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:
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]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term Loan Original Amount	0		1,250,000,000
Long-term debt:
Long-term debt, face amount			847,100,000
Senior Notes - $700 Million [Member]
Long-term debt:
Long-term debt, face amount	700,000,000		700,000,000
Senior Notes - $1.3 Billion [Member]
Long-term debt:
Long-term debt, face amount	1,300,000,000.0		1,300,000,000.0
Senior Notes - $400 Million [Member]
Long-term debt:
Long-term debt, face amount	400,000,000		400,000,000
Senior Notes - $500 Million [Member]
Long-term debt:
Long-term debt, face amount	500,000,000.0		500,000,000.0
Revolving Loan [Member]
Long-term debt:
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]
Receivables:
Receivables, carrying value	44,600,000		52,500,000
Long-term debt:
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]
Receivables:
Receivables, carrying value	16,700,000		22,300,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member] | ArcelorMittal USA - Receivable [Member]
Receivables:
Receivables, carrying value	17,400,000		19,300,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Value [Member] | Other Credit Receivable [Member]
Receivables:
Receivables, carrying value	10,500,000		10,900,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member]
Receivables:
Receivables, fair value	45,700,000		53,500,000
Long-term debt:
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]
Receivables:
Receivables, fair value	16,100,000		21,300,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | ArcelorMittal USA - Receivable [Member]
Receivables:
Receivables, fair value	19,100,000		21,300,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | Other Credit Receivable [Member]
Receivables:
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]
Long-term debt:
Term loan, carrying value	0		753,000,000
Significant Other Observable Inputs (Level 2) [Member] | Term Loan - $1.25 Billion [Member] | Fair Value [Member]
Long-term debt:
Term loan, fair value	0		753,000,000
Significant Other Observable Inputs (Level 2) [Member] | Senior Notes - $700 Million [Member] | Carrying Value [Member]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
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]
Long-term debt:
Senior notes, fair value	527,700,000		528,400,000.0
Significant Other Observable Inputs (Level 2) [Member] | Revolving Loan [Member] | Carrying Value [Member]
Long-term debt:
Revolving loan, carrying value	550,000,000		325,000,000
Significant Other Observable Inputs (Level 2) [Member] | Revolving Loan [Member] | Fair Value [Member]
Long-term debt:
Revolving loan, fair value	$ 550,000,000		$ 325,000,000

[1] As of March 31, 2013 and December 31, 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.