Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenues	$ 3,675.6	$ 3,547.1	$ 6,704.3	$ 6,692.1
Net product sales
Disaggregation of Revenue [Line Items]
Revenues	1,631.0	1,918.6	3,046.6	3,679.9
Libtayo
Disaggregation of Revenue [Line Items]
Revenues	376.5	297.4	661.6	561.3
U.S. \| ELYEA HD And EYLEA
Disaggregation of Revenue [Line Items]
Revenues	1,147.5	1,534.7	2,190.3	2,936.3
U.S. \| ELYEA HD
Disaggregation of Revenue [Line Items]
Revenues	393.2	304.2	700.0	504.2
U.S. \| EYLEA
Disaggregation of Revenue [Line Items]
Revenues	754.3	1,230.5	1,490.3	2,432.1
U.S. \| Libtayo
Disaggregation of Revenue [Line Items]
Revenues	247.8	182.4	440.3	341.6
U.S. \| Praluent
Disaggregation of Revenue [Line Items]
Revenues	65.8	56.1	122.6	126.1
U.S. \| Evkeeza
Disaggregation of Revenue [Line Items]
Revenues	41.2	30.4	72.1	55.2
Rest Of World \| Libtayo
Disaggregation of Revenue [Line Items]
Revenues	128.7	115.0	221.3	219.7
Rest Of World \| Inmazeb
Disaggregation of Revenue [Line Items]
Revenues	$ 0.0	$ 0.0	$ 0.0	$ 1.0