Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Alnylam (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (1,075.3)	$ (911.3)	$ (3,261.8)	$ (2,549.4)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | (R&D expense)
Disaggregation of Revenue [Line Items]
Research and development expenses	(13.5)	(10.6)	(52.1)	(36.1)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Acquired in-process research and development
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (100.0)	$ 0.0	$ (100.0)	$ 0.0