Annual report pursuant to Section 13 and 15(d)

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details)

v2.4.0.6
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details)
12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
Dec. 31, 2010
USD ($)
Dec. 31, 2012
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
USD ($)
Dec. 31, 2011
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
USD ($)
Dec. 31, 2010
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
USD ($)
Dec. 31, 2012
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2011
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2012
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
USD ($)
Dec. 31, 2012
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
USD ($)
Dec. 31, 2011
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
USD ($)
Dec. 31, 2010
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
USD ($)
Dec. 31, 2012
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2011
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2012
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
USD ($)
Dec. 31, 2012
Treasury Lock [Member]
USD ($)
Dec. 31, 2011
Treasury Lock [Member]
USD ($)
Dec. 31, 2010
Treasury Lock [Member]
USD ($)
Dec. 31, 2011
Treasury Lock [Member]
Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2012
Treasury Lock [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
USD ($)
Dec. 31, 2012
Australian Dollar Foreign Exchange Contract Prior To De Designation [Member]
USD ($)
Dec. 31, 2011
Australian Dollar Foreign Exchange Contract Prior To De Designation [Member]
USD ($)
Dec. 31, 2010
Australian Dollar Foreign Exchange Contract Prior To De Designation [Member]
USD ($)
Jan. 11, 2011
Foreign Exchange Contract [Member]
Not Designated as Hedging Instrument [Member]
Consolidated Thompson [Member]
CAD
Dec. 31, 2011
Foreign Exchange Contract [Member]
Not Designated as Hedging Instrument [Member]
Consolidated Thompson [Member]
Changes in Fair Value of Foreign Currency Contracts, Net [Member]
USD ($)
Nov. 13, 2012
Foreign Exchange Contract [Member]
Not Designated as Hedging Instrument [Member]
Sonoma [Member]
Asia Pacific Coal [Member]
aud_per_usd
Dec. 31, 2012
Foreign Exchange Contract [Member]
Not Designated as Hedging Instrument [Member]
Sonoma [Member]
Asia Pacific Coal [Member]
Income (Loss) From Discontinued Operations [Member]
USD ($)
Dec. 31, 2012
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2011
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2010
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2012
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Assets [Member]
USD ($)
Dec. 31, 2011
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Assets [Member]
USD ($)
Dec. 31, 2010
Provisional Pricing Arrangements [Member]
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
U.S. Iron Ore [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2012
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
Product Revenues [Member]
USD ($)
Dec. 31, 2012
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
Derivative Assets [Member]
USD ($)
Dec. 31, 2012
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
Other Current Liabilities [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Derivative Assets [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Other Current Liabilities [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Accounts Receivable [Member]
USD ($)
Dec. 31, 2012
Senior Notes - $500 Million [Member]
USD ($)
Dec. 31, 2011
Senior Notes - $500 Million [Member]
USD ($)
Dec. 31, 2012
10-year Tranche - $500 million 4.80% Senior Notes due 2020 [Member]
USD ($)
Dec. 31, 2011
10-year Tranche - $500 million 4.80% Senior Notes due 2020 [Member]
USD ($)
Dec. 31, 2012
Sonoma [Member]
Asia Pacific Coal [Member]
AUD
Derivative [Line Items]                                                                                            
Notional amounts of outstanding exchange rate contracts             $ 400,000,000 $ 400,000,000         $ 630,400,000 $ 0         $ 200,000,000                                                      
Debt, length of maturity, years 5 years                                                                                          
Debt instrument, face amount 5,497,100,000 5,447,000,000                                                                               500,000,000 500,000,000 500,000,000 500,000,000  
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net 25,600,000 1,800,000 1,900,000 20,200,000 1,800,000 1,900,000       6,700,000             (1,300,000)         (1,300,000)                                                       
Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts                 6,700,000           3,400,000         100,000                                                    
Amount of gain/(loss) recognized in income on derivative                                                       171,400,000 178,000,000 120,200,000     960,700,000 809,100,000 309,400,000 (7,800,000)                    
Foreign currency spot rate                                                   1.04                                        
Ownership interest, percent                                                                                           45.00%
Notional amount of forward contracts                                                                                           141,000,000
Amount of gain/(loss) recognized in income on derivative (100,000) 101,900,000 39,800,000                                           93,100,000   (300,000)                                      
Notional amount of foreign currency derivative instruments not designated as hedging instruments                                               4,700,000,000                                            
Derivative assets 78,600,000 82,100,000                                                         58,900,000 72,900,000         3,500,000   1,200,000              
Derivative liabilities                                                                           11,300,000   19,500,000            
Accounts receivable, net $ 329,000,000 $ 287,900,000                                                                             $ 83,800,000