Revenue Recognition and Accounts Receivable - Schedule of Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue Recognition And Accounts Receivable [Abstract]
Product sales									$ 373,538	$ 355,652	$ 341,084
Marketing service fees									60,285	54,136	55,405
Net sales	$ 116,896	$ 105,247	$ 108,942	$ 102,738	$ 108,537	$ 98,497	$ 104,075	$ 98,679	$ 433,823	$ 409,788	$ 396,489