Goodwill and Intangible Assets - Amortization Expense on Existing Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
Remainder of 2017	$ 78
2018	287
2019	260
2020	192
Total	$ 817	$ 969