Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Accounting Policies [Line Items]
Revenue recognized		$ 0		$ 0
Number of reportable segments | Segment			1
Number of operating segments | Segment			1
Debt instrument remaining maturity period at date of purchase			3 months
Impairment of long-lived assets	$ 0	0	$ 0	0
Amount of gross receipts during period					$ 5,000,000
Expected dividend yield			0.00%
Deferred offering costs					$ 2,700,000
Net unrealized (loss) gain on short-term investments	$ 12,000	$ (10,000)	$ (17,000)	$ 1,000
Maximum
Accounting Policies [Line Items]
Research and development arrangement with federal government, customer funding to offset costs incurred						$ 250,000
Novartis Agreement
Accounting Policies [Line Items]
Description of customer payment terms			The Company performs credit evaluations of its customer, and the risk with respect to accounts receivable is further mitigated by the short duration of customer payment terms, generally within 60 days, and the pedigree of the customer base.
Percentage of revenue contributed by related party	100.00%		100.00%
Novartis Agreement | Maximum
Accounting Policies [Line Items]
Customer payment terms			60 days