Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Roche (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 5,138.5	$ 1,952.0	$ 7,667.2	$ 3,780.2
Casirivimab and imdevimab | Roche Collaboration Agreement | Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues	167.9	0.0	234.7	0.0
Casirivimab and imdevimab | Roche Collaboration Agreement | Research and development expense
Disaggregation of Revenue [Line Items]
Reduction of Research and development expense	$ 41.0	$ 0.0	$ 127.8	$ 0.0