Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Available-for-sale Debt Securities

The following tables summarize the Company's investments in available-for-sale debt securities:

(In millions)	Amortized		Unrealized				Fair
As of March 31, 2024	Cost Basis		Gains		Losses		Value
Corporate bonds	$	7,478.9	$	6.1	$	(83.9)	$	7,401.1
U.S. government and government agency obligations	5,291.2		0.4		(18.2)		5,273.4
Sovereign bonds	59.8		—		(0.8)		59.0
Commercial paper	867.1		0.3		(0.5)		866.9
Certificates of deposit	389.7		0.2		—		389.9
Asset-backed securities	126.0		—		(1.3)		124.7
	$	14,212.7	$	7.0	$	(104.7)	$	14,115.0
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

Marketable Securities, Based on Contractual Maturity Dates

The fair values of available-for-sale debt securities by contractual maturity consist of the following:

	March 31,		December 31,
(In millions)	2024		2023
Maturities within one year	$	7,917.5	$	8,114.8
Maturities after one year through five years	6,184.1		4,414.5
Maturities after five years	13.4		4.6
	$	14,115.0	$	12,533.9

Fair Value and Unrealized Losses of Marketable Securities

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

	Less than 12 Months				12 Months or Greater				Total
(In millions) As of March 31, 2024	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate bonds	$	4,490.4	$	(10.7)	$	2,910.7	$	(73.2)	$	7,401.1	$	(83.9)
U.S. government and government agency obligations	5,220.4		(15.9)		53.0		(2.3)		5,273.4		(18.2)
Sovereign bonds	32.5		(0.2)		26.5		(0.6)		59.0		(0.8)
Commercial paper	866.9		(0.5)		—		—		866.9		(0.5)
Asset-backed securities	99.2		(0.6)		25.5		(0.7)		124.7		(1.3)
	$	10,709.4	$	(27.9)	$	3,015.7	$	(76.8)	$	13,725.1	$	(104.7)
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)