Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Commercial costs	$ 14,300	$ 0
Research costs	8,406	9,632
Payroll and employee benefits	16,934	9,338
Interest	3,482	0
Professional fees	6,295	7,532
Other current liabilities	95	95
Total accrued expenses and other current liabilities	$ 49,512	$ 26,597