Segment Information - Schedule of Significant Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Research and development	$ 1,421.7	$ 1,200.0	$ 2,749.1	$ 2,448.4
Reportable Segment
Segment Reporting Information [Line Items]
Research and development	1,421.7	1,200.0	2,749.1	2,448.4
Reimbursement of research and development expenses by collaborators	(42.3)	(44.6)	(79.7)	(88.4)
Reportable Segment \| Clinical manufacturing costs
Segment Reporting Information [Line Items]
Research and development	337.0	260.1	647.3	534.6
Reportable Segment \| Direct research and development expenses
Segment Reporting Information [Line Items]
Research and development	454.1	363.9	842.5	772.3
Reportable Segment \| Indirect research and development expenses:
Segment Reporting Information [Line Items]
Research and development	672.9	620.6	1,339.0	1,229.9
Reportable Segment \| Indirect research and development expenses: \| Payroll and benefits
Segment Reporting Information [Line Items]
Research and development	449.4	422.5	901.1	841.4
Reportable Segment \| Indirect research and development expenses: \| Lab supplies and other research and development costs
Segment Reporting Information [Line Items]
Research and development	64.9	56.5	124.9	112.4
Reportable Segment \| Indirect research and development expenses: \| Occupancy and other operating costs
Segment Reporting Information [Line Items]
Research and development	$ 158.6	$ 141.6	$ 313.0	$ 276.1