Balance Sheet Components - Summary of Gross Unrealized Gains and Unrealized Losses of Investment Securities Excluding Investments in Money Market Funds (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 42,733	$ 87,036	$ 87,558	$ 25,287
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents		$ 33,200