Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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-Publisher FASB
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-Topic 718
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-Section 50
-Paragraph 2
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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stock-Based Compensation - Stock based compensation expense (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Stock based compensation expense
Unrecognized compensation cost					$ 6,000,000
Compensation expense recognition period					3 years
Total stock-based compensation expense	$ 524,000	$ 90,000	$ 1,319,000	$ 138,000	$ 263,000	$ 75,000
Research and development
Stock based compensation expense
Total stock-based compensation expense	182,000	41,000	482,000	62,000	85,000	35,000
General and administrative
Stock based compensation expense
Total stock-based compensation expense	$ 342,000	$ 49,000	$ 837,000	$ 76,000	$ 178,000	$ 40,000