Inventories and Other Deferred Costs - Summary of Inventories and Other Deferred Costs (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 3,549	$ 3,200
Work-in-process	4,253	3,745
Finished products	12,668	12,278
Other deferred costs	1,199	1,823
Total inventory and other deferred costs	$ 21,669	$ 21,046