DERIVATIVES AND HEDGING ACTIVITIES, Offsetting of Derivative Assets (Details) - Other Assets [Member] - Interest Rate Swaps Related to FHLBNY Advances [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	$ 6,117	$ 4,041
Gross Amounts Offset in the Consolidated Statement of Financial Condition	(78)	0
Net amounts of assets presented in the statements of financial condition	6,039	4,041
Gross amounts not offset in the statement of financial position, financial instruments	0	0
Gross amounts not offset in the statement of financial position, cash collateral received	0	0
Net amount	$ 6,039	$ 4,041