Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accrued Expenses
Accrued manufacturing development costs	$ 8,529	$ 7,167
Accrued payroll, bonus and deferred compensation	2,929	3,841
Accrued construction in progress	3,374	2,979
Accrued clinical trial costs	1,036	389
Accrued professional fees	1,702	1,588
Other	1,322	830
Accrued expenses	$ 18,892	$ 16,794