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Marketable Securities (Tables)
 3 Months Ended
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Summary of Available for Sale Securities The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s marketable securities by major security type at each balance sheet date are summarized in the tables below (in thousands):
March 31, 2024
Amortized CostUnrealized Holding GainsUnrealized Holding LossesAggregate Fair Value
Short-term marketable securities:
U.S. government treasuries(1)
$829,902 $51 $(544)$829,409 
Corporate debt securities
1,079 — — 1,079 
Commercial paper
45,807 — — 45,807 
Total short-term marketable securities
876,788 51 (544)876,295 
Long-term marketable securities:
U.S. government treasuries(2)
475,612 — (416)475,196 
Corporate debt securities(3)
15,562 — (35)15,527 
Total long-term marketable securities
491,174 — (451)490,723 
Total
$1,367,962 $51 $(995)$1,367,018 
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(1)Unrealized holding losses on 23 securities with an aggregate fair value of $572.9 million.
(2)Unrealized holding losses on 14 securities with an aggregate fair value of $475.2 million.
(3)Unrealized holding losses on 4 securities with an aggregate fair value of $15.5 million.

December 31, 2023
Amortized CostUnrealized Holding GainsUnrealized Holding LossesAggregate Fair Value
Short-term marketable securities:
U.S. government treasuries
$868,174 $998 $— $869,172 
U.S. government agency securities(1)
7,089 — (3)7,086 
Commercial paper
31,147 — — 31,147 
Total
$906,410 $998 $(3)$907,405 
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(1)Unrealized holding losses on 2 securities with an aggregate fair value of $7.1 million.