FEDERAL HOME LOAN BANK ADVANCES AND OTHER BORROWINGS (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Advances from Federal Home Loan Banks	$ 37,898	$ 61,800
FHLB interest rate	2.20%	2.02%
Advances with fixed maturity dates	$ 28,900	$ 49,800
Weighted average interest rate on fixed maturity advances	1.96%	1.78%
Residential mortgages pledged as collateral for advances	$ 550,000	$ 468,300
Multifamily mortgage loans pledged as collateral for advances	1,100,000	1,200,000
Callable variable rate advances	$ 9,000	$ 12,000
Weighted average interest rate on variable advances (in percent)	2.95%	3.01%
Investment pledges against advances	$ 13,500	$ 14,600
Overnight borrowings of debt
Unused commitments from FHLB	1,200,000
Unused short-term or overnight borrowings from correspondent banks	22,000
Unused short-term or overnight borrowings from FRB	$ 785,600