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Cash, Cash Equivalents, and Marketable Debt Securities - Schedule of Marketable Debt Securities in Continuous Loss Position (Details)
$ in Millions
Sep. 30, 2021
USD ($)
Security
Dec. 31, 2020
USD ($)
Security
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 59.4 $ 48.1
Number of Marketable Debt Securities in a Loss Position | Security 76 62
Unrealized Losses [1] $ 0.0 $ 0.0
Corporate Debt Securities    
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 50.0 $ 42.9
Number of Marketable Debt Securities in a Loss Position | Security 63 56
Unrealized Losses [1] $ 0.0 $ 0.0
U.S. Government Agency Securities    
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 0.8 $ 0.0
Number of Marketable Debt Securities in a Loss Position | Security 2 0
Unrealized Losses [1] $ 0.0 $ 0.0
U.S. Treasury Securities    
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 8.1 $ 1.7
Number of Marketable Debt Securities in a Loss Position | Security 10 3
Unrealized Losses [1] $ 0.0 $ 0.0
Certificates of Deposit    
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 0.5 $ 1.3
Number of Marketable Debt Securities in a Loss Position | Security 1 2
Unrealized Losses [1] $ 0.0 $ 0.0
Commercial Paper    
Schedule Of Available For Sale Securities [Line Items]    
Fair Value of Marketable Debt Securities $ 0.0 $ 2.2
Number of Marketable Debt Securities in a Loss Position | Security 0 1
Unrealized Losses [1] $ 0.0 $ 0.0
[1] Unrealized losses were insignificant for the periods ended September 30, 2021 and December 31, 2020.