|
Derivative Instruments And Hedging Activities (Narrative) (Details)
In Millions, unless otherwise specified |
3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Mar. 31, 2012
USD ($)
|
Mar. 31, 2011
USD ($)
|
Dec. 31, 2011
USD ($)
|
Mar. 31, 2011
Product Revenues [Member]
USD ($)
|
Mar. 31, 2012
Foreign Exchange Contract [Member]
USD ($)
|
Mar. 31, 2011
Foreign Exchange Contract [Member]
USD ($)
|
Dec. 31, 2011
Foreign Exchange Contract [Member]
USD ($)
|
Mar. 31, 2012
Australian Hedge Contracts [Member]
USD ($)
|
Mar. 31, 2011
Australian Hedge Contracts [Member]
USD ($)
|
Mar. 31, 2012
Australian Hedge Contracts [Member]
AUD
|
Mar. 31, 2011
Australian Hedge Contracts [Member]
AUD
|
Mar. 31, 2012
Canadian Hedge Contracts [Member]
USD ($)
|
Mar. 31, 2011
Canadian Hedge Contracts [Member]
USD ($)
|
Mar. 31, 2012
Canadian Hedge Contracts [Member]
CAD
|
Mar. 31, 2012
Customer Contracts [Member]
USD ($)
|
Dec. 31, 2011
Customer Contracts [Member]
USD ($)
|
Mar. 31, 2012
Customer Contracts [Member]
Product Revenues [Member]
USD ($)
|
Mar. 31, 2011
Customer Contracts [Member]
Product Revenues [Member]
USD ($)
|
Dec. 31, 2011
Provisional Pricing Arrangements [Member]
USD ($)
|
Mar. 31, 2012
U.S. Iron Ore, Eastern Canadian Iron Ore And Asia Pacific Iron Ore [Member]
USD ($)
|
Mar. 31, 2012
Eastern Canadian Iron Ore [Member]
Provisional Pricing Arrangements [Member]
Product Revenues [Member]
USD ($)
|
Mar. 31, 2011
Consolidated Thompson [Member]
Foreign Exchange Contract [Member]
USD ($)
|
Jan. 11, 2011
Consolidated Thompson [Member]
Foreign Exchange Contract [Member]
CAD
|
Mar. 31, 2012
Minimum [Member]
Twelve Month [Member]
|
Mar. 31, 2012
Minimum [Member]
Fifteen Month [Member]
|
Mar. 31, 2012
Maximum [Member]
Twelve Month [Member]
|
|
| Percentage of hedging policy allowed anticipated operating cost | 40.00% | 10.00% | 75.00% | |||||||||||||||||||||||
| Description of cash flow hedge risk management | The policy allows for hedging of not more than 75 percent, but not less than 40 percent for up to 12 months and not less than 10 percent for up to 15 months, occurring only during the fourth quarter of each year, of forecasted net currency exposures that are probable to occur. | |||||||||||||||||||||||||
| Notional amounts of outstanding exchange rate contracts | $ 400.0 | $ 425.0 | $ 518.4 | |||||||||||||||||||||||
| Amount of gain/(loss) recognized in income on derivative | 20.0 | 4.4 | 3.1 | 0.5 | 39.2 | 24.6 | 3.0 | |||||||||||||||||||
| Foreign currency spot rate | 1.03 | 1.03 | 1.03 | 1.03 | 1.00 | |||||||||||||||||||||
| Gain on foreign currency derivative instruments not designated as hedging instruments | 0.3 | 56.3 | 0.3 | 28.1 | ||||||||||||||||||||||
| Notional amount of foreign currency derivative instruments not designated as hedging instruments | 15.0 | 4,700.0 | ||||||||||||||||||||||||
| Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts | 4.3 | 0.7 | ||||||||||||||||||||||||
| Unrealized gains on cash flow hedging | 3.0 | 1.9 | 0.7 | |||||||||||||||||||||||
| Derivative instruments not designated as hedging instruments, gain | 23.5 | |||||||||||||||||||||||||
| Derivative assets | 78.8 | 82.1 | 65.1 | 72.9 | 1.2 | 4.1 | ||||||||||||||||||||
| Derivative liabilities | 19.5 | 1.1 | ||||||||||||||||||||||||
| Accounts receivable | $ 247.2 | $ 304.2 | $ 83.8 | |||||||||||||||||||||||