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Balance Sheet Details - Short-Term Investments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Short-term investments    
Amortized cost $ 111,161 $ 110,933
Unrealized gains 409 45
Unrealized losses (17) (311)
Estimated fair value 111,553 110,667
U.S. Government bonds    
Short-term investments    
Amortized cost   1,300
Unrealized losses   (3)
Estimated fair value   $ 1,297
U.S. Government bonds | Maximum    
Short-term investments    
Maturity   1 year
U.S. Government agency bonds    
Short-term investments    
Amortized cost   $ 1,994
Unrealized losses   (12)
Estimated fair value   $ 1,982
U.S. Government agency bonds | Maximum    
Short-term investments    
Maturity   1 year
Bank certificates of deposit    
Short-term investments    
Amortized cost 12,999 $ 15,201
Unrealized gains 7 2
Unrealized losses   (3)
Estimated fair value $ 13,006 $ 15,200
Bank certificates of deposit | Maximum    
Short-term investments    
Maturity 1 year 2 years
Commercial paper    
Short-term investments    
Amortized cost $ 7,475 $ 9,597
Unrealized gains 8 1
Unrealized losses   (5)
Estimated fair value $ 7,483 $ 9,593
Commercial paper | Maximum    
Short-term investments    
Maturity 1 year 1 year
Corporate notes    
Short-term investments    
Amortized cost $ 65,354 $ 60,923
Unrealized gains 295 24
Unrealized losses (10) (194)
Estimated fair value $ 65,639 $ 60,753
Corporate notes | Maximum    
Short-term investments    
Maturity 3 years 3 years
Asset-backed securities    
Short-term investments    
Amortized cost $ 25,333 $ 21,918
Unrealized gains 99 18
Unrealized losses (7) (94)
Estimated fair value $ 25,425 $ 21,842
Asset-backed securities | Maximum    
Short-term investments    
Maturity 3 years 3 years