LOANS (Schedule of Loans Outstanding, by Classification) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Total loans	$ 3,439,650	$ 3,312,144
Unallocated Financing Receivables [Member]
Total loans	477	492
Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans	571,496	527,370
Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans	1,468,890	1,459,594
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans	573,253	551,233
Commercial Loans [Member] | Commercial Portfolio Segment [Member]
Total loans	687,677	636,714
Construction Loans [Member]
Total loans		1,405
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans	68,055	65,682
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other [Member]
Total loans	$ 69,802	$ 69,654
Loans and Finance Receivables [Member]
Total loans (in percent)	100.00%	100.00%
Loans and Finance Receivables [Member] | Unallocated Financing Receivables [Member]
Total loans (in percent)	0.01%	0.01%
Loans and Finance Receivables [Member] | Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	16.61%	15.92%
Loans and Finance Receivables [Member] | Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	42.71%	44.07%
Loans and Finance Receivables [Member] | Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans (in percent)	16.67%	16.65%
Loans and Finance Receivables [Member] | Commercial Loans [Member] | Commercial Portfolio Segment [Member]
Total loans (in percent)	19.99%	19.23%
Loans and Finance Receivables [Member] | Construction Loans [Member]
Total loans (in percent)		0.04%
Loans and Finance Receivables [Member] | Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	1.98%	1.98%
Loans and Finance Receivables [Member] | Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other [Member]
Total loans (in percent)	2.03%	2.10%