DERIVATIVES - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Notional amounts	$ 1,100,000	$ 823,900
Derivative liability position net	0
Derivative asset position net	57,100
Collateral received against obligations in net asset position	57,900
Collateral posted in net liability position	0
Derivative designated as a cash flow hedge | Amount Reclassified from Accumulated Other Comprehensiven (loss) Income
Derivative [Line Items]
Accelerated reclassification, loss from other comprehensive income to earnings as a result of the hedged forecasted transactions becoming probable not to occur	3,400
Interest rate swaps | Derivative designated as a cash flow hedge
Derivative [Line Items]
Notional amounts	280,000	290,000
Notional amount terminated	$ 125,000
Derivative, number of terminations | contract	4
Loss on termination of swaps, reported in non-interest income	$ 3,400
Interest income (expense) on derivative	1,700	$ 1,600	$ 1,100
Interest rate swaps | Derivative designated as a cash flow hedge | Federal Home Loan Bank of New York
Derivative [Line Items]
Reclassified as an increase to interest expense during the next twelve months	2,100
Interest rate swaps | Derivative designated as a cash flow hedge | Federal Home Loan Bank of New York | Amount Reclassified from Accumulated Other Comprehensiven (loss) Income
Derivative [Line Items]
Increase to interest expense	$ 1,700