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SHAREHOLDERS' EQUITY - Summary of Assumptions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Weighted-average expected life of option	3 years 6 months	3 years 6 months	3 years 6 months
Weighted-average grant date fair value (in dollars per share)	$ 1.22	$ 1.73	$ 1.90
Risk-free interest rate, low end of range (as a percent)	0.157%	1.45%	2.67%
Risk-free interest rate, high end of range (as a percent)	0.322%	1.87%	2.89%
Volatility factor of the expected market price of common stock, low end of range (as a percent)	59.00%	58.00%	63.00%
Volatility factor of the expected market price of common stock, high end of range (as a percent)			64.00%
Additional disclosures
Fair value of awards vesting in the period	$ 0.1	$ 0.4	$ 0.7
Unrecognized compensation expense on non-vested stock options (in dollars)	$ 1.4	$ 1.0	$ 0.4
Non-vested stock options outstanding (in shares)	6.1	3.0	0.7
Weighted-average period of recognition	1 year 7 months 6 days	1 year 6 months	1 year 4 months 24 days
Stock option expense	$ 0.6	$ 0.7	$ 0.3
Minimum
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)	0.00%	0.00%	0.36%
Maximum
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)			0.53%

X

- Definition

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

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost to be recognized for option under share-based payment arrangement.

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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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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 maximum 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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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.

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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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