Inventory Valued at Lower of Cost (First-in, First-out) or Market, Net of Inventory Obsolescence Reserve (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory [Line Items]
Raw materials	$ 1,594	$ 1,596
Finished goods	52,403	56,836
Inventory, net	$ 53,997	$ 58,432