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DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Mar. 31, 2014
|
Mar. 31, 2013
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]
|
Mar. 31, 2013
Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member]
|
Mar. 31, 2014
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Product Revenues [Member]
|
Mar. 31, 2013
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Product Revenues [Member]
|
Mar. 31, 2014
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Dec. 31, 2013
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Mar. 31, 2014
Australian Dollar Foreign Exchange Contract Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Cost of Sales [Member]
|
Mar. 31, 2013
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Cost of Sales [Member]
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Dec. 31, 2013
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member]
Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
|
Mar. 31, 2014
Interest Rate Swap [Member]
Other Nonoperating Income Expense [Member]
|
Mar. 31, 2014
Interest Rate Swap [Member]
Designated as Hedging Instrument [Member]
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]
Not Designated as Hedging Instrument [Member]
|
Dec. 31, 2013
Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]
Not Designated as Hedging Instrument [Member]
|
Mar. 31, 2014
Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member]
Not Designated as Hedging Instrument [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
|
Mar. 31, 2014
Foreign Exchange Contract [Member]
Cost of Sales [Member]
|
Mar. 31, 2013
Foreign Exchange Contract [Member]
Cost of Sales [Member]
|
Mar. 31, 2014
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Mar. 31, 2013
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Product Revenues [Member]
|
Mar. 31, 2014
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Financial Instruments, Assets [Member]
|
Dec. 31, 2013
Customer Supply Agreement [Member]
Not Designated as Hedging Instrument [Member]
Derivative Financial Instruments, Assets [Member]
|
Mar. 31, 2014
Provisional Pricing Arrangements [Member]
Product Revenues [Member]
|
Mar. 31, 2013
Provisional Pricing Arrangements [Member]
Product Revenues [Member]
|
Mar. 31, 2014
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]
|
Mar. 31, 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]
|
Mar. 31, 2014
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]
|
Mar. 31, 2014
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, 2013
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, 2013
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]
|
|
| Derivative [Line Items] | |||||||||||||||||||||||||||||||||
| Derivative, Notional Amount | $ 315.0 | $ 323.0 | $ 275.7 | $ 285.9 | $ 250.0 | $ 38.6 | $ 74.8 | ||||||||||||||||||||||||||
| Gain (Loss) on Fair Value Hedge Ineffectiveness, Net | 0.2 | ||||||||||||||||||||||||||||||||
| Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | 20.7 | 21.2 | (0.9) | 0 | (6.1) | (2.9) | |||||||||||||||||||||||||||
| Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net | (12.8) | 2.0 | (0.3) | 0 | (9.1) | 1.8 | (3.4) | 0.2 | |||||||||||||||||||||||||
| Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts | (0.7) | (7.3) | (0.4) | ||||||||||||||||||||||||||||||
| Amount of gain/(loss) recognized in income on derivative | 27.7 | 24.1 | (6.1) | (2.9) | |||||||||||||||||||||||||||||
| Derivative assets | 42.0 | 55.8 | 1.3 | 3.1 | |||||||||||||||||||||||||||||
| Derivative liabilities | $ 7.4 | $ 10.3 | |||||||||||||||||||||||||||||||