Collaboration, License and Research Agreements - Additional Information (Details)	1 Months Ended		12 Months Ended
	Nov. 30, 2019 shares	Apr. 30, 2019 USD ($) Product	Dec. 31, 2021 USD ($) Obligation	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized			$ 9,326,000	$ 6,787,000	$ 2,319,000
Lilly Note | Series C Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Conversion of convertible note payable to preferred stock | shares	4,576,342
Research Collaboration and License Agreement with Eli Lilly
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees received		$ 20,000,000.0
License agreement expiry period		10 years
Number of performance obligation | Obligation			1
Period for expects performance obligation			5 years
Revenue recognized			$ 9,100,000	6,800,000	2,300,000
Deferred revenue			11,108,000	15,840,000	$ 18,940,000
Research Collaboration and License Agreement with Eli Lilly | Prepaid and Other Assets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration receivables			900,000	1,200,000
Research Collaboration and License Agreement with Eli Lilly | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Rights to antibody oligonucleotide conjugates for messengers RNA targets. | Product		6
Development milestone payment eligible to receive per target		$ 60,000,000.0
Regulatory milestone payment eligible to receive per target		140,000,000.0
Commercialization milestone payment eligible to receive		$ 205,000,000.0
Research Collaboration with MyoKardia, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized			$ 200,000	$ 0