Segment Information - Schedule of Significant Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Research and development	$ 1,631.6	$ 1,421.7	$ 3,175.1	$ 2,749.1
Reportable Segment
Segment Reporting [Line Items]
Research and development	1,631.6	1,421.7	3,175.1	2,749.1
Reimbursement of research and development expenses by collaborators	(26.2)	(42.3)	(59.8)	(79.7)
Reportable Segment \| Clinical manufacturing costs
Segment Reporting [Line Items]
Research and development	404.7	337.0	768.9	647.3
Reportable Segment \| Direct research and development expenses
Segment Reporting [Line Items]
Research and development	539.2	454.1	1,037.8	842.5
Reportable Segment \| Indirect research and development expenses:
Segment Reporting [Line Items]
Research and development	713.9	672.9	1,428.2	1,339.0
Reportable Segment \| Indirect research and development expenses: \| Payroll and benefits
Segment Reporting [Line Items]
Research and development	460.4	449.4	944.5	901.1
Reportable Segment \| Indirect research and development expenses: \| Lab supplies and other research and development costs
Segment Reporting [Line Items]
Research and development	71.5	64.9	130.8	124.9
Reportable Segment \| Indirect research and development expenses: \| Occupancy and other operating costs
Segment Reporting [Line Items]
Research and development	$ 182.0	$ 158.6	$ 352.9	$ 313.0