Accrued Sales Deductions (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Sales Deductions
Accrued rebates	$ 85,003	$ 49,460
Accrued product returns	22,060	18,883
Accrued sales deductions, net	$ 107,063	$ 68,343