FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 6 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2013
|
Jun. 30, 2012
|
Jun. 30, 2013
|
Jun. 30, 2012
|
Dec. 31, 2012
|
Jun. 30, 2013
Empire [Member]
|
Dec. 31, 2012
Empire [Member]
|
Dec. 31, 2002
Empire [Member]
|
Dec. 31, 2002
Prior [Member]
Empire [Member]
|
Dec. 31, 2002
Current [Member]
Empire [Member]
|
Jun. 30, 2013
Other Current Assets [Member]
Empire [Member]
|
Dec. 31, 2012
Other Current Assets [Member]
Empire [Member]
|
Jun. 30, 2013
U.S. Iron Ore [Member]
|
Dec. 31, 2012
U.S. Iron Ore [Member]
|
Jun. 30, 2013
Amapa [Member]
|
Dec. 31, 2012
Amapa [Member]
|
Jun. 30, 2013
Equity Method Investments [Member]
Amapa [Member]
|
Dec. 31, 2012
Equity Method Investments [Member]
Amapa [Member]
|
|
Fair Value, Assets And Liabilities Components [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Transfers out of Level 3 | $ 0 | $ 0 | $ 0 | $ 0 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Transfers into Level 3 | 0 | 0 | 0 | 0 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Management Estimate of 62% Fe | Ìý | Ìý | 62.00% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Maximum deferred portion of supplemental payments | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 22.3 | Ìý | Ìý | Ìý | Ìý | Ìý |
Supply agreement, customer receivable, stated interest rate | 9.00% | Ìý | 9.00% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Supply agreement, customer receivable, description of variable rate basis | Ìý | Ìý | prime rate | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Payments for (Proceeds from) Loans Receivable | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 22.3 | Ìý | Ìý | Ìý | Ìý | Ìý |
Other current assets | 316.3 | Ìý | 316.3 | Ìý | 321.6 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 22.3 | Ìý | Ìý | Ìý | Ìý |
Supply agreement, customer receivable, basis spread on variable rate | 3.50% | Ìý | 3.50% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of the receivable | Ìý | Ìý | Ìý | Ìý | Ìý | 16.7 | 21.3 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 21.3 | Ìý | Ìý | Ìý | Ìý |
Estimated credit-adjusted risk-free interest rate | Ìý | Ìý | Ìý | Ìý | Ìý | 2.40% | 2.85% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 2.81% | Ìý | Ìý | Ìý | Ìý |
Interest Percentage | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 46.70% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 30.00% | Ìý |
Equity Method Investments, Fair Value Disclosure | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 0 | 72.5 | Ìý | Ìý |
Percent ownership interest after transaction | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 79.00% | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Long term accounts notes and loans receivable net noncurrent | Ìý | Ìý | Ìý | Ìý | Ìý | 15.4 | 19.3 | 120.0 | Ìý | Ìý | 10.0 | 10.0 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Equity Method Investment, Other than Temporary Impairment | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 67.6 | $ 365.4 |