Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued clinical trial and clinical supply costs	$ 17,398	$ 14,034
Accrued compensation	11,339	13,546
Accrued professional fees	3,703	3,706
Lease liabilities and related accrued interest, current	3,357	0
Accrued interest expense	629	650
Accrued product costs	13	38
Other accrued expenses	2,175	4,561
Total	$ 38,614	$ 36,535