Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Trade accounts payable	$ 37,758	$ 20,125
Accrued contract manufacturing expenses	11,663	0
Accrued employee related expenses	7,403	315
Clinical trial accruals	2,225	5,114
Executive severance liabilities	561	2,198
Miscellaneous other current liabilities	1,250	3,970
Accounts payable and accrued expenses	$ 60,860	$ 31,722