Quarterly report pursuant to Section 13 or 15(d)

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details)

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PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Property, Plant and Equipment [Line Items]    
Depreciation And Depletion $ 28.7clf_DepreciationAndDepletionExpense $ 67.7clf_DepreciationAndDepletionExpense