Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash	$ 1,720	$ 1,576
Cash equivalents:
Money market accounts	120,962	148,604
Total cash and cash equivalents	$ 122,682	$ 150,180	$ 157,308	$ 29,154