Cash Equivalents and Marketable Securities

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Cash Equivalents and Marketable Securities

3. Cash Equivalents and Marketable Securities

Cash equivalents and available-for-sale debt securities consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):

	March 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	134,852	$	—	$	—	$	134,852
U.S. treasury securities	211,476		—		(6)		211,470
U.S. government agency securities	997		—		—		997
Corporate debt securities	41,811		—		—		41,811
Total cash equivalents	389,136		—		(6)		389,130
Debt securities:
U.S. treasury securities	292,446		67		(312)		292,201
U.S. government agency securities	334,264		56		(759)		333,561
Corporate debt securities	63,865		23		(111)		63,777
Certificates of deposit	49,770		—		—		49,770
Total debt securities	740,345		146		(1,182)		739,309
Total cash equivalents and debt securities	$	1,129,481	$	146	$	(1,188)	$	1,128,439

	December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	77,832	$	—	$	—	$	77,832
U.S. treasury securities	239,727		22		—		239,749
U.S. government agency securities	8,388		1		—		8,389
Corporate debt securities	36,905		—		—		36,905
Total cash equivalents	362,852		23		—		362,875
Debt securities:
U.S. treasury securities	264,554		339		(398)		264,495
U.S. government agency securities	366,946		571		(824)		366,693
Corporate debt securities	66,777		72		(109)		66,740
Total debt securities	698,277		982		(1,331)		697,928
Total cash equivalents and debt securities	$	1,061,129	$	1,005	$	(1,331)	$	1,060,803

The following table presents gross unrealized losses and fair values for the securities that were in a continuous unrealized loss position as of March 31, 2024 and December 31, 2023 (in thousands):

	March 31, 2024
	Less than 12 months				Greater than 12 months				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. treasury securities	$	212,189	$	(283)	$	14,958	$	(29)	$	227,147	$	(312)
U.S. government agency securities	216,579		(546)		62,696		(213)		279,275		(759)
Corporate debt securities	22,612		(92)		6,946		(19)		29,558		(111)
Total	$	451,380	$	(921)	$	84,600	$	(261)	$	535,980	$	(1,182)

	December 31, 2023
	Less Than 12 Months				12 Months or Greater				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. treasury securities	$	60,869	$	(159)	$	42,667	$	(239)	$	103,536	$	(398)
U.S. government agency securities	145,594		(364)		80,455		(460)		226,049		(824)
Corporate debt securities	14,749		(59)		12,934		(50)		27,683		(109)
Total	$	221,212	$	(582)	$	136,056	$	(749)	$	357,268	$	(1,331)

The amortized cost and fair value of the available-for-sale debt securities based on contractual maturities are as follows (in thousands):

	March 31, 2024
	Amortized Cost		Fair Value
Due within one year	$	584,728	$	583,797
Due after one year but within five years	155,617		155,512
Total	$	740,345	$	739,309

Accrued interest receivable of $3.9 million and $4.4 million was classified in prepaid expenses and other current assets in the condensed consolidated balance sheet as of March 31, 2024 and December 31, 2023, respectively.

In addition to available-for-sale debt securities, marketable securities also include term bond mutual funds, which are measured at fair value. As of March 31, 2024, we did not have any term bond mutual funds. As of December 31, 2023, the fair value of the term bond mutual funds was $1.6 million. The change in fair value of the term bond mutual funds is recorded in interest and other income, net in the condensed consolidated statements of operations. The realized and unrealized gains recognized in the condensed consolidated statements of operations were not material during the three months ended March 31, 2024 and 2023.