FAIR VALUE MEASUREMENTS - Performance-based Warrants (Details) - $ / shares	1 Months Ended	3 Months Ended
May 31, 2013	Mar. 31, 2018	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Weighted-average grant date fair value (in usd per share)	$ 3.91	$ 10.00	$ 7.32
Significant inputs:
Value of common stock (in usd per share)	$ 13.00
Expected term	5 years 3 months 18 days
Volatility	50.00%		53.00%
Risk-free interest rate	2.00%
Dividend yield	0.00%

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Risk-free interest rate assumption used in valuing an instrument.

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Price at which a dealer is willing to buy an instrument, used as an input to measure fair value.

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- Definition

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

+ 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 (d)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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