Balance Sheet Components - Summary of Gross Unrealized Gains and Unrealized Losses of Investment Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 114,253	$ 139,691
Gross Unrealized Holding Gains	186	132
Gross Unrealized Holding Losses	0	0
Aggregate Fair Value	114,439	139,823
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	103,707	129,075
Gross Unrealized Holding Gains	181	131
Gross Unrealized Holding Losses	0	0
Aggregate Fair Value	103,888	129,206
Treasury Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,546	10,616
Gross Unrealized Holding Gains	5	1
Gross Unrealized Holding Losses	0	0
Aggregate Fair Value	$ 10,551	$ 10,617