|
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 | |||||||||||||||||||||||||