Quarterly report pursuant to Section 13 or 15(d)

Fair Value Of Financial Instruments (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Detail)

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Fair Value Of Financial Instruments (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Detail) (USD $)
6 Months Ended
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2010
Jun. 30, 2012
Customer Supply Agreement [Member]
Derivative Asset [Member]
Jun. 30, 2012
Provisional Pricing Arrangement [Member]
Derivative Asset [Member]
Jun. 30, 2012
Provisional Pricing Arrangement [Member]
Accounts Receivable [Member]
Jun. 30, 2012
Provisional Pricing Arrangement [Member]
Other Current Liabilities [Member]
Jun. 30, 2012
Hot-Rolled Steel Estimate [Member]
Market Approach [Member]
Customer Supply Agreement [Member]
Derivative Asset [Member]
Jun. 30, 2012
Hot-Rolled Steel Estimate [Member]
Market Approach [Member]
Customer Supply Agreement [Member]
Derivative Asset [Member]
Minimum [Member]
Jun. 30, 2012
Hot-Rolled Steel Estimate [Member]
Market Approach [Member]
Customer Supply Agreement [Member]
Derivative Asset [Member]
Maximum [Member]
Jun. 30, 2012
Managements Estimate Of 62% Fe [Member]
Market Approach [Member]
Provisional Pricing Arrangement [Member]
Derivative Asset [Member]
Jun. 30, 2012
Managements Estimate Of 62% Fe [Member]
Market Approach [Member]
Provisional Pricing Arrangement [Member]
Derivative Asset [Member]
Minimum [Member]
Jun. 30, 2012
Managements Estimate Of 62% Fe [Member]
Market Approach [Member]
Provisional Pricing Arrangement [Member]
Derivative Asset [Member]
Maximum [Member]
Jun. 30, 2012
Managements Estimate Of 62% Fe [Member]
Market Approach [Member]
Provisional Pricing Arrangement [Member]
Accounts Receivable [Member]
Jun. 30, 2012
Managements Estimate Of 62% Fe [Member]
Market Approach [Member]
Provisional Pricing Arrangement [Member]
Other Current Liabilities [Member]
Fair Value, Assets And Liabilities Measured On Unobservable Inputs [Line Items]                                    
Fair value measurement with unobservable inputs derivative asset range                     $ (675,000,000) $ 650,000,000 $ 775,000,000 $ (148,000,000) $ 140,000,000 $ 160,000,000    
Fair Value of derivative assets 83,900,000 69,200,000 157,900,000 64,000,000 68,100,000 45,600,000         61,400,000     3,300,000     19,200,000  
Fair Value of derivative liabilities $ (15.8) $ (1.1) $ (19.5)                                $ 15,800,000
Description of Location of Price Risk Derivatives on Balance Sheet             Derivative Assets Derivative Assets Accounts receivable Other current liabilities