STOCKHOLDERS' EQUITY - RSU, PSU and SPSU activity (Details)	6 Months Ended
Jun. 30, 2021 $ / shares shares
RSU, PSU and SPSU
Shares of RSU PSU and SPSU
Balance at the beginning of the period (in shares)	4,159,261
Granted (in shares)	4,864,460
Forfeited (in shares)	(173,561)
Nonvested at the end of the period (in shares)	8,850,160
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) \| $ / shares	$ 6.27
Granted (in dollars per share) \| $ / shares	7.70
Forfeited (in dollars per share) \| $ / shares	11.91
Unvested at the end of the period (in dollars per share) \| $ / shares	$ 6.95
Tranche Years 2022 and 2023 awarded under the 2021 PSU award with grant date fair values to be determined in years 2022 and 2023, respectively	1,791,977
Total Nonvested at June 30, 2021	10,642,137
Special Performance Stock Unit \| 2021 Special PSU
Weighted Average Grant Date Fair Value
Percentage of performance target	200.00%
Percentage of free cash flow target	160.00%
Special Performance Stock Unit \| 2021 Special PSU \| Minimum
Weighted Average Grant Date Fair Value
Percentage of Performance Stock Unit Award Vesting as Percentage of Performance Target	80.00%
Special Performance Stock Unit \| 2021 Special PSU \| Maximum
Weighted Average Grant Date Fair Value
Percentage of Performance Stock Unit Award Vesting as Percentage of Performance Target	120.00%
Special Performance Stock Unit \| 2021 & 2020 Special PSU \| Minimum
Weighted Average Grant Date Fair Value
Percentage of Performance Target for Grant of Performance Stock Unit Award	50.00%
Special Performance Stock Unit \| 2021 & 2020 Special PSU \| Maximum
Weighted Average Grant Date Fair Value
Percentage of Performance Target for Grant of Performance Stock Unit Award	200.00%
Special Performance Stock Unit \| 2019 Special PSU \| Minimum
Weighted Average Grant Date Fair Value
Percentage of Performance Target for Grant of Performance Stock Unit Award	30.00%
Special Performance Stock Unit \| 2019 Special PSU \| Maximum
Weighted Average Grant Date Fair Value
Percentage of Performance Target for Grant of Performance Stock Unit Award	200.00%

Percentage of free cash flow target.

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- Definition

Represents the percentage of PSUs vesting expressed as a percentage of performance target.

+ References

No definition available.

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Percentage of performance target.

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Represents the percentage of performance target for grant of performance stock unit award.

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No definition available.

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Number of equity instruments other than options awarded for the next two fiscal years however the grant date fair values are subject to determination in that particular fiscal year under the share based compensation arrangement.

+ References

No definition available.

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Total number of equity instruments other than options outstanding including the awards for which the grant date fair values are subject to determination in that particular fiscal year under the share based compensation arrangement.

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No definition available.

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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).

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition

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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 718
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-Paragraph 2
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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