BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2020
USD ($)
employees
|
Dec. 31, 2019
USD ($)
|
Dec. 31, 2018
USD ($)
|
|
| Basis of Presentation and Significant Accounting Policies [Line Items] | Ìý | Ìý | Ìý |
| Entity Number of Employees | employees | 25,000 | Ìý | Ìý |
| Foreign Currency Transaction Gain (Loss), Realized | $ | $ 0 | $ 0 | $ 228 |
| Asia Pacific Iron Ore [Member] | Ìý | Ìý | Ìý |
| Basis of Presentation and Significant Accounting Policies [Line Items] | Ìý | Ìý | Ìý |
| Foreign Currency Transaction Gain (Loss), Realized | $ | Ìý | Ìý | $ 228 |
| Workforce Subject to Collective Bargaining Arrangements [Member] | Ìý | Ìý | Ìý |
| Basis of Presentation and Significant Accounting Policies [Line Items] | Ìý | Ìý | Ìý |
| Entity Number of Employees | employees | 18,500 | Ìý | Ìý |
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- Definition Basis of Presentation and Significant Accounting Policies No definition available.
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- Definition Number of persons employed by the Entity No definition available.
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- Definition Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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