Stock-Based Compensation - Assumptions (Details) - Options	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair value of the options granted, estimated using assumptions
Expected term (in years)	6 years 3 months	6 years 3 months
Expected volatility, minimum	77.00%	78.00%
Expected volatility, maximum	79.00%	80.00%
Risk-free interest-rate, minimum	2.22%	1.83%
Risk-free interest-rate, maximum	2.99%	2.22%
Dividend yield (in percent)	0.00%	0.00%
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%
Consultants
Fair value of the options granted, estimated using assumptions
Expected term (in years)	9 years 8 months 12 days
Expected volatility, minimum		76.00%
Expected volatility, maximum		85.00%
Expected volatility	84.00%
Risk-free interest-rate, minimum		2.20%
Risk-free interest-rate, maximum		2.40%
Risk-free interest-rate	3.01%
Dividend yield (in percent)	0.00%	0.00%
Consultants \| Minimum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		9 years 2 months 12 days
Consultants \| Maximum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		10 years

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

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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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- Definition

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

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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