Collaboration and License Agreements (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($) geneTherapyProgram $ / shares shares	Jun. 30, 2024 USD ($) non-clinicalStageCompound	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) preclinicalCandidate undisclosedProgram $ / shares shares	Dec. 31, 2023 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Acquired in-process research and development	$ 2.5		$ 0.0		$ 8.5	$ 143.9
Unrealized (loss) gain on equity securities	(19.9)		37.3		(18.3)	39.5
Equity security investments	143.6				143.6					$ 161.9
Total revenues	590.2		452.7		1,105.5	873.1
Collaborative Arrangement | Common Stock | Voyager
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Beneficial ownership (as a percent)				19.90%
Nxera | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	2,600.0				$ 2,600.0
Research and development	15.0
Agreement termination, minimal contractual time (in days)					180 days
Agreement termination, contractual time threshold (in days)					90 days
Agreement termination by counterparty, contractual time threshold (in days)					365 days
Agreement termination by counterparty, minimal contractual time (in days)					120 days
Takeda | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	1,900.0				$ 1,900.0
Research and development	7.5
Agreement termination, minimal contractual time (in days)					6 months
Agreement termination, contractual time threshold (in days)					12 months
Number of non-clinical stage compounds | non-clinicalStageCompound					3
Idorsia | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	1,700.0				$ 1,700.0
Agreement termination, minimal contractual time (in days)					90 days
Agreement termination, due to material breach (in days)					90 days
Xenon | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	1,700.0				$ 1,700.0
Agreement termination, contractual time threshold (in days)					90 days
Number of preclinical candidates | preclinicalCandidate									3
Share price (in USD per share) | $ / shares							$ 31.855	$ 19.9755	$ 14.196
Equity securities fair value (Level 3)								$ 4.6	$ 14.1
Equity securities fair value (Level 1)							$ 7.7
Xenon | Collaborative Arrangement | Common Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock (in shares) | shares							0.3	0.3	1.4
Voyager | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Unrealized (loss) gain on equity securities	(12.0)		32.1		$ (4.5)	41.3
Equity security investments	67.8				67.8
Voyager | Collaborative Arrangement | Common Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock (in shares) | shares				4.4					4.2
Transfer, beneficial ownership, and voting restrictions period				3 years
2019 Voyager Agreement | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	1,300.0				$ 1,300.0
Research and development		$ 5.0
Agreement termination, minimal contractual time (in days)					180 days
Agreement termination, contractual time threshold (in days)					1 year
Share price (in USD per share) | $ / shares									$ 11.9625
Equity securities fair value (Level 3)									$ 54.7
Number of undisclosed programs | undisclosedProgram									2
2023 Voyager Agreement | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments	6,100.0				$ 6,100.0
Research and development	3.0
Agreement termination, minimal contractual time (in days)					180 days
Agreement termination, contractual time threshold (in days)					1 year
Share price (in USD per share) | $ / shares				$ 8.88
Equity securities fair value (Level 1)				$ 31.3
Number of gene therapy programs | geneTherapyProgram				3
Upfront payment				$ 175.0
Board of directors maximum duration term (in years)				10 years
Acquired in-process research and development				$ 143.9
MTPC | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Agreement termination, contractual time threshold (in days)					180 days
Potential milestone payment receipts	30.0				$ 30.0
MTPC | Collaborative Arrangement | Minimum | Patents
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Patent term (in years)					10 years
AbbVie | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Agreement termination, contractual time threshold (in days)					180 days
Potential milestone payment receipts	366.0				$ 366.0
AbbVie | Collaborative Arrangement | Royalty
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ 3.5		$ 4.2		$ 6.5	$ 7.9
AbbVie | Collaborative Arrangement | Minimum | Patents
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Patent term (in years)					10 years