Collaborations - Additional Information (Detail) - USD ($)		1 Months Ended			3 Months Ended		6 Months Ended
	May 08, 2020	Jun. 30, 2022	Jan. 31, 2020	Dec. 31, 2018	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Research and development					$ 1,871,000	$ 15,389,000	$ 11,574,000	$ 32,402,000
Deferred revenue, recognized							200,000
Mosaic Biosciences Inc | Maximum
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Milestone payment related to regulatory and clinical development events	$ 4,000,000.0
ISU Abxis | Amended and Restated License Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Regulatory and development milestone payment				$ 2,500,000			0
ISU Abxis | Maximum | Amended and Restated License Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Milestone payment				19,500,000			0
Commercial milestone payments				$ 17,000,000.0			0
Biogen | Collaboration
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Research and development						$ 1,100,000	700,000	$ 2,600,000
Biogen | Exclusive License
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Up-front payments received			$ 15,000,000.0
Biogen | Termination Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Forgiveness of accounts receivable, net		$ 600,000			600,000		$ 600,000
Payments to cash		$ 10,000
Biogen | Termination Agreement | General and Administrative
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Settlement expense					$ 600,000
Biogen | Maximum | Exclusive License
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Development and sales milestone payments			$ 340,000,000.0