STOCK BASED COMPENSATION - Summary of Assumptions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Volatility factor of the expected market price of common stock (as a percent)		74.00%
Weighted-average expected life of option	3 years 6 months	5 years	5 years
Weighted-average grant date fair value (in dollars per share)	$ 2.99	$ 2.36	$ 0.49
Risk-free interest rate, low end of range (as a percent)	1.46%	1.13%	1.10%
Risk-free interest rate, high end of range (as a percent)	1.60%	1.21%	1.79%
Volatility factor of the expected market price of common stock, low end of range (as a percent)	72.00%		73.00%
Volatility factor of the expected market price of common stock, high end of range (as a percent)	74.00%		74.00%
Additional disclosures
Fair value of awards vesting in the period	$ 1.3	$ 1.3	$ 1.5
Unrecognized compensation expense on non-vested stock options (in dollars)	$ 0.7	$ 1.4	$ 1.6
Non-vested stock options outstanding (in shares)	1.5	2.5	4.2
Weighted-average period of recognition	1 year 3 months 18 days	1 year 7 months 6 days	1 year 7 months 6 days
Allocated Share-based Compensation Expense	$ 1.4	$ 1.0	$ 1.3
Minimum
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)	0.31%	0.24%	0.00%
Maximum
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)	0.36%	0.27%	1.15%

Aggregate number of option awards made to employees under a stock option plan or plans, that have yet to vest.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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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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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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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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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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- Definition

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

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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- Definition

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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