Accrued Expenses & Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued expenses and other current liabilities:
Accrued compensation and benefits	$ 10,438	$ 7,886
Accrued consulting and professional fees	3,927	3,841
Accrued research and development	7,503	1,855
Accrued revenue reserves	10,155	0
Accrued other	6,358	5,357
Total accrued expenses and other current liabilities	$ 38,381	$ 18,939