STOCKHOLDERS' EQUITY - Restricted Stock (Details) - 2016 Incentive Plan - Restricted Stock - USD ($) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Stock-based compensation
Weighted average grant date price (in dollars per share)	$ 5.47	$ 7.07
Unrecognized compensation expense other than options	$ 8.6	$ 5.7
Weighted average remaining vesting period	1 year 2 months 12 days	1 year 3 months 18 days
Minimum
Stock-based compensation
Grant date price (in dollars per share)	$ 3.75	$ 6.08
Maximum
Stock-based compensation
Grant date price (in dollars per share)	$ 5.65	$ 7.75
Employees and non-employee directors
Stock-based compensation
Number of shares granted	2.3	2.0
Employee
Stock-based compensation
Vesting period	3 years
Percentage of awards other than options vesting on the annual anniversary date of the grant	33.33%
Non-employee director
Stock-based compensation
Vesting period	6 months

Represents the market price of equity instruments, other than options, on date of grant.

No definition available.

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- Definition

Represents the weighted average market price of equity instruments, other than options, on date of grant.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of awards other than options which vest annually on the anniversary date of the award.

+ References

No definition available.

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- Definition

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.

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

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, 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 (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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