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Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) - USD ($)
$ in Thousands
Jun. 30, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 107,481 $ 150,017
Gross Unrealized Holding Gains 872 439
Gross Unrealized Holding Losses (28) (49)
Fair Value 108,325 150,407
Corporate bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 86,266 126,550
Gross Unrealized Holding Gains 67 182
Gross Unrealized Holding Losses (28) (49)
Fair Value 86,305 126,683
Certificate of deposits [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,036 1,037
Gross Unrealized Holding Gains 0 0
Gross Unrealized Holding Losses 0 0
Fair Value 1,036 1,037
Bond and mutual funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 20,053 22,305
Gross Unrealized Holding Gains 744 157
Gross Unrealized Holding Losses 0 0
Fair Value 20,797 22,462
Equity investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 126 125
Gross Unrealized Holding Gains 61 100
Gross Unrealized Holding Losses 0 0
Fair Value $ 187 $ 225