v3.20.4
Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash, Cost or Amortized Cost $ 545,618 $ 520,317
Fair Value, Measurements, Recurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and Marketable securities, Cost or Amortized Cost 2,537,472 2,112,225
Cash and Marketable securities, Gross Unrealized Gains 131 665
Cash and Marketable securities, Gross Unrealized Losses (63) (85)
Cash and Marketable Securities, Total Estimated Fair Value 2,537,540 2,112,805
Fair Value, Measurements, Recurring | Cash    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash, Cost or Amortized Cost 464,006 416,099
Cash, Total Estimated Fair Value 464,006 416,099
Fair Value, Measurements, Recurring | Level 1 Securities | U.S. Government Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Marketable securities, Cost or Amortized Cost 1,272,125 1,305,145
Marketable securities, Gross Unrealized Gains 122 604
Marketable securities, Gross Unrealized Losses (21) (49)
Marketable securities, Total Estimated Fair Value 1,272,226 1,305,700
Fair Value, Measurements, Recurring | Level 1 Securities | U.S. Government Agency Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Marketable securities, Cost or Amortized Cost 245,055 269,278
Marketable securities, Gross Unrealized Gains 8 48
Marketable securities, Gross Unrealized Losses (24) (32)
Marketable securities, Total Estimated Fair Value 245,039 269,294
Fair Value, Measurements, Recurring | Level 2 Securities | Corporate Debt Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Marketable securities, Cost or Amortized Cost 81,158 28,420
Marketable securities, Gross Unrealized Gains 1 13
Marketable securities, Gross Unrealized Losses (18) (4)
Marketable securities, Total Estimated Fair Value 81,141 28,429
Fair Value, Measurements, Recurring | Level 2 Securities | Commercial Paper    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Marketable securities, Cost or Amortized Cost 425,861 84,498
Marketable securities, Total Estimated Fair Value 425,861 84,498
Fair Value, Measurements, Recurring | Level 2 Securities | Certificates of Deposit    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Marketable securities, Cost or Amortized Cost 49,267 8,785
Marketable securities, Total Estimated Fair Value $ 49,267 $ 8,785