Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property and equipment
Property and equipment, gross	$ 82,951	$ 82,805
Less accumulated depreciation and amortization	(55,474)	(52,979)
Property and equipment, net	27,477	29,826
Manufacturing equipment
Property and equipment
Property and equipment, gross	3,623	3,623
Laboratory equipment
Property and equipment
Property and equipment, gross	14,819	15,126
Computer and office equipment
Property and equipment
Property and equipment, gross	5,208	5,185
Furniture and fixtures
Property and equipment
Property and equipment, gross	2,093	2,093
Software
Property and equipment
Property and equipment, gross	13,980	13,921
Construction in process
Property and equipment
Property and equipment, gross	193	1,457
Leased vehicles
Property and equipment
Property and equipment, gross	4,472	4,472
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 38,563	$ 36,928