PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 35,506	$ 35,141
Less - accumulated depreciation and amortization	(29,116)	(27,465)
Property, Plant and Equipment, Net	6,390	7,676
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,732	16,561
Furniture And Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,565	2,438
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,191	16,123
Equipment Under Construction [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 18	$ 19