Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Summary of assets and liabilities recorded at fair value

The tables below present information about our assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques we utilized to determine such fair value:

	Fair Value Measurements on a Recurring Basis
	As of December 31, 2025
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,233.2	$	—	$	2,233.2	$	—
Marketable debt securities:
Corporate debt securities	537.6		—		537.6		—
Government securities	648.8		—		648.8		—
Mortgage and other asset backed securities	52.7		—		52.7		—
Marketable equity securities	118.1		118.1		—		—
Other current assets:
Derivative contracts	10.0		—		10.0		—
Other non-current assets:
Convertible notes(1)	35.0		—		—		35.0
Plan assets for deferred compensation	52.2		—		52.2		—
Derivative contracts	0.4		—		0.4		—
Total	$	3,688.0	$	118.1	$	3,534.9	$	35.0
Liabilities:
Other current liabilities:
Derivative contracts	$	56.7	$	—	$	56.7	$	—
Other non-current liabilities:
Derivative contracts	2.2		—		2.2		—
Contingent consideration obligations	246.4		—		—		246.4
Total	$	305.3	$	—	$	58.9	$	246.4

(1) Convertible notes includes a $30.0 million convertible note we invested in as part of our strategic research arrangement with City Therapeutics during 2025, as well as a $5.0 million convertible note we invested into Neela Therapeutics, Inc. during 2025. We elected the fair value option for both convertible notes. For additional information on the arrangement with City Therapeutics, please read Note 19, Collaborative and Other Relationships, to these consolidated financial statements.

	Fair Value Measurements on a Recurring Basis
	As of December 31, 2024
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,664.9	$	—	$	1,664.9	$	—
Marketable equity securities	179.7		179.7		—		—
Other current assets:
Derivative contracts	62.5		—		62.5		—
Other non-current assets:
Plan assets for deferred compensation	42.8		—		42.8		—
Total	$	1,949.9	$	179.7	$	1,770.2	$	—
Liabilities:
Other current liabilities:
Derivative contracts	$	11.7	$	—	$	11.7	$	—
Contingent consideration obligations	291.2		—		—		291.2
Other non-current liabilities:
Contingent consideration obligations	221.6		—		—		221.6
Total	$	524.5	$	—	$	11.7	$	512.8

Fair value measurement inputs and valuation techniques

The following tables present quantitative information, as of the dates indicated, about the valuation techniques and significant unobservable inputs used in the valuation of our Level 3 financial assets and liabilities measured at fair value on a recurring basis:

	Quantitative Information about Level 3 Fair Value Measurements
	As of December 31, 2025
(In millions)	Fair Value		Valuation Technique	Significant Unobservable Input(s)	Range	Weighted Average
Liabilities:
Contingent consideration obligations	$	246.4	Discounted cash flow	Discount rate	5.3% - 5.4%	5.4%
				Expected timing of achievement of development milestones	2028 - 2030	—

	Quantitative Information about Level 3 Fair Value Measurements
	As of December 31, 2024
(In millions)	Fair Value		Valuation Technique	Significant Unobservable Input(s)	Range	Weighted Average
Liabilities:
Contingent consideration obligations	$	512.8	Discounted cash flow	Discount rate	6.2% - 6.3%	6.2%
				Expected timing of achievement of development milestones	2025 - 2030	—

Fair value of contingent consideration obligations

The following table provides a roll forward of the fair value of our contingent consideration obligations, which were classified as Level 3 measurements:

	As of December 31,
(In millions)	2025		2024
Fair value, beginning of year	$	512.8	$	—
Contingent consideration resulting from HI-Bio acquisition	—		485.1
Changes in fair value	33.6		27.7
Payments	(300.0)		—
Fair value, end of year	$	246.4	$	512.8

Summary of fair and carrying value of debt instruments

The fair values of our debt instruments, which are Level 2 liabilities, are summarized as follows:

	Fair Value As of December 31,
(In millions)	2025		2024
Current portion:
4.050% Senior Notes due September 15, 2025(1)	$	—	$	1,741.0
Current portion of notes payable	—		1,741.0
Non-current portion:
2.250% Senior Notes due May 1, 2030	1,378.7		1,295.6
5.050% Senior Notes due January 15, 2031(1)	413.0		—
5.750% Senior Notes due May 15, 2035(1)	684.5		—
5.200% Senior Notes due September 15, 2045	1,029.5		1,008.0
3.150% Senior Notes due May 1, 2050	973.0		943.7
3.250% Senior Notes due February 15, 2051	461.8		448.9
6.450% Senior Notes due May 15, 2055(1)	737.6		—
Non-current portion of notes payable	5,678.1		3,696.2
Total notes payable	$	5,678.1	$	5,437.2

(1) In May 2025 we issued our 2025 Senior Notes for an aggregate principal amount of $1.75 billion. In June 2025 we used the net proceeds from the sale of our 2025 Senior Notes to redeem in full our 4.050% Senior Notes due September 15, 2025, prior to maturity. For additional information, please read Note 13, Indebtedness, to these consolidated financial statements.