LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY - Summary of allowance for loan losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ALLL:
Beginning balance	$ 12,653	$ 11,820	$ 10,307
Provision for loan losses	1,600	2,325	1,800
Charge-offs	(1,213)	(1,604)	(584)
Recoveries	113	112	297
Net charge-offs	(1,100)	(1,492)	(287)
Ending balance	$ 13,153	$ 12,653	$ 11,820