LOANS, Credit Quality Indicator (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	$ 7,698	$ 9,091
Financing Receivable, Net		72,095	73,500
Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	0	0
Financing Receivable, Net		3,759,907	3,298,448
Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	0	0
Financing Receivable, Net		377,275	328,667
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	0	0
Financing Receivable, Net		485,909	416,796
Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	0	0
Financing Receivable, Net		0	0
Total Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating	[1]	7,698	9,091
Financing Receivable, Net		4,695,186	4,117,411
Pass [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		61,256	60,764
Pass [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		3,743,298	3,271,430
Pass [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		370,110	317,718
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		473,242	391,227
Pass [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Pass [Member] | Total Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		4,647,906	4,041,139
Special Mention [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		945	1,370
Special Mention [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		9,759	20,738
Special Mention [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		1,622	4,944
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		4,857	6,431
Special Mention [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Special Mention [Member] | Total Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		17,183	33,483
Substandard [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		2,196	2,275
Substandard [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		6,850	6,280
Substandard [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		5,543	6,005
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		7,810	19,138
Substandard [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Substandard [Member] | Total Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		22,399	33,698
Doubtful [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Doubtful [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Doubtful [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Doubtful [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Doubtful [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Doubtful [Member] | Total Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total real estate loans individually assigned a credit rating		0	0
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating		1,590	1,829
Consumer Loans [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating		1,586	1,825
Consumer Loans [Member] | Non-accrual Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Real estate loans not individually assigned a credit rating		$ 4	$ 4

[1] Amount comprised of fully performing one- to four-family residential and condominium or cooperative apartment loans with balances equal to or less than the FNMA Limits.