Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Expenses
Accrued cost of product revenues	$ 6,710
Accrued incentive compensation	2,937	$ 1,790
Accrued inventory	2,367
Accrued payroll and related benefits	1,579	1,382
Accrued other operating costs	719	624
Accrued bonuses	1,453	877
Accrued sales and marketing	883	2,940
Accrued audit and legal	554	405
Accrued development costs	136	517
Accrued interest	98	6
Total accrued expenses	$ 17,436	$ 8,541