ACQUISITIONS (Narrative) (Details)
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3 Months Ended | 12 Months Ended | 12 Months Ended | 3 Months Ended | 3 Months Ended | 3 Months Ended | 12 Months Ended | ||||||||||||||||||||||||||
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Dec. 31, 2013
USD ($)
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Sep. 30, 2013
USD ($)
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Jun. 30, 2013
USD ($)
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Mar. 31, 2013
USD ($)
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Dec. 31, 2012
USD ($)
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Sep. 30, 2012
USD ($)
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Jun. 30, 2012
USD ($)
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Mar. 31, 2012
USD ($)
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Dec. 31, 2013
USD ($)
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Dec. 31, 2012
USD ($)
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Dec. 31, 2011
USD ($)
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Dec. 31, 2013
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2012
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2011
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2012
Consolidated Thompson [Member]
USD ($)
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Dec. 31, 2011
Consolidated Thompson [Member]
USD ($)
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May 12, 2011
Consolidated Thompson [Member]
USD ($)
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May 12, 2011
Consolidated Thompson [Member]
CAD
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Dec. 31, 2011
Consolidated Thompson [Member]
Acquisition-related Costs [Member]
USD ($)
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Dec. 31, 2011
Consolidated Thompson [Member]
Fair Value Adjustment to Inventory [Member]
USD ($)
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Dec. 31, 2010
Consolidated Thompson [Member]
Fair Value Adjustment to Inventory [Member]
USD ($)
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Jun. 30, 2011
Consolidated Thompson [Member]
Initial Allocation [Member]
USD ($)
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May 12, 2011
Consolidated Thompson [Member]
Initial Allocation [Member]
USD ($)
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Jun. 30, 2011
Consolidated Thompson [Member]
Final Allocation [Member]
USD ($)
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Jun. 30, 2012
Consolidated Thompson [Member]
Final Allocation [Member]
USD ($)
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Jun. 30, 2011
Consolidated Thompson [Member]
Change [Member]
USD ($)
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Jun. 30, 2012
Consolidated Thompson [Member]
Change [Member]
USD ($)
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Dec. 31, 2012
Consolidated Thompson [Member]
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2013
Wisco [Member]
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Dec. 31, 2012
Wisco [Member]
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Dec. 31, 2011
Interest Expense, Net [Member]
Consolidated Thompson [Member]
USD ($)
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Dec. 31, 2011
Other Current Assets [Member]
Consolidated Thompson [Member]
USD ($)
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Dec. 31, 2011
Other Non-current Assets [Member]
Consolidated Thompson [Member]
USD ($)
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Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Net income | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 361,800,000 | $ (1,126,600,000) | $ 1,812,600,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 69,600,000 | $ 59,800,000 | $ 59,800,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Cost per share acquired (in CAD per share) | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 17.25 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition, Transaction Costs | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 4,600,000,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Subsidiary Or Equity Method Investee Percentage Ownership Acquired | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 17.152% | 25.00% | Ìý | Ìý | Ìý |
Pre-acquisition date Quebec mining duties tax | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 16,400,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Increase in current liabilities | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 6,100,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Increase in long-term liabilities | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 10,300,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Reduction of calculated minimum distribution payable to the minority partner | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 2,600,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Increase in goodwill | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 13,800,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Noncontrolling interest in subsidiary | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 1,075,400,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 947,600,000 | Ìý | 1,075,400,000 | Ìý | 127,800,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Acquisition-related costs | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 25,400,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Deferred debt issuance costs | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 15,700,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 1,700,000 | 14,000,000 |
Deferred debt issuance costs, accumulated amortization | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 1,900,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Write off of deferred debt issuance costs | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 38,300,000 | Ìý | Ìý |
Incremental revenue from business acquisition | 1,515,800,000 | 1,546,600,000 | 1,488,500,000 | 1,140,500,000 | 1,535,900,000 | 1,544,900,000 | 1,579,500,000 | 1,212,400,000 | 5,691,400,000 | 5,872,700,000 | 6,563,900,000 | 978,700,000 | 1,008,900,000 | 1,178,100,000 | Ìý | 571,000,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Incremental income from business acquisition | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 671,000,000 | (308,800,000) | 2,296,800,000 | Ìý | Ìý | Ìý | Ìý | 143,700,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Stepped-up value of inventory and reserves due to purchase accounting | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 59,800,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Cash portion of acquisition consideration | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 4,554,000,000 | Ìý | 4,554,000,000 | Ìý | 0 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Mineral Rights | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 4,825,600,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 4,450,000,000 | Ìý | 4,825,600,000 | Ìý | 375,600,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | 1,041,800,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | (831,500,000) | Ìý | (1,041,800,000) | Ìý | (210,300,000) | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Goodwill | $ 74,500,000 | Ìý | Ìý | Ìý | $ 167,400,000 | Ìý | Ìý | Ìý | $ 74,500,000 | $ 167,400,000 | $ 1,152,100,000 | $ 0 | $ 0 | $ 986,200,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | $ 1,026,800,000 | Ìý | $ 997,300,000 | Ìý | $ (29,500,000) | $ 997,300,000 | Ìý | Ìý | Ìý | Ìý | Ìý |