DERIVATIVES - Cash Flow Hedges included in the Consolidated Balance Sheets (Details) - Derivative designated as a cash flow hedge - Interest rate swaps related to FHLB advances - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 265,000	$ 290,000
Fair Value Asset	6,510	3,133
Fair Value Liability	$ (9)	$ (410)