ALLOWANCE FOR LOAN LOSSES - Loan losses on the basis of Company's impairment methodology (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	$ 33,497	$ 29,655
Loans collectively evaluated for impairment	2,171,026	2,130,391
Total	2,204,523	2,160,046
Allowance allocated to specific reserves for loans individually evaluated for impairment	555	668
Commercial and industrial
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	11,782	12,315
Loans collectively evaluated for impairment	537,088	499,239
Total	548,870	511,554
Commercial real estate
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	11,350	6,264
Loans collectively evaluated for impairment	678,151	691,530
Total	689,501	697,794
Construction and development
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	265	476
Loans collectively evaluated for impairment	424,224	491,150
Total	424,489	491,626
One to four family residential
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	4,923	1,712
Loans collectively evaluated for impairment	241,641	235,170
Total	246,564	236,882
Multi‑family residential
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	1	7
Loans collectively evaluated for impairment	211,218	133,203
Total	211,219	133,210
Consumer
Allowance for loan losses on the basis of Company's impairment methodology
Loans collectively evaluated for impairment	42,772	39,694
Total	42,772	39,694
Agriculture
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment		36
Loans collectively evaluated for impairment	11,424	11,070
Total	11,424	11,106
Other
Allowance for loan losses on the basis of Company's impairment methodology
Loans individually evaluated for impairment	5,176	8,845
Loans collectively evaluated for impairment	24,508	29,335
Total	$ 29,684	$ 38,180

A valuation allowance for financing receivables that are expected to be uncollectible.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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