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SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Discontinued Operation (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Income (loss) from discontinued operations, net of tax | $ 1 | $ (2) | $ 88
Operating income (loss) | (142) | 429 | 673
Foreign Currency Transaction Gain (Loss), Realized | $ 0 | $ 0 | 228
Asia Pacific Iron Ore [Member] |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Operating income (loss) |  |  | (105)
Foreign Currency Transaction Gain (Loss), Realized |  |  | $ 228

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