Property and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Less - accumulated depreciation	$ (14,630)	$ (15,857)
Property and equipment, net	2,616	1,776
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,963	9,801
Office and computer equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	2,968	3,288
Furniture, fixtures and fittings [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 4,315	$ 4,544