Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Less: accumulated depreciation	$ (63,408)	$ (56,568)
Property and equipment, net	29,916	20,847
Depreciation and amortization of property and equipment	$ 8,023	7,593	$ 7,594
Minimum
Property and Equipment
Estimated useful life	3 years
Maximum
Property and Equipment
Estimated useful life	7 years
Computer equipment
Property and Equipment
Property and equipment, gross value	$ 3,061	2,991
Estimated useful life	3 years
Software
Property and Equipment
Property and equipment, gross value	$ 11,062	10,508
Estimated useful life	3 years
Office furniture and equipment
Property and Equipment
Property and equipment, gross value	$ 2,530	2,645
Office furniture and equipment | Minimum
Property and Equipment
Estimated useful life	5 years
Office furniture and equipment | Maximum
Property and Equipment
Estimated useful life	6 years
Laboratory equipment
Property and Equipment
Property and equipment, gross value	$ 51,315	47,938
Estimated useful life	7 years
Total gross carrying amount of certain lab and computer equipment disposed	$ 1,500
Accumulated depreciation on certain lab and computer equipment disposed	1,200
Leasehold improvements
Property and Equipment
Property and equipment, gross value	$ 25,356	$ 13,333