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BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)
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12 Months Ended | 12 Months Ended | 12 Months Ended | 12 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 12 Months Ended | ||||||||||||||||||||||||||||||||
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Dec. 31, 2012
USD ($)
T
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Dec. 31, 2011
USD ($)
T
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Dec. 31, 2010
USD ($)
T
|
Dec. 31, 2012
Empire [Member]
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Dec. 31, 2012
Black Label And Black Thor Chromite Deposits [Member]
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Dec. 31, 2012
Big Daddy Chromite Deposit [Member]
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Dec. 31, 2012
CLCC [Member]
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Dec. 31, 2012
Wabush [Member]
|
Dec. 31, 2012
Bloom Lake [Member]
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Dec. 31, 2012
Renewafuel [Member]
USD ($)
|
Dec. 31, 2011
Renewafuel [Member]
USD ($)
|
Dec. 31, 2010
Renewafuel [Member]
USD ($)
|
Dec. 31, 2012
U.S. Iron Ore [Member]
USD ($)
Facility
T
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Dec. 31, 2011
U.S. Iron Ore [Member]
USD ($)
T
|
Dec. 31, 2010
U.S. Iron Ore [Member]
USD ($)
|
Dec. 31, 2012
Asia Pacific Iron Ore [Member]
Cockatoo [Member]
USD ($)
|
Dec. 31, 2012
Asia Pacific Iron Ore [Member]
Cockatoo [Member]
AUD
|
Dec. 31, 2012
Asia Pacific Iron Ore [Member]
Sonoma [Member]
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Dec. 31, 2012
Latin American Iron Ore [Member]
Amapa [Member]
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Dec. 31, 2012
North American Coal [Member]
USD ($)
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Dec. 31, 2011
North American Coal [Member]
USD ($)
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Dec. 31, 2010
North American Coal [Member]
USD ($)
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Dec. 31, 2012
Eastern Canadian Iron Ore [Member]
USD ($)
Facility
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Dec. 31, 2011
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2011
Consolidated Thompson [Member]
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May 12, 2011
Consolidated Thompson [Member]
CAD
|
Dec. 31, 2012
Other Liabilities [Member]
Cockatoo [Member]
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Dec. 31, 2012
Thermal Coal Mines [Member]
North American Coal [Member]
Facility
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Dec. 31, 2012
Metallurgical Coal Mines [Member]
North American Coal [Member]
Facility
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Dec. 31, 2012
Utility Contracts [Member]
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Dec. 31, 2012
Customer Supplemental Payments [Member]
U.S. Iron Ore [Member]
USD ($)
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Dec. 31, 2011
Customer Supplemental Payments [Member]
U.S. Iron Ore [Member]
USD ($)
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Dec. 31, 2012
Take or Pay Contracts [Member]
USD ($)
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Dec. 31, 2011
Take or Pay Contracts [Member]
USD ($)
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Dec. 31, 2010
Take or Pay Contracts [Member]
USD ($)
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Dec. 31, 2012
Bloom Lake [Member]
USD ($)
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Dec. 31, 2012
Wabush [Member]
USD ($)
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Dec. 31, 2012
Wabush [Member]
USD ($)
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Feb. 28, 2010
Wabush [Member]
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Dec. 31, 2012
Sonoma [Member]
Asia Pacific Coal [Member]
AUD
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| Related Party Transaction [Line Items] | ||||||||||||||||||||||||||||||||||||||||
| Deferred revenue | $ 35,900,000 | $ 126,600,000 | $ 12,800,000 | $ 91,700,000 | ||||||||||||||||||||||||||||||||||||
| Deferred Revenue, Noncurrent | 115,600,000 | |||||||||||||||||||||||||||||||||||||||
| Finite-Lived Intangible Asset, Useful Life | 5 years | |||||||||||||||||||||||||||||||||||||||
| Number of mines (in number of facilities) | 5 | 2 | 1 | 6 | ||||||||||||||||||||||||||||||||||||
| Ownership Interest | 79.00% | 100.00% | 70.00% | 100.00% | 100.00% | 75.00% | 73.20% | 45.00% | ||||||||||||||||||||||||||||||||
| Cost per share acquired (in CAD per share) | 17.25 | |||||||||||||||||||||||||||||||||||||||
| Ownership interest, percent, after transaction | 100.00% | |||||||||||||||||||||||||||||||||||||||
| Allowance for doubtful accounts | 8,100,000 | 0 | ||||||||||||||||||||||||||||||||||||||
| Provision for Doubtful Accounts | 9,000,000 | 5,900,000 | 0 | |||||||||||||||||||||||||||||||||||||
| Inventory, LIFO reserve | 122,200,000 | 117,100,000 | 27,700,000 | 21,900,000 | ||||||||||||||||||||||||||||||||||||
| Finished goods quantity (in tons) | 1,300,000 | 1,200,000 | ||||||||||||||||||||||||||||||||||||||
| Derivatives policy, maximum percentage of amount permitted to be hedged | 75.00% | |||||||||||||||||||||||||||||||||||||||
| Derivatives policy, minimum percentage of amount permitted to be hedged, for derivatives with periods of up to 12 months | 40.00% | |||||||||||||||||||||||||||||||||||||||
| Derivatives policy, minimum percentage of amount permitted to be hedged, for derivatives with periods of up to 15 months | 10.00% | |||||||||||||||||||||||||||||||||||||||
| Lower-of-cost-or-market inventory charges | 24,400,000 | 6,600,000 | 26,100,000 | |||||||||||||||||||||||||||||||||||||
| Ownership interest, equity method investment | 50.00% | 50.00% | 45.00% | 30.00% | 50.00% | |||||||||||||||||||||||||||||||||||
| Proceeds from sale of economic interest (in AUD) | 4 | 141,000,000 | ||||||||||||||||||||||||||||||||||||||
| Estimated rehabilitation costs | 24,000,000 | |||||||||||||||||||||||||||||||||||||||
| Goodwill | 167,400,000 | 1,152,100,000 | 196,500,000 | |||||||||||||||||||||||||||||||||||||
| Impairment of goodwill | 1,000,000,000 | 27,800,000 | 997,300,000 | 2,700,000 | 2,700,000 | |||||||||||||||||||||||||||||||||||
| Equity (income) loss in ventures (net of tax) | 404,800,000 | (9,700,000) | (13,500,000) | |||||||||||||||||||||||||||||||||||||
| Impairment of goodwill and other long-lived assets | 1,049,900,000 | 27,800,000 | 0 | 16,000,000 | 49,900,000 | |||||||||||||||||||||||||||||||||||
| Reimbursement revenue | 250,800,000 | 224,300,000 | 223,400,000 | 101,000,000 | 18,300,000 | 41,900,000 | ||||||||||||||||||||||||||||||||||
| Quantity of goods in take or pay contracts (in tons) | 200,000 | 200,000 | 100,000 | |||||||||||||||||||||||||||||||||||||
| Deferred revenue | 128,400,000 | 91,700,000 | 17,100,000 | 15,800,000 | 15,100,000 | |||||||||||||||||||||||||||||||||||
| Income (loss) from discontinued operations | (100,000) | (18,500,000) | (3,100,000) | |||||||||||||||||||||||||||||||||||||
| Tax effect of discontinued operation, tax benefit | $ (9,200,000) | $ (1,500,000) | ||||||||||||||||||||||||||||||||||||||