PREMISES AND EQUIPMENT - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) renewal_option	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Abstract]
Depreciation	$ 9,196	$ 9,519	$ 8,058
Initial lease terms	10 years
Number of lease renewal options | renewal_option	2
Operating leases, rent expense	$ 4,900	$ 4,500	$ 3,000