Collaboration Agreements - Summary of Activity and Reimbursement Amounts Related to Collaboration Agreement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	$ 8,654	$ 2,474	$ 16,556	$ 5,768
Research and development expenses	62,564	97,161	134,297	189,987
Selling, general and administrative expenses	55,983	75,565	108,556	141,273
Collaboration Revenue - Related Party [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	7,420		13,633
Biogen Collaboration Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						$ 1,100,000
Cost of revenues	1,294		2,495
Research and development expenses	4,943	27,679	11,974	49,851
Selling, general and administrative expenses	13,072	28,755	26,055	47,718
Reimbursement amounts to (from) collaboration [Abstract]
Collaboration revenue - related party	(7,420)		(13,633)		$ 8,000
Cost of revenues	(566)		(1,128)
Selling, general and administrative expenses	1,019	7,476	3,325	10,510
Biogen Collaboration Agreement [Member] | Research and Development [Member]
Reimbursement amounts to (from) collaboration [Abstract]
Research and development expenses	(3,325)	$ (22,418)	(8,982)	$ (39,700)
Biogen Collaboration Agreement [Member] | Collaboration Revenue - Related Party [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	$ 7,420		$ 13,633