Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued Expenses
Accrued cost of product revenues	$ 14,540
Accrued bonuses	1,828	$ 2,940
Accrued incentive compensation	1,643	1,790
Accrued other operating costs	1,433	877
Accrued payroll and related benefits	1,401	1,382
Accrued inventory	1,385
Accrued audit and legal	551	405
Accrued sales and marketing	259	624
Accrued development costs	202	517
Accrued interest	153	6
Total accrued expenses	$ 23,395	$ 8,541