Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Alnylam (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (4,439.0)	$ (3,592.5)	$ (2,860.1)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | (R&D expense)/Reduction of R&D expense
Disaggregation of Revenue [Line Items]
Research and development expenses	(74.1)	(55.8)	(60.5)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Acquired in-process research and development
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (100.0)	$ 0.0	$ 0.0