,100	488,600
Originated | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	283,531	237,548
Originated | Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	11,113	11,102
Originated | Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	31,374	27,831
Originated | Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	171,087	113,862
Originated | Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	66,478	56,061
Originated | Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	220,368	191,186
Originated | Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	78,379	65,643
Originated | Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	30,926	33,615
Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	681,016	844,223
Acquired | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount		192,495
Acquired | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	2,684	4,561
Acquired | Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	116,820	148,737
Acquired | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	157,822	192,495
Acquired | Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	24,512	24,353
Acquired | Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	22,070	23,947
Acquired | Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	172,565	200,601
Acquired | Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	14,121	33,599
Acquired | Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	137,473	172,166
Acquired | Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	32,949	40,384
Acquired | Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount	$ 0	$ 3,380