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SEGMENT REPORTING (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2013
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Sep. 30, 2013
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Jun. 30, 2013
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Mar. 31, 2013
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Dec. 31, 2012
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Sep. 30, 2012
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Jun. 30, 2012
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Mar. 31, 2012
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Segment Reporting Information [Line Items] | |||||||||||
| Revenues | $ 1,515.8 | $ 1,546.6 | $ 1,488.5 | $ 1,140.5 | $ 1,535.9 | $ 1,544.9 | $ 1,579.5 | $ 1,212.4 | $ 5,691.4 | $ 5,872.7 | $ 6,563.9 |
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U.S. Iron Ore [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number Of Mines | 5 | ||||||||||
| Revenues | 2,667.9 | 2,723.3 | 3,509.9 | ||||||||
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Eastern Canadian Iron Ore [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number Of Mines | 2 | ||||||||||
| Revenues | 978.7 | 1,008.9 | 1,178.1 | ||||||||
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Asia Pacific Iron Ore [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number Of Mines | 1 | ||||||||||
| Revenues | 1,224.3 | 1,259.3 | 1,363.5 | ||||||||
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North American Coal [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Revenues | 821.9 | 881.1 | 512.1 | ||||||||
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North American Coal [Member] | Metallurgical Coal Mines [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number Of Mines | 4 | ||||||||||
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North American Coal [Member] | Thermal Coal Mines [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number Of Mines | 1 | ||||||||||
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Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
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| Segment Reporting Information [Line Items] | |||||||||||
| Number of Customers | 1 | 1 | 1,000,000 | ||||||||
| Concentration Risk, Percentage | 10.00% | ||||||||||
| Revenues | $ 1,000.0 | $ 923.7 | $ 1,400.0 | ||||||||