Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued clinical expenses	$ 76,437	$ 71,881
Product revenue allowances	22,606	22,861
Professional fees	4,623	2,367
Lease liability	4,677
Accrued bonus	4,215	9,537
Accrued commercial manufacturing	3,118	6,383
Royalties	2,114	2,430
Accrued vacation	1,058	1,088
Accrued payroll	1,024	2,255
Merger costs	799	16,071
Accrued severance	202	3,962
Accrued other	16,930	12,082
Total accrued expenses	$ 137,803	$ 150,917