Prepaid Expenses and Other Current Assets - Components of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid services	$ 533	$ 837
Other prepaid contracts	2,132	2,293
Restricted cash	240	265
Other	327	316
Total	$ 3,232	$ 3,711