FHLBNY ADVANCES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Average interest cost	1.63%	1.45%	1.65%
FHLBNY borrowing capacity	$ 1,770,671	$ 2,096,600
Callable advances	0
FHLBNY Advances prepaid	0	0	$ 25,000
Expense incurred on borrowing prepayment			$ 1,362
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
2018	667,100
2019	186,150
2020	263,750
2021	53,000
Total	$ 1,170,000	$ 831,125
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due [Abstract]
2018	1.57%
2019	1.68%
2020	1.85%
2021	2.03%
Weighted Average [Member]
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due [Abstract]
Interest rate on outstanding FHLBNY advances	1.67%	1.57%