Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued clinical trial expenses	$ 7,837	$ 6,683
Accrued compensation	12,197	6,937
Accrued professional fees	4,500	1,992
Accrued technical operation expenses	2,182	591
Accrued interest payable	423	438
Accrued construction costs	1,719	0
Other accrued expenses	481	181
Total accrued expenses	$ 29,339	$ 16,822