Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses and Other Current Liabilities
Accrued manufacturing development costs	$ 10,356	$ 7,167
Accrued payroll, bonus and deferred compensation	9,589	3,841
Accrued construction in progress	4,156	2,979
Accrued clinical trial costs	864	389
Accrued professional fees	5,406	1,588
Accrued loss on settlement	11,647
Other	2,920	830
Accrued expenses and other current liabilities	$ 44,938	$ 16,794