DERIVATIVES AND HEDGING ACTIVITIES, Classification on Consolidated Statements of Financial Condition (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($) DerivativeInstrument	Sep. 30, 2019 USD ($) DerivativeInstrument	Dec. 31, 2018 USD ($) DerivativeInstrument
Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Loan level derivative income	$ 197	$ 488
Posted collateral	1,640	1,640
Interest Rate Products [Member] \| Designated as Hedging Instrument [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Estimated reclassification decrease to interest expense during next twelve months	$ (1,163)	$ (1,163)
Interest Rate Swaps Related to FHLBNY Advances [Member] \| Designated as Hedging Instrument [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Count \| DerivativeInstrument	24	24	14
Notional amount	$ 425,000	$ 425,000	$ 245,000
Fair value assets	730	730	4,669
Fair value liabilities	$ (9,842)	$ (9,842)	$ (2,097)
Loan Level Interest Rate Swaps with Borrower [Member] \| Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Count \| DerivativeInstrument	4	4
Notional amount	$ 39,984	$ 39,984
Fair value assets	1,696	1,696
Fair value liabilities	$ 0	$ 0
Loan Level Interest Rate Swaps with Third-part Counterparties [Member] \| Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Financial Instruments [Abstract]
Count \| DerivativeInstrument	4	4
Notional amount	$ 39,984	$ 39,984
Fair value assets	0	0
Fair value liabilities	$ 1,696	$ 1,696

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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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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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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Nominal or face amount used to calculate payment on derivative.

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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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