Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Roche (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 2,528.7	$ 1,828.2
Casirivimab and imdevimab | Roche Collaboration Agreement | Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues	66.8	0.0
Casirivimab and imdevimab | Roche Collaboration Agreement | Research and development expense
Disaggregation of Revenue [Line Items]
Reduction of Research and development expense	$ 86.8	$ 0.0