LOANS (Schedule of Loans Outstanding, by Classification) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Dec. 31, 2015	Jun. 30, 2016
Total loans	$ 2,913,242	$ 3,148,899
Unallocated Financing Receivables [Member]
Total loans	500	430
Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans	470,869	479,839
Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans	1,416,775	1,501,915
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans	413,118	459,744
Commercial Loans [Member] | Commercial Portfolio Segment [Member]
Total loans	512,886	576,169
Construction Loans [Member]
Total loans	1,401
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans	52,649	63,188
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other [Member]
Total loans	$ 45,044	$ 67,614
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)	0.02%	0.01%
Loans and Finance Receivables [Member] | Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	16.16%	15.24%
Loans and Finance Receivables [Member] | Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	48.63%	47.70%
Loans and Finance Receivables [Member] | Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans (in percent)	14.18%	14.60%
Loans and Finance Receivables [Member] | Commercial Loans [Member] | Commercial Portfolio Segment [Member]
Total loans (in percent)	17.60%	18.30%
Loans and Finance Receivables [Member] | Construction Loans [Member]
Total loans (in percent)	0.05%
Loans and Finance Receivables [Member] | Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans (in percent)	1.81%	2.01%
Loans and Finance Receivables [Member] | Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other [Member]
Total loans (in percent)	1.55%	2.14%