Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended			12 Months Ended
	Oct. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Oct. 31, 2018 Suite	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) Suite	Dec. 31, 2019 USD ($)	Jun. 30, 2018 mo
CRO [Member]
Commitments And Contingencies [Line Items]
Cancellable future commitments				$ 378.5
CRO [Member] | Other Funding Commitments [Member]
Commitments And Contingencies [Line Items]
Expenditures incurred by CROs				$ 47.9	$ 40.4	$ 31.6
Supply Agreement [Member] | Thermo Fisher Scientific, Inc. [Member]
Commitments And Contingencies [Line Items]
Number of dedicated clean room suites | mo							4
Agreement expiration date			Dec. 31, 2028
Supply Agreement [Member] | Thermo Fisher Scientific, Inc. [Member] | Research and Development Expense [Member]
Commitments And Contingencies [Line Items]
Derecognition of right of use asset	$ 23.4
Derecognition of lease liabilities	20.1
Recognition of loss	3.3
Non refundable advance payments	$ 21.1
Catalent Agreements [Member] | Research and Development Expense [Member]
Commitments And Contingencies [Line Items]
Derecognition of right of use asset		$ 22.8
Derecognition of lease liabilities		20.0
Recognition of loss		$ 2.8
Catalent Agreements [Member] | Paragon [Member]
Commitments And Contingencies [Line Items]
Number of dedicated clean room suites | Suite			2		4
Number of additional clean room suites available on optional reserve | Suite			2
Agreement expiration date			Dec. 31, 2024
Clinical and Commercial Supply Agreement [Member] | Aldevron LLC [Member]
Commitments And Contingencies [Line Items]
Agreement expiration date				Dec. 31, 2026
Agreement expiration description				The Company has the option to extend the term of the Aldevron Agreements by one year if the Company delivers a written notice of its intention to extend to Aldevron no later than June 1, 2025. Both parties have the right to early terminate without additional penalty. The Company has determined that the Aldevron Agreements do not contain an embedded lease because it does not convey the right to control the use of Aldevron’s facility or related equipment therein.