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Financial Instruments (Tables)
3 Months Ended
Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]  
Summary of Marketable Securities
Marketable securities classified as available-for-sale on March 31, 2022 and December 31, 2021, consisted of the following (in thousands):
March 31, 2022
MaturityAmortized CostUnrealized GainsUnrealized LossesFair Value
U.S. Treasury billsLess than one year$318,419 $— $(373)$318,047 

December 31, 2021
MaturityAmortized CostUnrealized GainsUnrealized LossesFair Value
U.S. Treasury billsLess than one year$416,559 $— $(50)$416,509