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Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE OF FINANCIAL INSTRUMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details)

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FAIR VALUE OF FINANCIAL INSTRUMENTS (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Long-term debt: Ìý Ìý
Long-term debt, face amount $ 4,650,000,000 $ 5,497,100,000
Total long-term debt, carrying value 3,433,000,000 3,960,700,000
Term Loan - $1.25 Billion [Member]
 Ìý Ìý
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Ìý Ìý
Term Loan Original Amount 0 1,250,000,000
Long-term debt: Ìý Ìý
Long-term debt, face amount Ìý 847,100,000
Senior Notes - $700 Million [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Long-term debt, face amount 700,000,000 700,000,000
Senior Notes - $1.3 Billion [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Long-term debt, face amount 1,300,000,000.0 1,300,000,000.0
Senior Notes - $400 Million [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Long-term debt, face amount 400,000,000 400,000,000
Senior Notes - $500 Million [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Long-term debt, face amount 500,000,000.0 500,000,000.0
Revolving Loan [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Long-term debt, face amount 1,750,000,000.00 1,750,000,000.00
Revolving loan, carrying value 550,000,000 [1] 325,000,000 [1]
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, carrying value 44,600,000 52,500,000
Long-term debt: Ìý Ìý
Total long-term debt, carrying value 3,433,000,000 3,960,700,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member] | Customer Supplemental Payments [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, carrying value 16,700,000 22,300,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member] | ArcelorMittal USA - Receivable [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, carrying value 17,400,000 19,300,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member] | Other Credit Receivable [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, carrying value 10,500,000 10,900,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, fair value 45,700,000 53,500,000
Long-term debt: Ìý Ìý
Total long-term debt, fair value 3,801,100,000 4,354,800,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | Customer Supplemental Payments [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, fair value 16,100,000 21,300,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | ArcelorMittal USA - Receivable [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, fair value 19,100,000 21,300,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | Other Credit Receivable [Member]
 Ìý Ìý
Receivables: Ìý Ìý
Receivables, fair value 10,500,000 10,900,000
Significant Other Observable Inputs (Level 2) [Member] | Term Loan - $1.25 Billion [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Term loan, carrying value 0 753,000,000
Significant Other Observable Inputs (Level 2) [Member] | Term Loan - $1.25 Billion [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Term loan, fair value 0 753,000,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $700 Million [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, carrying value 699,400,000 699,400,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $700 Million [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, fair value 751,400,000 759,400,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $1.3 Billion [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, carrying value 1,289,400,000 1,289,400,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $1.3 Billion [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, fair value 1,513,200,000 1,524,700,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $400 Million [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, carrying value 398,300,000 398,200,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $400 Million [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, fair value 458,800,000 464,300,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $500 Million [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, carrying value 495,900,000 495,700,000.0
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $500 Million [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes, fair value 527,700,000 528,400,000.0
Significant Other Observable Inputs (Level 2) [Member] | Revolving Loan [Member] | Carrying Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Revolving loan, carrying value 550,000,000 325,000,000
Significant Other Observable Inputs (Level 2) [Member] | Revolving Loan [Member] | Fair Value [Member]
 Ìý Ìý
Long-term debt: Ìý Ìý
Revolving loan, fair value $ 550,000,000 $ 325,000,000
[1] As of MarchÌý31, 2013 and DecemberÌý31, 2012, $550.0 million and $325.0 million revolving loans were drawn under the credit facility, respectively, and the principal amount of letter of credit obligations totaled $27.7 million for each period, thereby reducing available borrowing capacity to $1.2 billion and $1.4 billion for each period, respectively.