Collaboration and License Agreements - Additional Information (Details)		1 Months Ended		3 Months Ended
	Dec. 22, 2018 USD ($) Target	May 31, 2021 USD ($)	Dec. 31, 2018 USD ($) Target Protein	Mar. 31, 2021 USD ($) Target Performanceobligation TargetProtein
Restated Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of potential targets | Target	6
Additional upfront consideration received	$ 40,000,000
Annual research plan payments receivables	$ 1,000,000
Annual research plan payments periods	3 years
Collaboration description				The Company has control over the committee and may terminate the Roche Agreement on a target-by-target or product-by-product basis under several scenarios, upon at least 90 days’ prior written notice.
Restated Roche Agreement | Lead Series Identification Achievement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees	$ 2,000,000
Restated Roche Agreement | Good Laboratory Practice (“GLP”) Toxicology (“Tox”) Study Phase
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees	3,000,000
Restated Roche Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees	20,000,000
Restated Roche Agreement | Maximum | Research, Development and Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	275,000,000
Restated Roche Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	150,000,000
Restated Roche Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees	$ 7,000,000
Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date			2018-12
Research agreement, period			54 months
Additional payment on extension of contract			$ 62,500,000
Nonrefundable upfront payment				$ 45,000,000
Number of performance obligation | Performanceobligation				1
Number of targets | Target				5
Number of additional targets | Target				2
Biogen License Agreement | Scenario Forecast
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Lead initiation fee achieved		$ 3,000,000
Biogen License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targeted protein degradation | Protein			5
Additional targets for development | Target			5
Biogen License Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 26,000,000
Biogen License Agreement | Maximum | Research And Development Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 35,000,000
Biogen License Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement				90 days
Calico License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligation | Performanceobligation				1
Number of targets | Target				5
Research term				5 years
Upfront payment				$ 5,000,000
Annual Payments				$ 5,000,000
Contractual term				5 years
Calico License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of target proteins | TargetProtein				5
Calico License Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 65,000,000
Calico License Agreement | Maximum | Potential Research, Development and Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 132,000,000