ALLOWANCE FOR LOAN LOSSES - Risk Grading (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Risk Grading
Risk rating of loans	$ 2,317,789	$ 2,160,046
Pass
Risk Grading
Risk rating of loans	2,255,908	2,083,745
Special Mention
Risk Grading
Risk rating of loans	19,571	19,328
Substandard
Risk Grading
Risk rating of loans	42,310	56,973
Commercial and industrial
Risk Grading
Risk rating of loans	559,363	511,554
Commercial and industrial | Pass
Risk Grading
Risk rating of loans	535,589	483,399
Commercial and industrial | Special Mention
Risk Grading
Risk rating of loans	8,403	2,207
Commercial and industrial | Substandard
Risk Grading
Risk rating of loans	15,371	25,948
Commercial real estate
Risk Grading
Risk rating of loans	738,293	697,794
Commercial real estate | Pass
Risk Grading
Risk rating of loans	722,503	674,445
Commercial real estate | Special Mention
Risk Grading
Risk rating of loans	2,951	7,731
Commercial real estate | Substandard
Risk Grading
Risk rating of loans	12,839	15,618
Construction and development
Risk Grading
Risk rating of loans	449,211	491,626
Construction and development | Pass
Risk Grading
Risk rating of loans	448,124	485,823
Construction and development | Special Mention
Risk Grading
Risk rating of loans	565	933
Construction and development | Substandard
Risk Grading
Risk rating of loans	522	4,870
One to four family residential
Risk Grading
Risk rating of loans	258,584	236,882
One to four family residential | Pass
Risk Grading
Risk rating of loans	252,317	234,473
One to four family residential | Special Mention
Risk Grading
Risk rating of loans		797
One to four family residential | Substandard
Risk Grading
Risk rating of loans	6,267	1,612
Multi‑family residential
Risk Grading
Risk rating of loans	220,305	133,210
Multi‑family residential | Pass
Risk Grading
Risk rating of loans	212,899	125,553
Multi‑family residential | Special Mention
Risk Grading
Risk rating of loans	7,406	7,650
Multi‑family residential | Substandard
Risk Grading
Risk rating of loans		7
Consumer
Risk Grading
Risk rating of loans	40,433	39,694
Consumer | Pass
Risk Grading
Risk rating of loans	40,144	39,684
Consumer | Special Mention
Risk Grading
Risk rating of loans	246	10
Consumer | Substandard
Risk Grading
Risk rating of loans	43
Agriculture
Risk Grading
Risk rating of loans	11,256	11,106
Agriculture | Pass
Risk Grading
Risk rating of loans	11,223	11,033
Agriculture | Substandard
Risk Grading
Risk rating of loans	33	73
Other
Risk Grading
Risk rating of loans	40,344	38,180
Other | Pass
Risk Grading
Risk rating of loans	33,109	29,335
Other | Substandard
Risk Grading
Risk rating of loans	$ 7,235	$ 8,845