Summary of Significant Accounting Policies - Inventory Valued at Lower of Cost (First-in, First-out) or Market, Net of Inventory Obsolescence Reserve (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Raw materials	$ 311	$ 477
Finished goods	53,569	57,955
Inventory, net	53,880	58,432
Inventory obsolescense reserve	$ 12,800	$ 14,400