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GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Intangible Assets and Liabilities (Details) - USD ($) $ in Millions | Jun. 30, 2021 | Dec. 31, 2020
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Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | $ 220 | $ 220
Finite-Lived Intangible Assets, Accumulated Amortization | (37) | (32)
Finite-Lived Intangible Assets, Net | 183 | 188
Above-market supply contracts, Gross Amount | (71) | (71)
Above-market supply contracts, Accumulated Amortization | 10 | 7
Above-market supply contracts, Net | (61) | (64)
Customer relationships |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 77 | 77
Finite-Lived Intangible Assets, Accumulated Amortization | (6) | (3)
Finite-Lived Intangible Assets, Net | 71 | 74
Developed technology |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 60 | 60
Finite-Lived Intangible Assets, Accumulated Amortization | (5) | (3)
Finite-Lived Intangible Assets, Net | 55 | 57
Trade names and trademarks |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 11 | 11
Finite-Lived Intangible Assets, Accumulated Amortization | (1) | (1)
Finite-Lived Intangible Assets, Net | 10 | 10
Mining permits |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 72 | 72
Finite-Lived Intangible Assets, Accumulated Amortization | (25) | (25)
Finite-Lived Intangible Assets, Net | $ 47 | $ 47

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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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