Collaborations and Other Arrangements - Additional Information (Detail)		1 Months Ended			3 Months Ended	12 Months Ended
	May 30, 2020 USD ($) $ / shares shares	Oct. 31, 2023 USD ($)	May 31, 2020 Product Targetcap	Apr. 30, 2016 USD ($)	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Costs to obtain or fulfill contract capitalized					$ 0	$ 0
Common stock, par value | $ / shares					$ 0.0001	$ 0.0001	$ 0.0001
Collaboration revenue						$ 36,275,000	$ 52,121,000	$ 33,053,000
Deferred revenue					$ 60,993,000	60,993,000	63,771,000	127,235,000
Revenue						6,600,000	11,400,000	2,900,000
Regeneron Pharmaceuticals Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Extension fee						30,000,000
Stock purchase agreement date	May 30, 2020
Transaction price						51,700,000
Remaining transaction price transferred at inception of arrangement						11,400,000
Transaction price allocated to combined performance obligation						51,700,000
Aggregate transaction price remaining to be recognized					47,100,000	47,100,000
Deferred revenue					47,100,000	47,100,000	28,800,000
Regeneron Pharmaceuticals Inc. [Member] | Hemophilia Co Co Agreements
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						10,700,000	10,400,000	2,700,000
Regeneron Pharmaceuticals Inc. [Member] | 2016 Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions						75,000,000
Regeneron Pharmaceuticals Inc. [Member] | 2016 Regeneron Agreement [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments				$ 25,000,000
Regulatory based milestone payments under agreement				110,000,000
Sales based milestone payments under agreement				185,000,000
Regeneron Pharmaceuticals Inc. [Member] | Stock Purchase Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase of common stock through private placement				$ 50,000,000
Regeneron Pharmaceuticals Inc. [Member] | 2020 Regeneron Amendment [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions	$ 70,000,000
Fee to extend collaboration arrangement	$ 25,000,000
Collaboration term extension period	2024-04
Regeneron Pharmaceuticals Inc. [Member] | 2020 Stock Purchase Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Common stock shares sold | shares	925,218
Common stock, par value | $ / shares	$ 0.0001
Cash consideration received on sale of common stock	$ 30,000,000
Sale of stock, price per share | $ / shares	$ 32.42
Percentage of premium over volume-weighted average trading price of common stock during 30-day period prior to closing of equity transaction	100.00%
Regeneron Pharmaceuticals Inc. [Member] | 2024 Technology Collaboration Extension [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount allocated to licenses to targets and associated research activities and evaluation plans						48,300,000
Amount allocated to technology collaboration and associated research activities						3,400,000
Cumulative catch up adjustment					10,300,000	10,300,000
Regeneron Pharmaceuticals Inc. [Member] | Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement further option extension period		two years
Additional regeneron target cap | Targetcap			5
Number of unique ex vivo products commercialized | Product			10
Collaboration term extension period		2026-04
Collaboration revenue						21,000,000	24,100,000	25,700,000
Payments due						19,600,000	11,900,000	5,900,000
Deferred revenue		$ 30,000,000
Regeneron Pharmaceuticals Inc. [Member] | Related Party [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					35,700,000	35,700,000	3,200,000
ONK Therapeutics [Member] | Research Materials Shippmet Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						200,000	100,000
ONK Therapeutics [Member] | Related Party [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					0	0	100,000
Kyverna [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue					0	0	400,000
Revenue						400,000	6,600,000	0
Kyverna [Member] | Research Materials Shippmet Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue						100,000
Kyverna [Member] | Related Party [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					100,000	100,000	0
Sparing Vision [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						1,800,000	200,000	0
Deferred revenue					13,900,000	13,900,000	14,700,000
Sparing Vision [Member] | Related Party [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					500,000	500,000	100,000
AvenCell Member
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions						6,600,000	11,400,000	2,900,000
Collaboration revenue						13,200,000	22,800,000	5,900,000
Deferred revenue					0	0	19,900,000
AvenCell Member | Research Materials Shippmet Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						200,000	300,000
AvenCell Member | AvenCell Co/Co Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						600,000	2,000,000	$ 200,000
AvenCell Member | Related Party [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable					$ 200,000	$ 200,000	$ 300,000