Acquisitions - Intangible assets, Goodwill, Leases and Acquisition-related expense (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2025 USD ($)	Mar. 31, 2025 ft²	Jul. 02, 2024 USD ($)	Sep. 30, 2023 ft²	Sep. 27, 2023 USD ($)	Sep. 26, 2023 USD ($)
Business Combination [Line Items]
Goodwill(1)	$ 6,478.9	$ 6,219.2	$ 6,491.1
Operating lease area | ft²				580,000
Human Immunology Biosciences
Business Combination [Line Items]
Intangible assets:					$ 1,600.0
Goodwill(1)					261.0
Acquisition related costs	$ 2.8
Operating lease liabilities					1.2
Operating lease assets					1.2
Human Immunology Biosciences | Other clinical programs
Business Combination [Line Items]
Intangible assets:					$ 7.9
Human Immunology Biosciences | Risk-adjusted discount rate
Business Combination [Line Items]
Measurement input					0.145
Human Immunology Biosciences | Felzartamab (IgAN)
Business Combination [Line Items]
Intangible assets:					$ 920.0
Human Immunology Biosciences | Felzartamab (IgAN) | In-process research and development (omaveloxolone)
Business Combination [Line Items]
Intangible assets:					920.0
Human Immunology Biosciences | Felzartamab (AMR)
Business Combination [Line Items]
Intangible assets:					450.0
Human Immunology Biosciences | Felzartamab (AMR) | In-process research and development (omaveloxolone)
Business Combination [Line Items]
Intangible assets:					450.0
Human Immunology Biosciences | Felzartamab (PMN)
Business Combination [Line Items]
Intangible assets:					265.0
Human Immunology Biosciences | Felzartamab (PMN) | In-process research and development (omaveloxolone)
Business Combination [Line Items]
Intangible assets:					$ 265.0
Reata Pharmaceuticals, Inc
Business Combination [Line Items]
Goodwill(1)			469.2				$ 469.2
Separately recognized transactions, additional disclosures, acquisition cost expensed		$ 28.4
Fair value indefinite lived intangible assets discount rate								14.30%
Operating lease area | ft²						327,400
Operating lease, contract term						16 years
Operating lease liabilities			151.8				151.8
Remaining lease term								15 years
Operating lease assets			121.2				121.2
Business Combination, Separately Recognized Transaction, Acquisition-Related Cost, Expensed, Statement of Income or Comprehensive Income [Extensible Enumeration]		Selling, general and administrative
Reata Pharmaceuticals, Inc | Completed technology for SKYCLARYS (U.S.)
Business Combination [Line Items]
Intangible assets:			4,200.0				4,200.0	$ 4,200.0
Reata Pharmaceuticals, Inc | In-process research and development (omaveloxolone)
Business Combination [Line Items]
Intangible assets:			2,300.0				2,300.0
Reata Pharmaceuticals, Inc | Priority review voucher
Business Combination [Line Items]
Intangible assets:			100.0					$ 100.0
Reata Pharmaceuticals, Inc | Other clinical programs
Business Combination [Line Items]
Intangible assets:			$ 40.0				$ 40.0