Significant Agreements - Novartis Option and License Agreement & Stock Purchase Agreement (Details) $ in Thousands				1 Months Ended				12 Months Ended
	Mar. 04, 2024 item	Mar. 01, 2023 item	Mar. 04, 2022 USD ($) item	Oct. 31, 2024 USD ($)	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Apr. 30, 2023 USD ($)	Dec. 31, 2024 USD ($) item	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 28, 2023 USD ($) shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue								$ 80,001	$ 250,008	$ 40,907
Contract with customer liability revenue recognized								0	0	$ 40,000
Contract with Customer, Asset, Net, Current						$ 3,341		676	3,341
Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations | item			3
Number of material rights | item			3
Novartis agreement 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment			$ 54,000
Novartis Pharma, AG | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment								80,000
Shares of common stock | shares											2,145,002
Aggregate purchase price											$ 20,000
Amount of premium					$ 700
Allocation of fixed consideration								80,000
Costs to obtain collaboration agreement						1,900			1,900
Contract expense									1,900
Contract with customer liability revenue recognized						80,000		4,200
Accounts receivable related to reimbursable costs								1,500
Novartis Pharma, AG | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue				$ 15,000				15,000
Number of transgenes | item	3
Number of novartis target prior not elected license | item			1
Number of additional targets | item		2	2
Upfront payment			$ 54,000					15,000
Number of options | item			1
Number of material rights | item			3
Allocation of transaction price			$ 18,000			25,000			25,000
Contract with customer liability revenue recognized								15,000	79,000
Option exercise							$ 25,000
Novartis Pharma, AG | First and Second Material Right
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of transaction price						$ 54,000			$ 54,000
Novartis Pharma, AG | Sales milestone | 2023 Novartis Collaboration Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of variable consideration								775,000
Novartis Pharma, AG | Sales milestone | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner			175,000
Novartis Pharma, AG | Development milestone | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of variable consideration								425,000
Novartis Pharma, AG | License option exercise | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner			125,000
Novartis Pharma, AG | Direct licensed product | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner			$ 130,000
Novartis Pharma, AG | SMA Program | Development, regulatory and commercialization milestone | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								200,000
Novartis Pharma, AG | SMA Program | Sales milestone | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								400,000
Novartis Pharma, AG | HD Program | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocation of variable consideration								24,200
Novartis Pharma, AG | HD Program | Development, regulatory and commercialization milestone | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								225,000
Novartis Pharma, AG | HD Program | Sales milestone | 2023 Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								$ 375,000
Novartis Pharma, AG | Discovery Programs 2023 | 2023 Novartis Collaboration Agreement | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of options | item								4
Novartis Pharma, AG | Direct licensed product | Development, regulatory and commercialization milestone | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								$ 130,000
Novartis Pharma, AG | Direct licensed product | Sales milestone | Option and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate maximum milestone payments to be received from collaborative partner								$ 175,000