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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)
 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2012
USD ($)
Sep. 30, 2011
USD ($)
Sep. 30, 2012
USD ($)
Sep. 30, 2011
USD ($)
Dec. 31, 2011
USD ($)
Sep. 30, 2012
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
USD ($)
Sep. 30, 2012
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
USD ($)
Sep. 30, 2012
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
USD ($)
Dec. 31, 2011
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
USD ($)
Sep. 30, 2011
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
aud_per_usd
Sep. 30, 2012
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
USD ($)
Dec. 31, 2011
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
USD ($)
Sep. 30, 2012
Foreign Exchange Contract [Member]
USD ($)
Sep. 30, 2012
Foreign Exchange Contract [Member]
USD ($)
Sep. 30, 2011
Foreign Exchange Contract [Member]
Consolidated Thompson [Member]
USD ($)
Jan. 11, 2011
Foreign Exchange Contract [Member]
Consolidated Thompson [Member]
CAD
Sep. 30, 2012
Customer Contracts [Member]
USD ($)
Dec. 31, 2011
Customer Contracts [Member]
USD ($)
Sep. 30, 2012
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2011
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2012
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2011
Customer Contracts [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2012
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2011
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Product Revenue [Member]
USD ($)
Sep. 30, 2012
Sonoma [Member]
Asia Pacific Coal [Member]
AUD
Dec. 31, 2011
Derivative Financial Instruments, Assets [Member]
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
USD ($)
Dec. 31, 2011
Derivative Financial Instruments, Liabilities [Member]
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
USD ($)
Dec. 31, 2011
Accounts Receivable [Member]
Provisional Pricing Arrangements [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
USD ($)
Sep. 30, 2012
Not Designated as Hedging Instrument [Member]
USD ($)
Dec. 31, 2011
Not Designated as Hedging Instrument [Member]
USD ($)
Sep. 30, 2012
Not Designated as Hedging Instrument [Member]
Foreign Exchange Contract [Member]
USD ($)
Dec. 31, 2011
Not Designated as Hedging Instrument [Member]
Foreign Exchange Contract [Member]
USD ($)
Sep. 30, 2012
Not Designated as Hedging Instrument [Member]
Customer Contracts [Member]
USD ($)
Dec. 31, 2011
Not Designated as Hedging Instrument [Member]
Customer Contracts [Member]
USD ($)
Sep. 30, 2012
Not Designated as Hedging Instrument [Member]
Provisional Pricing Arrangements [Member]
USD ($)
Dec. 31, 2011
Not Designated as Hedging Instrument [Member]
Provisional Pricing Arrangements [Member]
USD ($)
Sep. 30, 2012
Not Designated as Hedging Instrument [Member]
Liabilities Of Assets Held For Sale [Member]
Foreign Exchange Contract [Member]
USD ($)
Dec. 31, 2011
Not Designated as Hedging Instrument [Member]
Liabilities Of Assets Held For Sale [Member]
Foreign Exchange Contract [Member]
USD ($)
Derivative liability, fair value $ 13,000,000 Ìý $ 13,000,000 Ìý $ 23,000,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý $ 11,700,000 $ 19,500,000 ÌýÌý ÌýÌý ÌýÌý ÌýÌý ÌýÌý ÌýÌý ÌýÌý ÌýÌý
Notional amounts of outstanding exchange rate contracts Ìý Ìý Ìý Ìý Ìý Ìý Ìý 420,000,000 400,000,000 Ìý 645,700,000 0 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts Ìý Ìý Ìý Ìý Ìý Ìý Ìý 8,700,000 Ìý Ìý 6,200,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Ownership interest, percent Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 45.00% Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Proceeds from Divestiture of Interest in Joint Venture Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 141,000,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Amount of gain/(loss) recognized in income on derivative 0 (6,200,000) 300,000 100,500,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 1,100,000 1,100,000 93,100,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Foreign Currency Spot Rate Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 1.04 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Assets Held-for-sale, Current 156,600,000 Ìý 156,600,000 Ìý 159,900,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý 1,100,000 1,100,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Notional amount of foreign currency derivative instruments not designated as hedging instruments Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 4,700,000,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Amount of gain/(loss) recognized in income on derivative Ìý Ìý Ìý Ìý Ìý (10,300,000) (10,300,000) Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 49,800,000 53,800,000 131,800,000 124,900,000 623,500,000 193,000,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Derivative assets 78,300,000 Ìý 78,300,000 Ìý 82,100,000 1,400,000 1,400,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 54,500,000 72,900,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý 1,200,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Derivative liabilities Ìý Ìý Ìý Ìý Ìý 11,700,000 11,700,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý 19,500,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Accounts receivable $ 285,900,000 Ìý $ 285,900,000 Ìý $ 287,900,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý $ 83,800,000 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý