LOANS RECEIVABLE AND CREDIT QUALITY, Credit Quality Indicators (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	$ 11,946	[1]	$ 16,141	[1]
Financing Receivable, Net	3,666,939		3,503,385
One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	11,946	[1]	16,141	[1]
Financing Receivable, Net	78,504		91,876
Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	0	[1]	0	[1]
Financing Receivable, Net	2,864,824		2,676,369
Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	0	[1]	0	[1]
Financing Receivable, Net	335,650		340,133
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	0	[1]	0	[1]
Financing Receivable, Net	387,662		394,531
Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	0	[1]	0	[1]
Financing Receivable, Net	299		476
Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	2,109		2,423
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	32,907		22,230
Special Mention [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	6,944		6,333
Special Mention [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	15,011		7,711
Special Mention [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	5,942		5,547
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	5,010		2,639
Special Mention [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	0		0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	34,034		43,837
Substandard [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	2,217		2,987
Substandard [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	4,262		3,248
Substandard [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	6,021		8,533
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	21,235		28,593
Substandard [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Individually Assigned Credit Rating	299		476
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	3,588,052		3,421,177
Pass [Member] | One-to four Family Residential and Cooperative Unit [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	57,397		66,415
Pass [Member] | Multifamily Residential and Residential Mixed Use [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	2,845,551		2,665,410
Pass [Member] | Mixed Use Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	323,687		326,053
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	361,417		363,299
Pass [Member] | Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	0		0
Pass [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	2,107		2,415
Non Accrual Financing Receivable [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Not Individually Assigned Credit Rating	$ 2		$ 8

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