LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY - Nonaccrual loans by portfolio segment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 5,471	$ 13,095
% to Non Accrual Total	100.00%	100.00%
Percent of nonaccrual loans	0.20%	0.60%
Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 4
% to Non Accrual Total	0.00%	0.00%
Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 2,816	$ 6,016
% to Non Accrual Total	52.00%	46.00%
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 673	$ 533
% to Non Accrual Total	12.00%	4.00%
Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 164	$ 186
% to Non Accrual Total	3.00%	1.00%
Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 210	$ 4,531
% to Non Accrual Total	4.00%	35.00%
Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 80	$ 0
% to Non Accrual Total	1.00%	0.00%
Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 1,265	$ 1,587
% to Non Accrual Total	23.00%	12.00%
Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 262	$ 158
% to Non Accrual Total	5.00%	1.00%
Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 1	$ 80
% to Non Accrual Total	0.00%	1.00%
Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 1,409	$ 3,278
% to Non Accrual Total	100.00%	100.00%
Percent of nonaccrual loans	25.80%	25.00%
Originated | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 4
% to Non Accrual Total	0.00%	0.00%
Originated | Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 352	$ 2,296
% to Non Accrual Total	25.00%	70.00%
Originated | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 362	$ 86
% to Non Accrual Total	26.00%	3.00%
Originated | Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Originated | Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Originated | Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 549
% to Non Accrual Total	0.00%	17.00%
Originated | Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Originated | Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 629	$ 331
% to Non Accrual Total	45.00%	10.00%
Originated | Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 65	$ 12
% to Non Accrual Total	4.00%	0.00%
Originated | Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 1	$ 0
% to Non Accrual Total	0.00%	0.00%
Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 4,062	$ 9,817
% to Non Accrual Total	100.00%	100.00%
Percent of nonaccrual loans	74.20%	75.00%
Acquired | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Acquired | Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 2,464	$ 3,720
% to Non Accrual Total	61.00%	38.00%
Acquired | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 311	$ 447
% to Non Accrual Total	8.00%	4.00%
Acquired | Commercial Portfolio Segment | Agricultural (“AG”) production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Non Accrual Total	0.00%	0.00%
Acquired | Commercial Real Estate Portfolio Segment | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 164	$ 186
% to Non Accrual Total	4.00%	2.00%
Acquired | Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 210	$ 3,982
% to Non Accrual Total	5.00%	41.00%
Acquired | Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 80	$ 0
% to Non Accrual Total	2.00%	0.00%
Acquired | Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 636	$ 1,256
% to Non Accrual Total	15.00%	13.00%
Acquired | Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 197	$ 146
% to Non Accrual Total	5.00%	1.00%
Acquired | Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 80
% to Non Accrual Total	0.00%	1.00%