Trade Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Receivables [Abstract]
Trade accounts receivable	$ 215,174	$ 139,910	$ 178,241
Allowance for doubtful accounts	(1,223)	(996)	(1,096)
Allowance for sales discounts and returns	(2,772)	(2,956)	(4,814)
Trade accounts receivable, net	211,179	$ 135,958	$ 172,331
Estimated refund liability	$ 1,300