STOCK COMPENSATION PLANS (Schedule of Compensation Costs) (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Selling, general and administrative expenses | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ (116.8) | $ (102.9) | $ (115.8) |
| INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 564.7 | 108.2 | 110.4 |
| Income Tax Expense (Benefit) | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | (475.2) | (252.4) | (12.2) |
| NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS | $ 609.5 | $ 437.8 | $ 165.1 | $ (84.3) | $ 309.9 | $ 53.4 | $ 31.8 | $ (28.1) | $ 1,128.1 | $ 367.0 | $ 174.1 |
| Earnings per common share attributable to Cliffs common shareholders - basic: | $ 2.06 | $ 1.47 | $ 0.55 | $ (0.29) | $ 1.04 | $ 0.18 | $ 0.10 | $ (0.11) | $ 3.80 | $ 1.28 | $ 0.88 |
| Earnings per common share attributable to Cliffs common shareholders - diluted: | $ 1.98 | $ 1.41 | $ 0.55 | $ (0.29) | $ 1.03 | $ 0.18 | $ 0.10 | $ (0.11) | $ 3.71 | $ 1.26 | $ 0.87 |
| Deferred Compensation, Share-based Payments [Member] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Costs and Expenses | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 1.7 | $ 1.9 | $ 1.8 |
| Selling, general and administrative expenses | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | (13.4) | (16.3) | (11.8) |
| INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 15.1 | 18.2 | 13.6 |
| Income Tax Expense (Benefit) | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 0.0 | 0.0 | 0.0 |
| NET INCOME ATTRIBUTABLE TO CLIFFS SHAREHOLDERS | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 15.1 | $ 18.2 | $ 13.6 |
| Earnings per common share attributable to Cliffs common shareholders - basic: | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 0.05 | $ 0.06 | $ 0.07 |
| Earnings per common share attributable to Cliffs common shareholders - diluted: | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 0.05 | $ 0.06 | $ 0.07 |
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- Definition Total costs of sales and operating expenses for the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Details
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