FAIR VALUE OF FINANCIAL INSTRUMENTS, Balance Sheet Groupings (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying Amount [Member]
Financial Assets [Abstract]
Cash and due from banks	$ 188,826	$ 169,455
Loans, net (excluding impaired loans carried at fair value)	5,485,337	5,581,084
Accrued interest receivable	16,535	16,543
FHLBNY capital stock	52,514	59,696
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,205,950	3,311,560
Certificates of Deposit ("CDs")	1,224,491	1,091,887
Escrow and other deposits	131,953	82,168
FHLBNY Advances	1,010,400	1,170,000
Subordinated debt, net	113,649	113,612
Accrued interest payable	3,318	1,623
Fair Value [Member]
Financial Assets [Abstract]
Cash and due from banks	188,826	169,455
Loans, net (excluding impaired loans carried at fair value)	5,454,038	5,519,746
Accrued interest receivable	16,535	16,543
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,205,950	3,311,560
Certificates of Deposit ("CDs")	1,221,036	1,192,964
Escrow and other deposits	131,953	82,168
FHLBNY Advances	1,001,841	1,164,947
Subordinated debt, net	113,793	115,337
Accrued interest payable	3,318	1,623
Fair Value [Member] | Level 1 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	188,826	169,455
Loans, net (excluding impaired loans carried at fair value)	0	0
Accrued interest receivable	0	0
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,205,950	3,311,560
Certificates of Deposit ("CDs")	0	0
Escrow and other deposits	131,953	82,168
FHLBNY Advances	0	0
Subordinated debt, net	0	0
Accrued interest payable	0	0
Fair Value [Member] | Level 2 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	0	0
Loans, net (excluding impaired loans carried at fair value)	0	0
Accrued interest receivable	768	751
Financial Liabilities [Abstract]
Savings, money market and checking accounts	0	0
Certificates of Deposit ("CDs")	1,221,036	1,192,964
Escrow and other deposits	0	0
FHLBNY Advances	1,001,841	1,164,947
Subordinated debt, net	113,793	115,337
Accrued interest payable	3,318	1,623
Fair Value [Member] | Level 3 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	0	0
Loans, net (excluding impaired loans carried at fair value)	5,454,038	5,519,746
Accrued interest receivable	15,767	15,792
Financial Liabilities [Abstract]
Savings, money market and checking accounts	0	0
Certificates of Deposit ("CDs")	0	0
Escrow and other deposits	0	0
FHLBNY Advances	0	0
Subordinated debt, net	0	0
Accrued interest payable	$ 0	$ 0