STOCK-BASED COMPENSATION - RSU activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
STOCK-BASED COMPENSATION
Number of Shares, Non-vested at beginning of period	381,167	677,734	1,621,235
Number of Shares, Granted RSUs	267,000	176,000	48,600
Number of Shares, Vested	(194,833)	(472,567)	(992,101)
Number of Shares, Non-vested at end of period	453,334	381,167	677,734
Weighted Average Fair Value at Grant Date, Non-vested at beginning of period	$ 6.39	$ 6.44	$ 6.38
Weighted Average Fair Value at Grant Date, Granted RSUs	4.15	6.49	7.46
Weighted Average Fair Value at Grant Date, Vested	5.98	6.20	6.45
Weighted Average Fair Value at Grant Date, Non-vested at end of period	$ 5.00	$ 6.39	$ 6.44

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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