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ASSET RETIREMENT OBLIGATIONS AND RESTRICTED CASH - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Schedule of Asset Retirement Obligations [Line Items]
Inflation rate	2.00%
Undiscounted decommissioning liability	$ 41
Minimum
Schedule of Asset Retirement Obligations [Line Items]
Fair value assumptions, risk free interest rate	9.50%
Maximum
Schedule of Asset Retirement Obligations [Line Items]
Fair value assumptions, risk free interest rate	11.50%

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Inflation rate

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- Definition

[Line Items] for Schedule of Asset Retirement Obligations [Table]

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Undiscounted Decommissioning Liability

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- Definition

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

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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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