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Cash Equivalents and Short-term and Long-term Investments - Narrative (Details) - USD ($)
Sep. 30, 2020
Dec. 31, 2019
Cash and Cash Equivalents [Abstract]    
Continuous unrealized loss position, twelve months or longer, fair value $ 0 $ 0
Unrealized loss position, less than twelve months, fair value $ 18,000 35,800,000
Continuous unrealized loss position, fair value   $ 0