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Fair Value of Financial Instruments Including Cash, Cash Equivalents, and Investments - Schedule of Investments (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Fair Value Disclosures [Abstract]    
Certificates of deposit due in one year or less, Amortized Cost $ 90,000 $ 100,000
Held to maturity amortized cost 90,000 100,000
Certificates of deposit due in one year or less, Estimated Fair Value 90,000 100,000
Held to maturity fair value $ 90,000 $ 100,000