Marketable Securities

6 Months Ended

Jun. 30, 2024

Investments, Debt and Equity Securities [Abstract]

The Company’s marketable securities, which consist of highly liquid marketable debt securities, are classified as available-for-sale and are stated at fair value. The following tables summarize the Company’s marketable securities (in thousands):


As of June 30, 2024	Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury securities	1 or less	$	613,201	$	6	$	(517)	$	612,690

Negotiable certificates of deposit	1 or less	1,959		—		(4)		1,955

U.S. Treasury securities	1 - 2	108,588		62		—		108,650


Total		$	723,748	$	68	$	(521)	$	723,295


As of December 31, 2023	Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury securities	1 or less	$	301,053	$	102	$	(530)	$	300,625
U.S. Government agency securities	1 or less	5,000		—		(2)		4,998
Negotiable certificates of deposit	1 or less	4,410		1		(4)		4,407

U.S. Treasury securities	1 - 2	98,701		600		(36)		99,265
Negotiable certificates of deposit	1 - 2	980		—		(6)		974
Total		$	410,144	$	703	$	(578)	$	410,269

The unrealized losses on the Company’s marketable securities were caused by interest rate increases and resulted in the decrease in market value of these securities. There were no allowances for credit losses at June 30, 2024 and December 31, 2023 because (i) the decline in fair value is attributable to changes in interest rates and not credit quality, (ii) the Company does not intend to sell the investments before maturity, and (iii) it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases.

The following table summarizes marketable securities in a continuous unrealized loss position for which an allowance for credit losses was not recorded (in thousands):


	Less Than 12 Months				12 Months or Greater				Total
As of June 30, 2024	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury securities	$	469,288	$	(312)	$	74,471	$	(205)	$	543,759	$	(517)

Negotiable certificates of deposit	734		—		1,221		(4)		1,955		(4)
Total	$	470,022	$	(312)	$	75,692	$	(209)	$	545,714	$	(521)


	Less Than 12 Months				12 Months or Greater				Total
As of December 31, 2023	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury securities	$	214,291	$	(566)	$	—	$	—	$	214,291	$	(566)
U.S. Government agency securities	4,998		(2)		—		—		4,998		(2)
Negotiable certificates of deposit	3,665		(10)		—		—		3,665		(10)
Total	$	222,954	$	(578)	$	—	$	—	$	222,954	$	(578)

Accrued interest receivable on available-for-sale securities was $4.1 million and $2.6 million at June 30, 2024 and December 31, 2023, respectively. The Company has not written off any accrued interest receivable for the six months ended June 30, 2024 and 2023.