STOCK OPTIONS STOCK OPTIONS - Fair Value Assumptions (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option value (in dollars per share)	$ 7.70	$ 2.40	$ 3.09
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected volatility - low (as a percent)	64.90%	60.90%	62.10%
Expected volatility - high (as a percent)	66.40%	68.80%	68.00%
Expected term (in years)		6 years	6 years
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option value (in dollars per share)	$ 7.15	$ 1.46	$ 1.73
Risk-free rate (as a percent)	1.70%	1.90%	1.50%
Expected term (in years)	4 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option value (in dollars per share)	$ 7.91	$ 3.04	$ 2.34
Risk-free rate (as a percent)	2.60%	2.50%	1.90%
Expected term (in years)	6 years

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.

+ References

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.

+ References

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.

+ References

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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

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

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
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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