Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Contract sales organization expenses	$ 4,482	$ 1,432
Research and development expenses	4,812	2,031
Selling, general and administrative expenses	933	80
Bonus expense	3,635	4,163
Payroll and benefit expenses	564	448
Employee contributions withheld	359	185
Product revenue allowances	2,856	0
Interest expense	345	45
Other	435	314
Accrued expenses	$ 18,421	$ 8,698