Marketable Securities

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

All marketable securities were considered available-for-sale at March 31, 2024 and December 31, 2023. On a recurring basis, the Company records its marketable securities at fair value using Level 1 or Level 2 inputs as discussed in Note 2, "Fair Value Measurements". 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.

As of March 31, 2024 and December 31, 2023, some of the Company's marketable securities were in an unrealized loss position. The Company has not recognized an allowance for credit losses as of March 31, 2024 or December 31, 2023. The Company determined that it had the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. Further, a majority of these marketable securities are held in U.S. government securities, and the remainder were initially, and continue to be, held with investment grade, high credit quality institutions. All marketable securities with unrealized losses as of each balance sheet date have been in a loss position for less than twelve months or the loss is not material.

As of March 31, 2024, all of the Company’s marketable securities have an effective maturity of less than two years.