Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued clinical	$ 63,046	$ 61,815
Product revenue allowances	40,975	30,552
Accrued payroll	9,486	12,604
MTPC - Supply of Validation Drug Product	6,441	0
Lease liability	5,206	4,989
Royalties	2,815	2,713
Accrued commercial manufacturing	2,676	2,680
Professional fees	1,747	3,444
Accrued severance	712	725
Accrued other	9,728	9,549
Total accrued expenses	$ 142,832	$ 129,071