PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 35,141	$ 34,304
Less - accumulated depreciation and amortization	(27,465)	(25,601)
Property, Plant and Equipment, Net	7,676	8,703
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,561	16,265
Furniture And Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,438	2,342
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,123	15,678
Equipment Under Construction [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 19	$ 19