Product Revenue - Accrued Sales Rebates and Returns (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Accrued Sales Rebates and Returns
Beginning balance		$ 3,997
Ending Balance	$ 687	687
Product
Accrued Sales Rebates and Returns
Beginning balance		3,997
Accrual	244	479
Payment		(3,789)
Ending Balance	$ 687	$ 687