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Debt And Credit Facilities (Narrative) (Details)
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6 Months Ended | 12 Months Ended | 12 Months Ended | 12 Months Ended | 0 Months Ended | 1 Months Ended | 0 Months Ended | 0 Months Ended | ||||||||||||||||||||||||||||||||
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Dec. 31, 2011
USD ($)
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Dec. 31, 2011
USD ($)
years
months
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Dec. 31, 2010
USD ($)
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Mar. 31, 2011
USD ($)
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Sep. 20, 2010
USD ($)
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Oct. 29, 2009
USD ($)
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Dec. 31, 2011
Senior Notes30 Year Tranche [Member]
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Mar. 31, 2011
Senior Notes30 Year Tranche [Member]
USD ($)
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Sep. 20, 2010
Senior Notes30 Year Tranche [Member]
USD ($)
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Dec. 31, 2011
Senior Notes10 Year Tranche [Member]
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Mar. 31, 2011
Senior Notes10 Year Tranche [Member]
USD ($)
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Sep. 20, 2010
Senior Notes10 Year Tranche [Member]
USD ($)
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Sep. 22, 2010
Revolving Credit Facility [Member]
USD ($)
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Mar. 31, 2010
Revolving Credit Facility [Member]
USD ($)
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Dec. 31, 2011
Revolving Credit Facility [Member]
USD ($)
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Aug. 11, 2011
Revolving Credit Facility [Member]
USD ($)
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Dec. 31, 2010
Revolving Credit Facility [Member]
USD ($)
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Aug. 11, 2011
Credit Facility Amendment [Member]
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Sep. 30, 2010
Senior Notes 700 Million Due 2021 [Member]
USD ($)
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Dec. 31, 2011
Unsecured Credit Facility [Member]
USD ($)
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Aug. 11, 2011
Unsecured Credit Facility [Member]
USD ($)
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Dec. 31, 2011
Senior Notes Due 2013 [Member]
USD ($)
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Jun. 25, 2008
Senior Notes Due 2013 [Member]
USD ($)
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Jun. 25, 2008
Senior Notes Due 2015 [Member]
USD ($)
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May 27, 2010
Amapa's Debt [Member]
USD ($)
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Aug. 11, 2011
Term Loan [Member]
USD ($)
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Dec. 31, 2011
Asia Pacific Iron Ore [Member]
Credit Facility Amendment [Member]
USD ($)
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Dec. 31, 2011
Asia Pacific Iron Ore [Member]
Credit Facility Amendment [Member]
AUD
|
Dec. 31, 2011
Consolidated Thompson [Member]
USD ($)
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Aug. 11, 2011
Consolidated Thompson [Member]
USD ($)
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May 10, 2011
Consolidated Thompson [Member]
USD ($)
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Mar. 31, 2010
Cliffs Natural Resources Pty Ltd [Member]
Credit Facility Amendment [Member]
USD ($)
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Mar. 31, 2010
Cliffs Natural Resources Pty Ltd [Member]
Credit Facility Amendment [Member]
AUD
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Jun. 25, 2008
Senior Notes [Member]
USD ($)
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Apr. 13, 2011
Senior Notes [Member]
Consolidated Thompson [Member]
USD ($)
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Jun. 25, 2008
Senior Notes 325 Million [Member]
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May 17, 2010
Senior Notes 400 Million [Member]
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Mar. 17, 2010
Senior Notes 400 Million [Member]
USD ($)
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Aug. 11, 2011
Scenario, Previously Reported [Member]
Multicurrency credit agreement [Member]
USD ($)
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Oct. 29, 2009
Scenario, Previously Reported [Member]
Multicurrency credit agreement [Member]
USD ($)
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| Line of Credit Facility [Line Items] | ||||||||||||||||||||||||||||||||||||||||
| Line of credit facility capacity | $ 1,750,000,000 | |||||||||||||||||||||||||||||||||||||||
| Increase in letters of credit | 50,000,000 | |||||||||||||||||||||||||||||||||||||||
| Increase in basis, Points | 50 | |||||||||||||||||||||||||||||||||||||||
| Repayments of debt | 200,000,000 | 350,000,000 | 200,000,000 | 100,800,000 | ||||||||||||||||||||||||||||||||||||
| Credit agreement additional borrowings | 250,000,000 | |||||||||||||||||||||||||||||||||||||||
| Scheduled principal payment | 28,000,000 | |||||||||||||||||||||||||||||||||||||||
| Term loan, length of maturity, years | 5 | |||||||||||||||||||||||||||||||||||||||
| Required frequency of principal payments, term loan, months | 3 | |||||||||||||||||||||||||||||||||||||||
| Senior notes | 300,000,000 | 500,000,000 | 700,000,000 | 500,000,000 | 500,000,000 | 270,000,000 | 55,000,000 | 250,000,000 | 125,000,000 | |||||||||||||||||||||||||||||||
| Amended Total Funded Debt to EBITDA threshold | 3.5 | 3.25 | ||||||||||||||||||||||||||||||||||||||
| Face Amount of Senior Long Term Notes | 1,000,000,000 | 1,000,000,000 | 270,000,000 | 325,000,000 | 100,000,000 | 400,000,000 | ||||||||||||||||||||||||||||||||||
| Stated interest rate | 6.25% | 6.25% | 4.875% | 4.80% | 6.31% | 6.59% | 8.50% | 5.90% | ||||||||||||||||||||||||||||||||
| Discount interest rate on redemption | 40 | 35 | ||||||||||||||||||||||||||||||||||||||
| Premium on principal required to redeem notes | 101.00% | |||||||||||||||||||||||||||||||||||||||
| Redemption price, percent of principal in the event of company redemption | 100.00% | 100.00% | ||||||||||||||||||||||||||||||||||||||
| Credit facility | 1,750,000,000 | 750,000,000 | 40,800,000 | 40,000,000 | ||||||||||||||||||||||||||||||||||||
| Credit facility long term | 600,000,000 | 897,200,000 | 200,000,000 | 800,000,000 | 800,000,000 | |||||||||||||||||||||||||||||||||||
| Outstanding long term loan | 972,000,000 | 972,000,000 | 1,250,000,000 | |||||||||||||||||||||||||||||||||||||
| Weighted average interest rate | 1.84% | 2.56% | ||||||||||||||||||||||||||||||||||||||
| Outstanding bank guarantees under credit facilities | 23,500,000 | 64,700,000 | 25,200,000 | 24,700,000 | ||||||||||||||||||||||||||||||||||||
| Credit facility remaining capacity | 1,726,500,000 | 535,300,000 | 15,600,000 | 15,300,000 | ||||||||||||||||||||||||||||||||||||
| Letters of Credit Outstanding, Amount | 150,000,000 | 95,000,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments in 2012 | 74,800,000 | 74,800,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments in 2013 | 369,700,000 | 369,700,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments in 2014 | 124,600,000 | 124,600,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments in 2015 | 428,800,000 | 428,800,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments in 2016 | 299,100,000 | 299,100,000 | ||||||||||||||||||||||||||||||||||||||
| Maturities of debt instruments after 2016 | $ 2,400,000,000 | $ 2,400,000,000 | ||||||||||||||||||||||||||||||||||||||