COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Rental expense under operating leases	$ 2.2	$ 2.2	$ 2.5
Additional FHLB advances available	237.8	$ 240.9
Federal Home Loan Bank advances
Line of Credit Facility [Line Items]
Additional FHLB advances available	237.8
Line of credit
Line of Credit Facility [Line Items]
Amount of federal funds lines of credit available through correspondent banks	33.5
Federal Reserve Bank advances
Line of Credit Facility [Line Items]
Loan collateral pledged	$ 171.1