Accounts Receivable, Sales and Allowances - Net Trade Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Gross accounts receivable	$ 272,036	$ 308,305
Less reserves for:
Chargebacks	(41,092)	(55,312)
Rebates	(47,478)	(55,963)
Product returns	(33,114)	(35,146)
Discounts and allowances	(5,348)	(6,561)
Advertising and promotions	(1,549)	(1,574)
Doubtful accounts	(584)	(623)
Trade accounts receivable, net	$ 142,871	$ 153,126