Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Expenses
Employee compensation expenses	$ 3,660	$ 5,293
Sales discounts and allowances	18,415	2,650
Selling and marketing expenses	741	453
Research and development expenses	2,036	1,437
Professional fees	407	1,123
Other	2,338	1,030
Total accrued expenses	$ 27,597	$ 11,986