ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Environmental	$ 9.1	$ 15.7
Mine Reclamation and Closing Liability, current and noncurrent	238.9	249.4
Total environmental and mine closure obligations	248.0	265.1
Less current portion	12.2	12.3
Long term environmental and mine closure obligations	235.8	252.8
Previously Owned Or Operating Facilities [Member] \| LTV Steel Mining Company [Member]
Loss Contingencies [Line Items]
Mine closure	19.1	18.3
Owned Or Operating Facilities [Member] \| U.S. Iron Ore [Member]
Loss Contingencies [Line Items]
Mine closure	85.1	81.2
Owned Or Operating Facilities [Member] \| Eastern Canadian Iron Ore [Member]
Loss Contingencies [Line Items]
Mine closure	75.0	88.9
Owned Or Operating Facilities [Member] \| Asia Pacific Iron Ore [Member]
Loss Contingencies [Line Items]
Mine closure	20.2	22.4
Owned Or Operating Facilities [Member] \| North American Coal [Member]
Loss Contingencies [Line Items]
Mine closure	$ 39.5	$ 38.6

Environmental Loss Contingency And Mine Reclamation And Closing Liability Current

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Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent

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Amount of environmental loss contingencies, such as presence of hazardous waste, relevant information from reports issued by regulators, and estimated costs to achieve compliance with regulatory requirements. As well as, the amount of a reclamation and mine closing liability that is associated with a legal obligation for the closure and reclamation of a mine including the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas.

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Amount of a reclamation and mine closing liability that is associated with a legal obligation for the closure and reclamation of a mine including the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas.

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