Marketable securities as of September 30, 2024 and December 31, 2023 consist of both available-for-sale debt securities of investment grade issuers (see below and Note 6) as well as equity securities of publicly traded companies (see Note 6).


(In millions)	Amortized		Unrealized				Fair
As of September 30, 2024	Cost Basis		Gains		Losses		Value
Corporate bonds	$	7,708.2	$	83.5	$	(24.4)	$	7,767.3
U.S. government and government agency obligations	5,985.8		14.1		(1.3)		5,998.6
Sovereign bonds	66.7		0.4		(0.2)		66.9
Commercial paper	556.6		1.0		—		557.6
Certificates of deposit	402.1		1.0		—		403.1
Asset-backed securities	173.2		0.8		(0.1)		173.9
	$	14,892.6	$	100.8	$	(26.0)	$	14,967.4

As of December 31, 2023
Corporate bonds	$	6,492.5	$	10.4	$	(104.9)	$	6,398.0
U.S. government and government agency obligations	4,839.6		2.4		(8.6)		4,833.4
Sovereign bonds	58.1		—		(0.9)		57.2
Commercial paper	636.8		0.2		(0.2)		636.8
Certificates of deposit	520.8		0.6		—		521.4
Asset-backed securities	88.2		0.1		(1.2)		87.1
	$	12,636.0	$	13.7	$	(115.8)	$	12,533.9

The Company classifies its investments in available-for-sale debt securities based on their contractual maturity dates. The available-for-sale debt securities as of September 30, 2024 mature at various dates through October 2029. The fair values of available-for-sale debt securities by contractual maturity consist of the following:


	September 30,		December 31,
(In millions)	2024		2023
Maturities within one year	$	7,784.7	$	8,114.8
Maturities after one year through five years	7,181.9		4,414.5
Maturities after five years	0.8		4.6
	$	14,967.4	$	12,533.9

The following table shows the fair value and gross unrealized losses by category and disaggregated by the length of time that the Company's available-for-sale debt securities have been in a continuous unrealized loss position.


	Less than 12 Months				12 Months or Greater				Total
(In millions) As of September 30, 2024	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Corporate bonds	$	6,351.7	$	(0.7)	$	1,415.6	$	(23.7)	$	7,767.3	$	(24.4)
U.S. government and government agency obligations	5,799.9		(0.1)		198.7		(1.2)		5,998.6		(1.3)
Sovereign bonds	46.0		—		20.9		(0.2)		66.9		(0.2)
Asset-backed securities	141.6		—		32.3		(0.1)		173.9		(0.1)
	$	12,339.2	$	(0.8)	$	1,667.5	$	(25.2)	$	14,006.7	$	(26.0)

As of December 31, 2023
Corporate bonds	$	2,363.3	$	(2.4)	$	4,034.7	$	(102.5)	$	6,398.0	$	(104.9)
U.S. government and government agency obligations	4,780.6		(6.0)		52.7		(2.6)		4,833.3		(8.6)
Sovereign bonds	12.4		(0.1)		44.8		(0.8)		57.2		(0.9)
Commercial paper	636.8		(0.2)		—		—		636.8		(0.2)
Asset-backed securities	61.8		(0.3)		25.3		(0.9)		87.1		(1.2)
	$	7,854.9	$	(9.0)	$	4,157.5	$	(106.8)	$	12,012.4	$	(115.8)

The unrealized losses on corporate bonds were primarily driven by changes in interest rates. The Company has reviewed its portfolio of available-for-sale debt securities and determined that the decline in fair value below cost did not result from credit-related factors. In addition, the Company does not intend to sell, and it is not more likely than not that the Company will be required to sell, such securities before recovery of their amortized cost bases.

With respect to marketable securities, for the three and nine months ended September 30, 2024 and 2023, amounts reclassified from Accumulated other comprehensive income (loss) into Other income (expense), net were related to realized gains/losses on sales of available-for-sale debt securities. For the three and nine months ended September 30, 2024 and 2023, realized gains/losses on sales of marketable securities were not material.