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Annual report pursuant to Section 13 and 15(d)

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details)

v3.3.1.900
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Current Fiscal Year End Date Ìý --12-31 Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Ìý $ (6,500,000) $ (28,200,000) $ (51,700,000) Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý (18,800,000) (31,000,000) (22,100,000) Ìý
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Ìý 5,500,000 161,400,000 141,100,000 Ìý
Accounts receivable, net Ìý 40,200,000 122,700,000 Ìý Ìý
Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Ìý 0 (14,300,000) (4,100,000) Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý 0 Ìý Ìý Ìý
Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member] | Cost of Sales [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý Ìý (17,700,000) (1,900,000) Ìý
Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member] | Not Designated as Hedging Instrument [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative, Notional Amount Ìý 0 Ìý Ìý Ìý
Foreign Exchange Contract [Member] | Other Nonoperating Income (Expense) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Ìý Ìý Ìý (600,000) Ìý
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [1] Ìý (3,600,000) (16,900,000) Ìý Ìý
Foreign Exchange Contract [Member] | Product Revenues [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Ìý (12,600,000) 0 0 Ìý
Australian Dollar Foreign Exchange Contract Hedge Designation [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Ìý (2,000,000) (13,900,000) (34,700,000) Ìý
Australian Dollar Foreign Exchange Contract Hedge Designation [Member] | Product Revenues [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net $ 6,300,000 (7,400,000) (13,200,000) (11,900,000) Ìý
Australian Dollar Foreign Exchange Contract Hedge Designation [Member] | Designated as Hedging Instrument [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative, Notional Amount Ìý 0 220,000,000 Ìý Ìý
Australian Dollar Foreign Exchange Contract Hedge Designation [Member] | Designated as Hedging Instrument [Member] | Accumulated Other Comprehensive Income (Loss) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] 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 0 Ìý Ìý Ìý
Australian Dollar Foreign Exchange Contracts Dedesignated [Member] | Not Designated as Hedging Instrument [Member] | Accumulated Other Comprehensive Income (Loss) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] 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 0 Ìý Ìý Ìý
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Ìý 0 0 (12,900,000) Ìý
Canadian Dollar Foreign Exchange Contracts Hedge Designation [Member] | Cost of Sales [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý 0 Ìý (8,200,000) Ìý
Interest Rate Swap [Member] | Other Nonoperating Income (Expense) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net Ìý Ìý 300,000 100,000 Ìý
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative, Notional Amount Ìý Ìý 250,000,000 Ìý Ìý
Treasury Lock [Member] | Other Nonoperating Income (Expense) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý (100,000) (100,000) (100,000) Ìý
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Ìý (100,000) Ìý Ìý Ìý
Treasury Lock [Member] | Designated as Hedging Instrument [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative, Notional Amount Ìý Ìý Ìý Ìý $ 200,000,000
Treasury Lock [Member] | Designated as Hedging Instrument [Member] | Accumulated Other Comprehensive Income (Loss) [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Ìý Ìý Ìý Ìý $ (1,300,000)
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Product Revenues [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Amount of gain/(loss) recognized in income on derivative Ìý 27,100,000 187,800,000 149,200,000 Ìý
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Other Current Assets [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative assets Ìý 5,800,000 63,200,000 Ìý Ìý
Provisional Pricing Arrangements [Member] | Product Revenues [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Ìý (1,400,000) (9,500,000) (7,500,000) Ìý
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Product Revenues [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Amount of gain/(loss) recognized in income on derivative Ìý (1,400,000) (9,500,000) (7,500,000) Ìý
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Other Current Assets [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative assets Ìý 2,000,000 0 Ìý Ìý
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | U S Iron Ore And Asia Pacific Iron Ore [Member] | Other Current Liabilities [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative liabilities Ìý 3,400,000 9,500,000 Ìý Ìý
$500 Million 3.95% 2018 Senior Notes [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Debt Instrument, Face Amount Ìý 500,000,000 500,000,000.0 Ìý Ìý
Corporate [Member] | Canadian Dollar Foreign Exchange Contracts Hedge Prior to De Designation [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Ìý Ìý (500,000) $ (1,900,000) Ìý
Amount that will be reclassified to product revenues in the next 12 months upon settlement of the related contracts Ìý Ìý 0 Ìý Ìý
Corporate [Member] | Canadian Dollar Foreign Exchange Contracts Hedge De Designated [Member] [Member] | Not Designated as Hedging Instrument [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Derivative, Notional Amount Ìý $ 0 183,000,000 Ìý Ìý
Corporate [Member] | Foreign Exchange Contract [Member] | Cost of Sales [Member] Ìý Ìý Ìý Ìý Ìý
Derivative [Line Items] Ìý Ìý Ìý Ìý Ìý
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Ìý Ìý 3,300,000 Ìý Ìý
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Ìý Ìý $ (7,300,000) Ìý Ìý
[1] At December 31, 2014 and 2013, the location of the Gain (Loss) Recognized in Income on Derivative for Foreign Exchange Contracts was Cost of goods sold and operating expenses.