Balance Sheet Components - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 116,128	$ 100,348	$ 107,824
Restricted cash included in other assets	300		187
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows	$ 116,428	$ 100,536	$ 108,011	$ 109,207