Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments And Hedging Activities (Narrative) (Detail)

v2.4.0.6
Derivative Instruments And Hedging Activities (Narrative) (Detail)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended
Jun. 30, 2011
USD ($)
Jun. 30, 2012
USD ($)
Jun. 30, 2011
USD ($)
Dec. 31, 2011
USD ($)
Jun. 30, 2012
Product Revenue [Member]
USD ($)
Jun. 30, 2012
Product Revenue [Member]
USD ($)
Jun. 30, 2012
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
USD ($)
Jun. 30, 2012
Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2012
Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2012
Australian Hedge Contracts [Member]
USD ($)
Jun. 30, 2011
Australian Hedge Contracts [Member]
Jun. 30, 2012
Canadian Hedge Contracts [Member]
USD ($)
Jun. 30, 2011
Foreign Exchange Contract [Member]
USD ($)
Jun. 30, 2012
Foreign Exchange Contract [Member]
USD ($)
Jun. 30, 2011
Foreign Exchange Contract [Member]
USD ($)
Dec. 31, 2011
Foreign Exchange Contract [Member]
USD ($)
Jun. 30, 2011
Foreign Exchange Contract [Member]
Consolidated Thompson [Member]
USD ($)
Jun. 30, 2011
Foreign Exchange Contract [Member]
Consolidated Thompson [Member]
USD ($)
Jan. 11, 2011
Foreign Exchange Contract [Member]
Consolidated Thompson [Member]
CAD
Jun. 30, 2012
Customer Contracts [Member]
USD ($)
Dec. 31, 2011
Customer Contracts [Member]
USD ($)
Jun. 30, 2012
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2011
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2012
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2011
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2012
Provisional Pricing Arrangements [Member]
USD ($)
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
USD ($)
Jun. 30, 2011
Provisional Pricing Arrangements [Member]
Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Jun. 30, 2011
Provisional Pricing Arrangements [Member]
Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Notional amounts of outstanding exchange rate contracts                   $ 425.0   $ 558.0       $ 400.0                          
Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts                   5.6   5.2                                  
Notional amount of foreign currency derivative instruments not designated as hedging instruments                               15.0     4,700.0                    
Amount of gain/(loss) recognized in income on derivative 50.4 0.3 106.7   96.1 96.1             7.0 0.3 11.4   41.5 93.1                      
Foreign currency spot rate                     1.07                                    
Amount of gain/(loss) recognized in income on derivative               2.2 2.2                         42.6 46.5 82.0 71.1     289.4 309.4
Derivative assets   74.8   82.1     2.0                         61.4 72.9         1.3 1.2    
Derivative liabilities             4.2                                     11.6 19.5    
Accounts receivable   $ 310.8   $ 304.2                                           $ 19.2 $ 83.8