Segment Information - Schedule of Significant Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Research and development	$ 1,543.5	$ 1,327.4
Reportable Segment
Segment Reporting Information [Line Items]
Research and development	1,543.5	1,327.4
Reimbursement of research and development expenses by collaborators	(33.6)	(37.3)
Reportable Segment \| Clinical manufacturing costs
Segment Reporting Information [Line Items]
Research and development	364.1	310.3
Reportable Segment \| Direct research and development expenses
Segment Reporting Information [Line Items]
Research and development	498.6	388.4
Reportable Segment \| Indirect research and development expenses:
Segment Reporting Information [Line Items]
Research and development	714.4	666.0
Reportable Segment \| Indirect research and development expenses: \| Payroll and benefits
Segment Reporting Information [Line Items]
Research and development	484.2	451.6
Reportable Segment \| Indirect research and development expenses: \| Lab supplies and other research and development costs
Segment Reporting Information [Line Items]
Research and development	59.3	60.0
Reportable Segment \| Indirect research and development expenses: \| Occupancy and other operating costs
Segment Reporting Information [Line Items]
Research and development	$ 170.9	$ 154.4