Accounts Receivable, Sales and Allowances - Net Trade Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Gross accounts receivable	$ 378,759	$ 519,175
Less reserves for:
Chargebacks	(73,984)	(80,360)
Rebates	(111,945)	(97,935)
Product returns	(41,687)	(43,689)
Discounts and allowances	(7,779)	(12,389)
Advertising and promotions	(1,301)	(688)
Doubtful accounts	(680)	(960)
Trade accounts receivable, net	$ 141,383	$ 283,154