Accrued Expenses and Other Long-term Liabilities - Schedule of Other Long-term Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Liabilities, Noncurrent [Abstract]
Aquisition-related liabilities	$ 1,115	$ 127
Deferred rent	539	561
Income taxes	318	321
Other	195	179
Total	$ 2,167	$ 1,188