Collaboration and License Agreement - Additional Information (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2017 USD ($) CandidateorProduct	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Apr. 01, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 01, 2019 USD ($)	Jan. 01, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement revenue recognized		$ 567,000	$ 441,000	$ 1,722,000	$ 1,103,000
Novartis
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront, nonrefundable payment received	$ 35,000,000.0
Allocated to collaboration agreement	33,300,000
Collaborative agreement target fee	$ 5,000,000.0
Collaboration agreement, research term	5 years
Novartis | Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement revenue recognized		600,000	$ 400,000	1,700,000	$ 1,100,000
Deferred revenue		30,400,000		30,400,000		$ 200,000	$ 600,000	$ 31,000,000.0	$ 200,000	$ 400,000
Novartis | Collaborative Arrangement | Reimbursable Research and Development Costs
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable		$ 400,000		400,000				$ 400,000
Novartis | ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price				$ 33,300,000
Novartis | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement, reimbursement of manufacturing activities during research term	$ 17,000,000.0
Collaboration agreement number of candidates or products for develop and commercialize | CandidateorProduct	1
Collaboration agreement eligible milestone payments eligible to receive	$ 265,000,000.0
Collaboration agreement eligible development milestone payments eligible to receive	90,000,000.0
Collaboration agreement eligible regulatory milestone payments eligible to receive	85,000,000.0
Collaboration agreement eligible commercial milestone payments eligible to receive	90,000,000.0
Novartis | Series B Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront, nonrefundable payment received	1,700,000
Proceeds from issuance of shares of preferred stock	10,000,000.0
Preferred stock estimated fair value	$ 11,700,000