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ASSET RETIREMENT OBLIGATIONS AND RESTRICTED CASH - Narrative (Details) $ in Millions | 12 Months Ended
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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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- Definition Risk-free interest rate assumption used in valuing an instrument. + References 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 + Details
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