LOANS AND LEASES (Schedule of Loans Outstanding, by Classification) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Total loans	$ 3,897,416	$ 3,927,931
Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	100.00%	100.00%
Unallocated Financing Receivables [Member]
Total loans	$ 355	$ 465
Unallocated Financing Receivables [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	0.01%	0.01%
Residential Mortgage [Member] | Residential Portfolio Segment [Member]
Total loans	$ 569,304	$ 571,570
Residential Mortgage [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	14.61%	14.55%
Multifamily Property [Member] | Residential Portfolio Segment [Member]
Total loans	$ 1,104,406	$ 1,135,805
Multifamily Property [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	28.34%	28.92%
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans	$ 705,221	$ 702,165
Commercial Mortgage [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	18.09%	17.88%
Commercial Loans Including Equipment Financing [Member] | Commercial Real Estate Portfolio Segment [Member]
Total loans	$ 1,406,215	$ 1,397,057
Commercial Loans Including Equipment Financing [Member] | Commercial Real Estate Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	36.08%	35.57%
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member]
Total loans	$ 57,639	$ 62,191
Home Equity Lines of Credit [Member] | Residential Portfolio Segment [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	1.48%	1.58%
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other Loans [Member]
Total loans	$ 54,276	$ 58,678
Consumer Loans, Including Home Equity Loans [Member] | Consumer and Other Loans [Member] | Loans and Finance Receivables, Gross [Member] | Credit Concentration Risk [Member]
Total loans (in percent)	1.39%	1.49%