Inventory and Other Deferred Costs - Summary of Inventory and Other Deferred Costs (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 3,200	$ 2,810
Work-in-process	3,745	2,489
Finished products	12,278	11,662
Other deferred costs	1,823	2,617
Total inventory and other deferred costs	$ 21,046	$ 19,578