FAIR VALUE OF FINANCIAL INSTRUMENTS, Balance Sheet Groupings (Details) $ in Thousands	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Security
Financial Assets [Abstract]
TRUP CDOs		$ 7,296
Financial Liabilities [Abstract]
Trust preferred securities collateralized mortgage obligations, number | Security		7
Carrying Amount [Member]
Financial Assets [Abstract]
Cash and due from banks	$ 169,455	$ 113,503
TRUP CDOs		5,378
Loans, net	5,581,084	5,615,886
Accrued interest receivable	16,543	15,647
FHLBNY capital stock	59,696	44,444
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,311,560	3,346,961
CDs	1,091,887	1,048,465
Escrow and other deposits	82,168	103,001
FHLBNY advances	1,170,000	831,125
Subordinated debt, net	113,612
Trust Preferred securities payable		70,680
Accrued interest payable	1,623	2,080
Fair Value [Member]
Financial Assets [Abstract]
Cash and due from banks	169,455	113,503
TRUP CDOs		7,296
Loans, net	5,519,746	5,609,034
Accrued interest receivable	16,543	15,647
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,311,560	3,346,961
CDs	1,192,964	1,054,131
Escrow and other deposits	82,168	103,001
FHLBNY advances	1,164,947	831,951
Subordinated debt, net	115,337
Trust Preferred securities payable		69,973
Accrued interest payable	1,623	2,080
Fair Value [Member] | Level 1 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	169,455	113,503
TRUP CDOs		0
Loans, net	0	0
Accrued interest receivable	0	0
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,311,560	3,346,961
CDs	0	0
Escrow and other deposits	82,168	103,001
FHLBNY advances	0	0
Subordinated debt, net	0
Trust Preferred securities payable		0
Accrued interest payable	0	0
Fair Value [Member] | Level 2 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	0	0
TRUP CDOs		0
Loans, net	0	0
Accrued interest receivable	751	11
Financial Liabilities [Abstract]
Savings, money market and checking accounts	0	0
CDs	1,192,964	1,054,131
Escrow and other deposits	0	0
FHLBNY advances	1,164,947	831,951
Subordinated debt, net	115,337
Trust Preferred securities payable		69,973
Accrued interest payable	1,623	2,080
Fair Value [Member] | Level 3 Inputs [Member]
Financial Assets [Abstract]
Cash and due from banks	0	0
TRUP CDOs		7,296
Loans, net	5,519,746	5,609,034
Accrued interest receivable	15,792	15,636
Financial Liabilities [Abstract]
Savings, money market and checking accounts	0	0
CDs	0	0
Escrow and other deposits	0	0
FHLBNY advances	0	0
Subordinated debt, net	0
Trust Preferred securities payable		0
Accrued interest payable	$ 0	$ 0