Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Abstract]
Cash	$ 1,542	$ 1,307
Cash equivalents:
Money market accounts	155,766	27,847
Total cash and cash equivalents	$ 157,308	$ 29,154	$ 32,555	$ 2,429