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.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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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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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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STOCK-BASED COMPENSATION AND EMPLOYEE BENEFIT PLANS - Stock Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 1.7
Weighted-average period for unrecognized compensation expense	2 years 1 month 6 days
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Exercise price, not less than	100.00%
Exercise period	10 years
Compensation expense	$ 1.0	$ 1.0	$ 3.4
Grant date fair value of options (in USD per share)	$ 1.69	$ 1.22	$ 0.72
Net proceeds from exercise of employee stock options	$ 0.1	$ 0.4
Minimum \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise period	7 years
Maximum \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise period	10 years