LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY - Summary of information pertaining to impaired loans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	$ 9,939
Unpaid Principal Balance	16,021
Related Allowance	0
Average Recorded Investment	10,699
Interest Income Recognized	1,199
Impaired Financing Receivable
Recorded Investment	9,939	$ 17,221
Unpaid Principal Balance	16,021	26,948
Related Allowance	0	163
Average Recorded Investment	10,699	16,810
Interest Income Recognized	1,199	1,623
Retail & other
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	12
Unpaid Principal Balance	12
Related Allowance	0
Average Recorded Investment	12
Interest Income Recognized	1
Commercial Portfolio Segment \| Commercial & industrial
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	2,927
Unpaid Principal Balance	6,736
Related Allowance	0
Average Recorded Investment	4,041
Interest Income Recognized	660
Commercial Portfolio Segment \| Owner-occupied commercial real estate (“CRE”)
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	1,506
Unpaid Principal Balance	1,833
Related Allowance	0
Average Recorded Investment	1,659
Interest Income Recognized	137
Commercial Portfolio Segment \| Agricultural (“AG”) production
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Interest Income Recognized	0
Commercial Real Estate Portfolio Segment \| AG real estate
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	222
Unpaid Principal Balance	281
Related Allowance	0
Average Recorded Investment	238
Interest Income Recognized	26
Commercial Real Estate Portfolio Segment \| CRE investment
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	1,686
Unpaid Principal Balance	2,484
Related Allowance	0
Average Recorded Investment	1,606
Interest Income Recognized	163
Commercial Real Estate Portfolio Segment \| Construction & land development
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	603
Unpaid Principal Balance	1,506
Related Allowance	0
Average Recorded Investment	603
Interest Income Recognized	21
Residential \| Residential first mortgage
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	2,750
Unpaid Principal Balance	2,907
Related Allowance	0
Average Recorded Investment	2,478
Interest Income Recognized	176
Residential \| Residential junior mortgage
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	233
Unpaid Principal Balance	262
Related Allowance	0
Average Recorded Investment	62
Interest Income Recognized	15
Residential \| Residential construction
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Interest Income Recognized	0
Originated
Impaired Financing Receivable
Recorded Investment	548	3,003
Unpaid Principal Balance	548	3,003
Related Allowance	0	163
Average Recorded Investment	899	2,964
Interest Income Recognized	154	241
Acquired
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		17,221
Unpaid Principal Balance		26,948
Related Allowance		163
Average Recorded Investment		16,810
Interest Income Recognized		1,623
Impaired Financing Receivable
Recorded Investment	9,391	14,218
Unpaid Principal Balance	15,473	23,945
Related Allowance	0	0
Average Recorded Investment	9,800	13,846
Interest Income Recognized	$ 1,045	1,382
Acquired \| Retail & other
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		12
Unpaid Principal Balance		14
Related Allowance		0
Average Recorded Investment		12
Interest Income Recognized		1
Acquired \| Commercial Portfolio Segment \| Commercial & industrial
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		5,870
Unpaid Principal Balance		10,063
Related Allowance		163
Average Recorded Investment		6,586
Interest Income Recognized		718
Acquired \| Commercial Portfolio Segment \| Owner-occupied commercial real estate (“CRE”)
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		1,689
Unpaid Principal Balance		2,256
Related Allowance		0
Average Recorded Investment		1,333
Interest Income Recognized		132
Acquired \| Commercial Portfolio Segment \| Agricultural (“AG”) production
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		0
Unpaid Principal Balance		10
Related Allowance		0
Average Recorded Investment		0
Interest Income Recognized		0
Acquired \| Commercial Real Estate Portfolio Segment \| AG real estate
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		248
Unpaid Principal Balance		307
Related Allowance		0
Average Recorded Investment		233
Interest Income Recognized		26
Acquired \| Commercial Real Estate Portfolio Segment \| CRE investment
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		5,290
Unpaid Principal Balance		8,102
Related Allowance		0
Average Recorded Investment		5,411
Interest Income Recognized		465
Acquired \| Commercial Real Estate Portfolio Segment \| Construction & land development
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		1,053
Unpaid Principal Balance		1,053
Related Allowance		0
Average Recorded Investment		813
Interest Income Recognized		57
Acquired \| Residential \| Residential first mortgage
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		2,801
Unpaid Principal Balance		3,653
Related Allowance		0
Average Recorded Investment		2,177
Interest Income Recognized		180
Acquired \| Residential \| Residential junior mortgage
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		178
Unpaid Principal Balance		507
Related Allowance		0
Average Recorded Investment		154
Interest Income Recognized		17
Acquired \| Residential \| Residential construction
Impaired Financing Receivable, with No Realted Allowance
Recorded Investment		80
Unpaid Principal Balance		983
Related Allowance		0
Average Recorded Investment		91
Interest Income Recognized		$ 27

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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