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QUARTERLY RESULTS OF OPERATIONS (Narrative) (Details)
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12 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | |||||||
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Dec. 31, 2012
USD ($)
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Dec. 31, 2011
USD ($)
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Dec. 31, 2010
USD ($)
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Sep. 30, 2011
Empire [Member]
USD ($)
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Sep. 30, 2011
Empire [Member]
USD ($)
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Dec. 31, 2011
Empire [Member]
USD ($)
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Sep. 30, 2011
Arcelor Mittal [Member]
USD ($)
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Dec. 31, 2011
Arcelor Mittal [Member]
USD ($)
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Dec. 31, 2012
Empire [Member]
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Sep. 30, 2011
Empire [Member]
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Dec. 31, 2012
Sonoma [Member]
Asia Pacific Coal [Member]
AUD
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Dec. 31, 2012
Bloom Lake [Member]
USD ($)
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Dec. 31, 2012
Wabush [Member]
USD ($)
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Dec. 31, 2012
Wabush [Member]
USD ($)
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Feb. 28, 2010
Wabush [Member]
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Dec. 31, 2012
MRRT Starting Base Deferred Tax Asset, Unrealizable [Member]
USD ($)
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Dec. 31, 2012
Deferred Tax Asset, Alternative Minimum Tax Credit Not Utilized [Member]
USD ($)
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| Immaterial Errors | |||||||||||||||||
| Noncontrolling interest | 21.00% | ||||||||||||||||
| Adjustment to record noncontrolling interest | $ 84,000,000 | $ 84,000,000 | |||||||||||||||
| Adjustment to record noncontrolling interest, increase to Income from Continuing Operations | 16,100,000 | 16,100,000 | |||||||||||||||
| Adjustment to record noncontrolling interest, decrease to Net Income Attributable to Cliffs Shareholders | 67,900,000 | 67,900,000 | |||||||||||||||
| Error Correction to Earnings Per Share Basic | $ (0.47) | $ (0.49) | |||||||||||||||
| Error Correction To Earnings Per Share, Diluted | $ (0.47) | $ (0.48) | |||||||||||||||
| Adjustment to record noncontrolling interest, decrease in Retained Earnings | 67,900,000 | ||||||||||||||||
| Adjustment to record noncontrolling interest, increase in Noncontrolling Interest | 84,000,000 | ||||||||||||||||
| Reclassification of amounts to Product revenues | 46,000,000 | 46,000,000 | 54,100,000 | 54,100,000 | |||||||||||||
| Discontinued Operations | |||||||||||||||||
| Ownership Interest | 79.00% | 45.00% | 73.20% | ||||||||||||||
| Proceeds from sale of economic interest | 141,000,000 | ||||||||||||||||
| Goodwill impairment | 1,000,000,000 | 27,800,000 | 997,300,000 | 2,700,000 | 2,700,000 | ||||||||||||
| Impairment of goodwill and other long-lived assets | 1,049,900,000 | 27,800,000 | 0 | 49,900,000 | |||||||||||||
| Income tax expense | $ 255,900,000 | $ 407,700,000 | $ 282,500,000 | $ 314,700,000 | $ 226,400,000 | ||||||||||||
| X | ||||||||||
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- Definition
Error Correction for Change In Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest No definition available.
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| X | ||||||||||
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- Definition
Error correction for amount of Net Income (Loss) attributable to noncontrolling interest. No definition available.
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| X | ||||||||||
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- Definition
Error Correction To Change In Net Income Loss No definition available.
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| X | ||||||||||
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- Definition
Error Correction to Earnings Per Share Basic No definition available.
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| X | ||||||||||
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- Definition
Error Correction To Earnings Per Share, Diluted No definition available.
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| X | ||||||||||
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- Definition
Error correction to the cumulative amount of the reporting entity's undistributed earnings or deficit. No definition available.
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| X | ||||||||||
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- Definition
Error correction to aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts. No definition available.
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| X | ||||||||||
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- Definition
Error correction to total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest). No definition available.
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| X | ||||||||||
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- Definition
The percentage of ownership of common stock or equity participation in the investee. No definition available.
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity. No definition available.
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| X | ||||||||||
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- Definition
The cash inflow from the sale of an investment interest in a joint venture that the reporting entity has not previously accounted for using consolidation or the equity method of accounting. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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