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 Cost		Unrealized Holding Gains		Unrealized Holding Losses		Aggregate 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 Cost		Unrealized Holding Gains		Unrealized Holding Losses		Aggregate 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.