ALLOWANCE FOR LOAN LOSSES - Segregated by loan class (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loan losses segregated by loan class
Beginning balance	$ 24,778	$ 25,006	$ 25,006
Provision (recapture) for loan loss	865	960	(338)
Charge-offs	(472)	(508)	(1,125)
Recoveries	178	423	1,235
Net (charge-offs) recoveries	(294)	(85)	110
Ending balance	25,349	25,881	24,778
Specific reserve
Loan losses segregated by loan class
Beginning balance	1,035
Ending balance	1,007	500	1,035
General reserve
Loan losses segregated by loan class
Beginning balance	23,743
Ending balance	24,342	25,381	23,743
Commercial and industrial
Loan losses segregated by loan class
Beginning balance	7,257	6,409	6,409
Provision (recapture) for loan loss	479	1,454	642
Charge-offs	(469)	(508)	(904)
Recoveries	172	391	1,110
Net (charge-offs) recoveries	(297)	(117)	206
Ending balance	7,439	7,746	7,257
Commercial and industrial \| Specific reserve
Loan losses segregated by loan class
Beginning balance	852
Ending balance	845	364	852
Commercial and industrial \| General reserve
Loan losses segregated by loan class
Beginning balance	6,405
Ending balance	6,594	7,382	6,405
Commercial real estate
Loan losses segregated by loan class
Beginning balance	10,375	10,770	10,770
Provision (recapture) for loan loss	364	(266)	(284)
Charge-offs			(120)
Recoveries	3	3	9
Net (charge-offs) recoveries	3	3	(111)
Ending balance	10,742	10,507	10,375
Commercial real estate \| Specific reserve
Loan losses segregated by loan class
Beginning balance	64
Ending balance	55	52	64
Commercial real estate \| General reserve
Loan losses segregated by loan class
Beginning balance	10,311
Ending balance	10,687	10,455	10,311
Construction and development
Loan losses segregated by loan class
Beginning balance	3,482	4,598	4,598
Provision (recapture) for loan loss	(126)	(453)	(1,116)
Ending balance	3,356	4,145	3,482
Construction and development \| General reserve
Loan losses segregated by loan class
Beginning balance	3,482
Ending balance	3,356	4,145	3,482
1-4 family residential
Loan losses segregated by loan class
Beginning balance	1,326	1,286	1,286
Provision (recapture) for loan loss	5	(177)	35
Charge-offs	(3)		(8)
Recoveries	1	2	13
Net (charge-offs) recoveries	(2)	2	5
Ending balance	1,329	1,111	1,326
1-4 family residential \| Specific reserve
Loan losses segregated by loan class
Beginning balance	119
Ending balance	107		119
1-4 family residential \| General reserve
Loan losses segregated by loan class
Beginning balance	1,207
Ending balance	1,222	1,111	1,207
Multi‑family residential
Loan losses segregated by loan class
Beginning balance	1,419	916	916
Provision (recapture) for loan loss	101	(116)	503
Ending balance	1,520	800	1,419
Multi‑family residential \| General reserve
Loan losses segregated by loan class
Beginning balance	1,419
Ending balance	1,520	800	1,419
Consumer
Loan losses segregated by loan class
Beginning balance	566	353	353
Provision (recapture) for loan loss	(51)	235	263
Charge-offs			(93)
Recoveries	2	27	43
Net (charge-offs) recoveries	2	27	(50)
Ending balance	517	615	566
Consumer \| Specific reserve
Loan losses segregated by loan class
Ending balance		84
Consumer \| General reserve
Loan losses segregated by loan class
Beginning balance	566
Ending balance	517	531	566
Agriculture
Loan losses segregated by loan class
Beginning balance	68	79	79
Provision (recapture) for loan loss	(15)	(16)	(63)
Recoveries			52
Net (charge-offs) recoveries			52
Ending balance	53	63	68
Agriculture \| General reserve
Loan losses segregated by loan class
Beginning balance	68
Ending balance	53	63	68
Other
Loan losses segregated by loan class
Beginning balance	285	595	595
Provision (recapture) for loan loss	108	299	(318)
Recoveries			8
Net (charge-offs) recoveries			8
Ending balance	393	894	285
Other \| General reserve
Loan losses segregated by loan class
Beginning balance	285
Ending balance	393	$ 894	285
Unfunded Loan Commitment
Loan losses segregated by loan class
Beginning balance	378,000
Ending balance	$ 378,000		$ 378,000

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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