Segment Information - Schedule of Significant Segment Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Total revenues	$ 2,770.2	$ 2,690.6
Cost of sales	363.0	342.6
Acquired in-process research and development expenses	19.8	76.8
Intangible asset impairment charge	379.0	0.0
Interest income	(120.9)	(181.2)
Provision for income taxes	84.1	179.5
Net income	646.3	1,099.6
Pharmaceuticals
Segment Reporting Information [Line Items]
Total revenues	2,770.2	2,690.6
Research expenses	206.1	196.1
Development expenses	773.6	593.0
Acquired in-process research and development expenses	19.8	76.8
Selling and other commercial expenses	241.1	191.7
General and administrative expenses	155.3	151.0
Intangible asset impairment charge	379.0	0.0
Interest income	(120.9)	(181.2)
Other segment items	22.8	41.5
Provision for income taxes	84.1	179.5
Net income	646.3	1,099.6
Products
Segment Reporting Information [Line Items]
Total revenues	2,760.2	2,690.6
Products | Pharmaceuticals
Segment Reporting Information [Line Items]
Cost of sales	130.6	108.8
Royalty | Pharmaceuticals
Segment Reporting Information [Line Items]
Cost of sales	$ 232.4	$ 233.8