DERIVATIVES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Derivative asset position net	$ 9,100		$ 9,100
Collateral received against obligations in net asset position	9,600		9,600
Interest rate swaps | Derivative designated as a cash flow hedge
Derivative [Line Items]
Notional amounts	265,000		265,000		$ 290,000
Interest rate swaps | Derivative designated as a cash flow hedge | Federal Home Loan Bank of New York [Member]
Derivative [Line Items]
Interest (income) expense on derivative	(374)	$ 369	(653)	$ 1,100
Reduction to interest expense			(653)
Reclassified estimated decrease in interest expense			2,200
Interest rate swaps related to FHLB advances | Derivative designated as a cash flow hedge
Derivative [Line Items]
Notional Amount	$ 265,000		$ 265,000		$ 290,000