FAIR VALUE OF FINANCIAL INSTRUMENTS, Balance Sheet Groupings (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets
Investment securities held to maturity (TRUPS)	$ 6,858	$ 7,051
Carrying Amount [Member]
Financial Assets
Cash and due from banks	80,870	64,154
Investment securities held to maturity (TRUPS)	5,356	5,242
Loans, net	5,470,117	4,678,262
Accrued interest receivable	15,192	13,486
FHLBNY capital stock	46,739	58,713
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,091,323	2,325,463
Certificates of Deposit ("CDs")	1,067,941	858,847
Escrow and other deposits	117,309	77,130
FHLBNY Advances	882,125	1,166,725
Trust preferred securities payable	70,680	70,680
Accrued interest payable	2,291	2,259
Fair Value [Member]
Financial Assets
Cash and due from banks	80,870	64,154
Investment securities held to maturity (TRUPS)	6,858	7,051
Loans, net	5,507,493	4,722,803
Accrued interest receivable	15,192	13,486
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,091,323	2,325,463
Certificates of Deposit ("CDs")	1,076,637	865,581
Escrow and other deposits	117,309	77,130
FHLBNY Advances	888,141	1,170,274
Trust preferred securities payable	70,327	69,973
Accrued interest payable	2,291	2,259
Fair Value [Member] | Level 1 Inputs [Member]
Financial Assets
Cash and due from banks	80,870	64,154
Investment securities held to maturity (TRUPS)	0	0
Loans, net	0	0
Accrued interest receivable	0	0
Financial Liabilities [Abstract]
Savings, money market and checking accounts	3,091,323	2,325,463
Certificates of Deposit ("CDs")	0	0
Escrow and other deposits	117,309	77,130
FHLBNY Advances	0	0
Trust preferred securities payable	0	0
Accrued interest payable	0	0
Fair Value [Member] | Level 2 Inputs [Member]
Financial Assets
Cash and due from banks	0	0
Investment securities held to maturity (TRUPS)	0	0
Loans, net	0	0
Accrued interest receivable	11	19
Financial Liabilities [Abstract]
Savings, money market and checking accounts	0	0
Certificates of Deposit ("CDs")	1,076,637	865,581
Escrow and other deposits	0	0
FHLBNY Advances	888,141	1,170,274
Trust preferred securities payable	70,327	69,973
Accrued interest payable	2,291	2,259
Fair Value [Member] | Level 3 Inputs [Member]
Financial Assets
Cash and due from banks	0	0
Investment securities held to maturity (TRUPS)	6,858	7,051
Loans, net	5,507,493	4,722,803
Accrued interest receivable	15,181	13,467
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
Trust preferred securities payable	0	0
Accrued interest payable	$ 0	$ 0