Research and Collaboration Arrangements - Roche Agreement - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 162,000	$ 14,580,000	$ 1,382,000	$ 16,580,000
Roche | 2017 Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable upfront payments received	$ 21,000,000.0
Contingent payment for each nominated product beyond the first three	1,000,000.0
Maximum contingent payment upon exercise of the option to convert a product	30,000,000.0
Maximum development milestone payments	223,000,000.0
Development milestone payments relating to Choroideremia	86,000,000.0
Maximum sales-based milestone payments	$ 123,000,000.0
Non-refundable development milestone payments				10,000,000.0
Collaborative arrangement adjustment to transaction price					8,500,000
Revenues		0	$ 14,300,000	0	$ 15,900,000
Deferred revenue		0		0		$ 0
Accounts receivable		0		0		0
Remaining performance obligations		$ 0		$ 0		$ 0