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Marketable Securities - Summary of Investments (Details)
$ in Thousands
Dec. 31, 2020
USD ($)
security
Dec. 31, 2019
USD ($)
security
Marketable securities available-for-sale    
Amortization Cost $ 180,675 $ 121,103
Gross Unrealized Gains 7 39
Gross Unrealized Losses (9) (2)
Estimated Fair Value 180,673 121,140
Aggregate fair value of marketable securities with unrealized gains (losses) position for less than a year $ 45,700 $ 19,600
Number of investments in an unrealized loss position for less than a year | security 5 3
U.S. Treasury obligations    
Marketable securities available-for-sale    
Amortization Cost $ 180,675 $ 121,103
Gross Unrealized Gains 7 39
Gross Unrealized Losses (9) (2)
Estimated Fair Value $ 180,673 $ 121,140