Research Collaboration and License Agreements - Additional Information (Details)	1 Months Ended	4 Months Ended	9 Months Ended		12 Months Ended
	Nov. 30, 2017 USD ($) Target	Dec. 31, 2015 USD ($)	Sep. 30, 2020 USD ($) Contract	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)
Research Collaboration And License Agreements [Line Items]
Account receivable			$ 2,444,450
Revenue recognized on research collaboration and license agreements			19,500,000
Changes in deferred revenue due to additions to deferred revenue			(13,102,948)	$ 8,513,945
Unsatisfied performance obligations expected to be recognized as revenue			45,300,000
Bayer Collaboration Agreement
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised									$ 17,500,000
Bayer Collaboration Agreement | Research Funding Payments
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised							$ 3,000,000.0		1,500,000
Bayer Collaboration Agreement | Research Funding Payments | Scenario Forecast
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised						$ 10,500,000
Bayer Collaboration Agreement | Development Milestone Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised									197,500,000
Bayer Collaboration Agreement | Sales-based Milestone Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised									$ 490,000,000.0
Bayer Collaboration Agreement | Stock Purchase Agreement
Research Collaboration And License Agreements [Line Items]
Fair value of the shares sold			2,900,000
Additional consideration received			$ 2,900,000
Number of contracts to be combined | Contract			2
Pfizer, Inc.
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised							$ 1,000,000.0	$ 1,200,000
Upfront non-refundable payment and certain additional payments received					$ 28,000,000.0
Pfizer, Inc. | Development Milestone Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised			$ 225,000,000
Pfizer, Inc. | Sales-based Milestone Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised			550,000,000
Pfizer, Inc. | Option Exercised
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised			4,900,000
Account receivable			2,400,000
Pfizer, Inc. | Option Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised			37,500,000
Genentech, Inc. and F. Hoffman-La Roche Ltd.
Research Collaboration And License Agreements [Line Items]
Upfront non-refundable payment and certain additional payments received	$ 34,500,000	$ 11,000,000.0
Number of designated targets | Target	10
Genentech, Inc. and F. Hoffman-La Roche Ltd. | Development Milestone Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised	$ 44,000,000.0
Genentech, Inc. and F. Hoffman-La Roche Ltd. | Option Payments | Maximum
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised	27,500,000
Genentech, Inc. and F. Hoffman-La Roche Ltd. | Regulatory Milestone Payments
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised	52,500,000
Genentech, Inc. and F. Hoffman-La Roche Ltd. | Commercial Milestones
Research Collaboration And License Agreements [Line Items]
Contract revenue receivable if milestones achieved or options for all targets exercised	$ 60,000,000.0
Bayer and Pfizer Collaboration Agreement
Research Collaboration And License Agreements [Line Items]
Changes in deferred revenue due to additions to deferred revenue			$ 6,400,000