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Acquisitions, Research Collaborations and Licensing Agreements - Narrative (Details) $ in Millions	1 Months Ended						3 Months Ended			9 Months Ended		15 Months Ended
	Oct. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)	Jul. 31, 2024 USD ($) aqua_facility	Mar. 31, 2024 USD ($)	Dec. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	May 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Feb. 29, 2024 USD ($)
Business Combination [Line Items]
Research and development								$ 4,234.0	$ 5,862.0	$ 11,903.0	$ 13,354.0
Property, plant and equipment, net		$ 25,639.0						25,639.0		25,639.0		$ 25,639.0		$ 23,779.0
Intangible assets		15,313.0						15,313.0		15,313.0		15,313.0		$ 16,370.0
Elanco Animal Health Incorporated Aqua Business
Business Combination [Line Items]
Cash paid for acquisition of business					$ 1,300.0
Aqua manufacturing facilities | aqua_facility					2,000,000
Verona Pharma plc | Subsequent Event
Business Combination [Line Items]
Consideration transferred, asset acquisition	$ 10,500.0
LaNova Medicines Ltd
Business Combination [Line Items]
Research and development								300.0		300.0
HRS-5346 , Jiangsu Hengrui Pharmaceuticals Co., Ltd.
Business Combination [Line Items]
Research and development										200.0
Jiangsu Hengrui Pharmaceuticals Co., Ltd.
Business Combination [Line Items]
Future contingent developmental milestone payments (up to)													$ 92.5
Future regulatory milestone payments (up to)													177.5
Maximum aggregate sales-based milestone payments													$ 1,500.0
WuXi Vaccines' facility
Business Combination [Line Items]
Consideration transferred, asset acquisition			$ 437.0
WuXi Vaccines' facility | Asset under Construction
Business Combination [Line Items]
Property, plant and equipment, net			$ 759.0
MK-1045/CN201, Curon Biopharmaceutical
Business Combination [Line Items]
Research and development									750.0		750.0
Consideration transferred, asset acquisition				$ 700.0
Future contingent developmental milestone payments (up to)				300.0					300.0		300.0
Future regulatory milestone payments (up to)				300.0					300.0		300.0
Eyebiotech Limited
Business Combination [Line Items]
Research and development									1,350.0		1,350.0
Consideration transferred, asset acquisition					$ 1,200.0
Future contingent developmental milestone payments (up to)					1,000.0
Future regulatory milestone payments (up to)					200.0
Maximum aggregate sales-based milestone payments					500.0
Asset acquisition, transaction costs					207.0
Developmental milestone payment triggered and paid									100.0	100.0	100.0	200.0
Net assets acquired					$ 21.0
Harpoon Therapeutics, Inc.
Business Combination [Line Items]
Research and development											656.0
Consideration transferred, asset acquisition						$ 765.0
Asset acquisition, transaction costs						$ 56.0
Net assets acquired											165.0
Forecast | sac-TMT
Business Combination [Line Items]
Research and development arrangement, contract to perform for others, compensation earned	700.0
Dr. Falk Pharma | Forecast
Business Combination [Line Items]
Research and development							$ 150.0
Third-Party | MK-1045/CN201, Curon Biopharmaceutical
Business Combination [Line Items]
Net assets acquired				$ 128.0					$ 128.0		$ 128.0
Alteogen Inc.
Business Combination [Line Items]
Aggregate, regulatory milestones payments, maximum															$ 51.0
Sales milestone payments															$ 1,000.0
Sales based royalty percentage															2.00%
Collaborative arrangement, rights and obligations, probable contingent payments		680.0
Alteogen Inc. | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Keytruda Qlex
Business Combination [Line Items]
Liabilities resulting milestone payments		705.0						705.0		705.0		705.0
Intangible assets		$ 705.0						$ 705.0		$ 705.0		$ 705.0
Alteogen Inc. | Subsequent Event | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Keytruda Qlex
Business Combination [Line Items]
Liabilities resulting milestone payments	$ 25.0

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