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Short-term Investments - Additional Information (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Short Term Investments [Abstract]        
Debt securities, impairment losses $ 0 $ 0 $ 0 $ 0
Debt securities, available-for-sale, realized gain (loss) $ 0 $ 0 $ 0 $ 0