Collaborations and Other Arrangements - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	78 Months Ended
	Feb. 12, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Sep. 30, 2022	Dec. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Capitalized Contract Cost, Gross			$ 0		$ 0			$ 0
Collaboration revenue			13,266,000	$ 7,204,000	38,548,000	$ 20,199,000
Accounts receivable							$ 0
Deferred revenue		$ 119,782,000	80,496,000	119,782,000	80,496,000	119,782,000	127,235,000	80,496,000	$ 73,931,000
Revenue			2,900,000		8,500,000
Regeneron Pharmaceuticals Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate transaction price remaining to be recognized			34,500,000		34,500,000			34,500,000
Accounts receivable			4,000,000.0		4,000,000.0		2,000,000.0	4,000,000.0
Deferred revenue			34,500,000		34,500,000		51,400,000	34,500,000
Regeneron Pharmaceuticals Inc. [Member] | Hemophilia Co Co Agreements
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue			3,200,000	1,100,000	6,900,000	2,100,000
Regeneron Pharmaceuticals Inc. [Member] | Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions								145,000,000.0
Collaboration revenue			6,500,000	6,700,000	$ 18,600,000	18,700,000		167,600,000
Aggregate transaction price remaining to be recognized, period					Through September 30, 2022
Payments due			4,000,000.0	2,100,000	$ 8,700	3,900,000
Regeneron Pharmaceuticals Inc. [Member] | Regeneron Agreement [Member] | Research and Development Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue								39,700,000
Novartis [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue		$ 300,000
Strategic collaboration agreement amended date					2018-12
One time payment to novartis							10,000,000.0
Novartis [Member] | AvenCell Co Co Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue			0		$ 0		0	0
ONK Therapeutics [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development And Commercial Milestone Payment To be Received	$ 184,000,000
Kyverna Therapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable			0		0		0	0
Deferred revenue			2,700,000		2,700,000		7,000,000.0	2,700,000
Revenue			2,300,000		4,300,000
Sparing Vision [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue			0	0	0	0
Accounts receivable			0		0			0
Deferred revenue			14,800,000		14,800,000		14,800,000	14,800,000
AvenCell [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions			2,900,000	62,500	8,500,000	62,500
Collaboration revenue			5,700,000	125,000.0	17,100,000	125,000.0
Accounts receivable			0		0			0
Deferred revenue			28,500,000		28,500,000		54,100,000	$ 28,500,000
AvenCell [Member] | AvenCell Co Co Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue			$ 1,300,000	$ 200,000	$ 1,400,000	$ 200,000
Accounts receivable							$ 100,000