Other Current Assets - Schedule of Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 1,519	$ 2,186
Advances to vendors	6,403	1,806
Other receivables	1,422	1,343
Total	$ 9,344	$ 5,335