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Cash, Cash Equivalents, and Marketable Debt Securities - Additional Information (Details) - USD ($)
9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Financial Instruments [Line Items]    
Impairment of marketable debt securities $ 0 $ 0
Allowance for credit loss $ 0 $ 0
Minimum    
Financial Instruments [Line Items]    
Long-term marketable debt securities maturity period 1 year  
Maximum    
Financial Instruments [Line Items]    
Long-term marketable debt securities maturity period 2 years