Summary of Significant Accounting Policies (Details)	12 Months Ended
Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment
Fair Value Measurements
Transfers between level 1 and level 2	$ 0	$ 0
Transfers between level 2 and level 1	0	0
Asset transfers into level 3	0	0
Asset transfers out of level 3	0	0
Cash and Cash Equivalents
Cash equivalents	$ 13,900,000	$ 38,600,000
Segment Information
Number of operating segments \| segment	1	1
Laboratory equipment \| Minimum
Property and Equipment
Estimated useful lives (in years)	3 years
Laboratory equipment \| Maximum
Property and Equipment
Estimated useful lives (in years)	5 years
Computer software
Property and Equipment
Estimated useful lives (in years)	3 years
Computer equipment
Property and Equipment
Estimated useful lives (in years)	3 years
Furniture and fixtures
Property and Equipment
Estimated useful lives (in years)	5 years

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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