Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details)

v3.2.0.727
FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2015
USD ($)
Dec. 31, 2014
USD ($)
Mar. 31, 2015
USD ($)
Fair Value, Assets And Liabilities Components [Line Items]      
Management Estimate of 62% Fe 62.00%    
Goodwill, Impairment Loss $ 0.0 $ 73.5  
Other Asset Impairment Charges   562.0  
Global Exploration Investment in Venture [Member]      
Fair Value, Assets And Liabilities Components [Line Items]      
Equity Method Investments, Fair Value Disclosure   0.0  
Equity Method Investment, Other than Temporary Impairment   9.2  
Asia Pacific Iron Ore [Member]      
Fair Value, Assets And Liabilities Components [Line Items]      
Goodwill, Impairment Loss   73.5  
Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member]      
Fair Value, Assets And Liabilities Components [Line Items]      
Debt Instrument, Par Value $ 544.2    
Debt Instrument, Fair Value Disclosure     $ 397.2
Stated interest rate 7.75%    
Debt discount     0.27
Debt Instrument, Unamortized Discount $ 142.0   $ 147.0
Fair Value, Inputs, Level 2 [Member] | Global Exploration Investment in Venture [Member]      
Fair Value, Assets And Liabilities Components [Line Items]      
Equity Method Investments, Fair Value Disclosure   0.0  
Fair Value, Inputs, Level 2 [Member] | Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member]      
Fair Value, Assets And Liabilities Components [Line Items]      
Debt Instrument, Fair Value Disclosure $ 348.2 $ 0.0 $ 397.2