Collaborations - Additional Information (Details)						3 Months Ended		9 Months Ended
	Aug. 20, 2020	Jul. 07, 2020 USD ($)	May 09, 2019 USD ($) $ / shares shares	Nov. 01, 2018	Oct. 31, 2017 shares	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized						$ 14,533,000	$ 950,000	$ 21,249,000	$ 1,101,000
Stock split, conversion ratio	1.5949
Research and development						15,778,000	11,310,000	41,713,000	26,072,000
Sanofi Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment		$ 150,000,000
Collaboration agreement transaction price		150,000,000
Revenue recognized recorded in deferred revenue						10,900,000		10,900,000
Unsatisfied performance obligation						139,700,000		139,700,000
Sanofi Agreement | Collaboration Target 1
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price		120,000,000
Revenue recognized recorded in deferred revenue						10,200,000		10,200,000
Sanofi Agreement | Collaboration Target 2
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price		30,000,000
Revenue recognized recorded in deferred revenue						700,000		700,000
Sanofi Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payments		1,480,000,000
Commercial Milestone Payments		700,000,000
Sanofi Agreement | Minimum | IRAK4 Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payments		1,000,000,000
Commercial Milestone Payments		$ 400,000,000
Vertex Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized recorded in deferred revenue								10,300,000
Unsatisfied performance obligation						42,600,000		42,600,000		$ 53,000,000
Initial research term of collaboration			4 years
Extended research term of collaboration			1 year
Revenue recognized						$ 3,600,000	$ 1,000,000	$ 10,300,000	1,100,000
Vertex Agreement | Series B-1 Convertible Preferred
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price			$ 55,900,000
Non refundable upfront payment received			$ 50,000,000
Number of shares issued | shares			3,059,695
Stock issued price per share | $ / shares			$ 6.54
Preferred stock premium			$ 5,900,000
Vertex Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue remaining research term						2 years 7 months 6 days		2 years 7 months 6 days
Eligible to receive payments including development, regulatory and commercial milestones			$ 170,000,000
Compound Collaboration
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period to terminate collaboration agreement								60 days
Compound Collaboration | Series A Preferred Units
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of shares issued | shares					886,305
Stock split, conversion ratio				100
Share-based compensation vesting period				3 years
Research and development								$ 300,000	$ 300,000
Number of shares vested | shares								166,183	166,183