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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)

v2.4.0.6
Fair Value Of Financial Instruments (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Long-term debt: Ìý Ìý
Total long-term debt $ 3,583.8 $ 3,608.7
Carrying Value [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 57.9 [1] 58.8 [1]
Long-term debt: Ìý Ìý
Customer borrowings 4.6 5.1
Total long-term debt 3,588.4 3,613.8
Carrying Value [Member] | Customer Supplemental Payments [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 22.3 22.3
Carrying Value [Member] | ArcelorMittal USA - Receivable [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 24.8 26.5
Carrying Value [Member] | Other Credit Receivable [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 10.8 10.0
Fair Value [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 60.6 [1] 61.5 [1]
Long-term debt: Ìý Ìý
Customer borrowings 4.6 5.1
Long-term debt noncurrent fair value 3,862.1 3,825.6
Fair Value [Member] | Customer Supplemental Payments [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 21.2 20.8
Fair Value [Member] | ArcelorMittal USA - Receivable [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 28.6 30.7
Fair Value [Member] | Other Credit Receivable [Member]
Ìý Ìý
Long-term receivables: Ìý Ìý
Receivables 10.8 10.0
Term Loan - $1.25 Billion [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Term loan 1,250.0 1,250.0
Term Loan - $1.25 Billion [Member] | Carrying Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Term loan 872.2 897.2
Term Loan - $1.25 Billion [Member] | Fair Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Term loan 872.2 897.2
Senior Notes - $700 Million [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 700.0 700.0
Senior Notes - $700 Million [Member] | Carrying Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 699.3 699.3
Senior Notes - $700 Million [Member] | Fair Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 738.7 726.4
Senior Notes - $1.3 Billion [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 1,300.0 1,300.0
Senior Notes - $1.3 Billion [Member] | Carrying Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 1,289.2 1,289.2
Senior Notes - $1.3 Billion [Member] | Fair Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 1,439.1 1,399.4
Senior Notes - $400 Million [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 400.0 400.0
Senior Notes - $400 Million [Member] | Carrying Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 398.1 398.0
Senior Notes - $400 Million [Member] | Fair Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 453.6 448.8
Senior Notes - $325 Million [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 325.0 325.0
Senior Notes - $325 Million [Member] | Carrying Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes 325.0 325.0
Senior Notes - $325 Million [Member] | Fair Value [Member]
Ìý Ìý
Long-term debt: Ìý Ìý
Senior notes $ 353.9 $ 348.7
[1] Includes current portion.