DERIVATIVES AND HEDGING ACTIVITIES - Additional Information (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) item	Dec. 31, 2020 USD ($)	Oct. 31, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Participating Mortgage Loans, Mortgage Obligations, Amount		$ 27,500
Number of Participation loans purchased | item		4
Interest Rate Swap | Cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount				$ 400,000
Derivative, Fixed Interest Rate				3.018%
Expected interest income on termination	$ 2,000
Not Designated as Hedging Instrument | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount		$ 124,700	$ 142,800
Number of Interest Rate Derivatives Held		14	19
Valley Bank | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of Loans Acquired | item		7
Valley Bank | Not Designated as Hedging Instrument | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of Loans Acquired | item		7
Number of Loans Paid Off | item		5
Derivative, Notional Amount		$ 534	$ 584
Number of Interest Rate Derivatives Held		2