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DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2013
|
Dec. 31, 2012
|
Sep. 30, 2013
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Dec. 31, 2012
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Sep. 30, 2013
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
|
Sep. 30, 2013
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Dec. 31, 2012
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Sep. 30, 2013
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
|
Sep. 30, 2013
Interest Rate Swap [Member]
Designated as Hedging Instrument [Member]
|
Sep. 30, 2013
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Sep. 30, 2012
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Sep. 30, 2013
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Sep. 30, 2012
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Sep. 30, 2013
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Financial Instruments, Assets [Member]
|
Dec. 31, 2012
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Financial Instruments, Assets [Member]
|
Sep. 30, 2013
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]
|
Sep. 30, 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]
|
Sep. 30, 2013
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]
|
Sep. 30, 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]
|
Sep. 30, 2013
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 Financial Instruments, Assets [Member]
|
Sep. 30, 2013
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 Financial Instruments, Liabilities [Member]
|
Dec. 31, 2012
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Derivative Financial Instruments, Assets [Member]
|
Dec. 31, 2012
Provisional Pricing Arrangements [Member]
Not Designated as Hedging Instrument [Member]
U.S. Iron Ore and Eastern Canadian Iron Ore [Member]
Derivative Financial Instruments, Liabilities [Member]
|
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| Derivative [Line Items] | |||||||||||||||||||||||
| Derivative, Notional Amount | $ 333.0 | $ 400.0 | $ 453.5 | $ 630.4 | $ 250.0 | ||||||||||||||||||
| Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts | (13.4) | 1.0 | |||||||||||||||||||||
| Amount of gain/(loss) recognized in income on derivative | 53.9 | 49.8 | 113.4 | 131.8 | 24.3 | (8.1) | (6.8) | (10.3) | |||||||||||||||
| Derivative assets | 72.7 | 78.6 | 62.1 | 58.9 | 4.6 | 3.5 | |||||||||||||||||
| Derivative liabilities | $ 36.1 | $ 13.2 | $ 11.4 | $ 11.3 | |||||||||||||||||||