DERIVATIVES AND HEDGING ACTIVITIES, Classification on Consolidated Statements of Financial Condition (Details) - Designated as Hedging Instrument [Member] $ in Thousands	Mar. 31, 2019 USD ($) DerivativeInstrument	Dec. 31, 2018 USD ($) DerivativeInstrument
Interest Rate Products [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Estimated reclassification decrease to interest expense during next twelve months	$ (907)
Interest Rate Swaps Related to FHLBNY Advances [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Count \| DerivativeInstrument	17	14
Notional amount	$ 295,000	$ 245,000
Fair value assets	3,258	4,669
Fair value liabilities	$ (3,970)	$ (2,097)

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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The number of derivative instruments of a particular group held by the entity.

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The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

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