Stock-Based Compensation - Assumptions (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Minimum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		6 years 3 months
Maximum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		9 years 8 months 12 days
Options
Fair value of the options granted, estimated using assumptions
Expected term (in years)	6 years 3 months
Expected volatility, minimum	79.00%	77.00%
Expected volatility, maximum	95.00%	84.00%
Risk-free interest-rate, minimum	1.59%	2.22%
Risk-free interest-rate, maximum	2.67%	3.01%
Dividend yield (in percent)	0.00%	0.00%
Options \| Number of shares excess granted under the 2014 Plan
Fair value of the options granted, estimated using assumptions
Expected term (in years)	6 years 3 months
Expected volatility, minimum	77.00%
Expected volatility, maximum	79.00%
Risk-free interest-rate, minimum	2.22%
Risk-free interest-rate, maximum	2.99%
Dividend yield (in percent)	0.00%

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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No definition available.

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- Definition

The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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No definition available.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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No definition available.

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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No definition available.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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