Collaboration and Licensing Agreements (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2018 USD ($) item	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Gilead Collaboration and License Agreement
Collaboration and Licensing Agreements
Number of preclinical research programs | item	2
Upfront payment received	$ 10.0
Program initiation fee	$ 15.0
Payment term (in days)	60 days
Milestone payment received	$ 8.0
Upfront and milestone payments included in deferred revenues		$ 13.9		$ 13.9		$ 4.3
Percentage of upfront payment included in deferred revenue expected to be recognized in 2022		6.00%		6.00%
Percentage of upfront payment included in deferred revenue expected to be recognized in 2023		59.00%		59.00%
Percentage of upfront payment included in deferred revenue expected to be recognized in 2024		23.00%		23.00%
Percentage of upfront payment included in deferred revenue expected to be recognized in 2025		12.00%		12.00%
Cost reimbursements for research and development services included in deferred revenues		$ 0.4		$ 0.4		1.2
Revenue recognized from milestone payments		1.3	$ 0.2	2.9	$ 1.9
Revenue recognized from cost reimbursements for research and development services		0.9	3.7	3.5	12.7
Revenue recognized from cost reimbursements for research and development services initially recorded as deferred revenue		0.1	$ 1.0	0.7	$ 1.6
Contract asset relating to the sublicense payment		$ 0.2		$ 0.2		$ 0.3
Development Milestones | HBV program
Collaboration and Licensing Agreements
Total milestone amount	140.0
Development Milestones | HIV program
Collaboration and Licensing Agreements
Option exercise payment	10.0
Development Milestones | HIV program | Maximum
Collaboration and Licensing Agreements
Total milestone amount	172.5
Commercial Milestones | HBV program
Collaboration and Licensing Agreements
Total milestone amount	50.0
Commercial Milestones | HIV program
Collaboration and Licensing Agreements
Total milestone amount	$ 65.0