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ACQUISITIONS (Narrative) (Details)
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3 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended | 12 Months Ended | 12 Months Ended | 0 Months Ended | 0 Months Ended | 0 Months Ended | 0 Months Ended | 12 Months Ended | 0 Months Ended | 3 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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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, 2011
USD ($)
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Sep. 30, 2011
USD ($)
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Jun. 30, 2011
USD ($)
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Mar. 31, 2011
USD ($)
|
Dec. 31, 2012
USD ($)
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Dec. 31, 2011
USD ($)
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Dec. 31, 2010
USD ($)
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Dec. 31, 2012
Permits [Member]
Minimum [Member]
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Dec. 31, 2012
Eastern Canadian Iron Ore [Member]
USD ($)
Facility
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Dec. 31, 2011
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2010
Eastern Canadian Iron Ore [Member]
USD ($)
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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 ($)
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Feb. 02, 2010
Wabush [Member]
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Feb. 01, 2010
Wabush [Member]
Initial Allocation [Member]
USD ($)
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Feb. 02, 2010
Wabush [Member]
Initial Allocation [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 ($)
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May 12, 2011
Consolidated Thompson [Member]
Initial Allocation [Member]
USD ($)
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Jun. 30, 2012
Consolidated Thompson [Member]
Final Allocation [Member]
USD ($)
|
Jun. 30, 2012
Consolidated Thompson [Member]
Change [Member]
USD ($)
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Dec. 31, 2012
Consolidated Thompson [Member]
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2012
Wisco [Member]
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Feb. 01, 2010
Wabush [Member]
T
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Feb. 02, 2010
Wabush [Member]
USD ($)
T
|
Feb. 01, 2010
Wabush [Member]
Minimum [Member]
T
|
Feb. 01, 2010
Wabush [Member]
Initial Allocation [Member]
USD ($)
|
Dec. 31, 2010
Wabush [Member]
Final Allocation [Member]
USD ($)
|
Dec. 31, 2010
Wabush [Member]
Change [Member]
USD ($)
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Feb. 01, 2010
Wabush [Member]
Contractual Rights [Member]
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Feb. 02, 2010
Wabush [Member]
Contractual Rights [Member]
USD ($)
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Feb. 01, 2010
Wabush [Member]
Permits [Member]
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Feb. 02, 2010
Wabush [Member]
Permits [Member]
USD ($)
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Feb. 02, 2010
Wabush [Member]
Eastern Canadian Iron Ore [Member]
USD ($)
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Dec. 31, 2012
Wabush [Member]
Final Allocation [Member]
USD ($)
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Feb. 02, 2010
Wabush [Member]
Final Allocation [Member]
USD ($)
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Feb. 02, 2010
Wabush [Member]
Change [Member]
USD ($)
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Jan. 27, 2010
Freewest [Member]
USD ($)
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Jan. 27, 2010
Freewest [Member]
CAD
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Mar. 31, 2010
Freewest [Member]
USD ($)
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Dec. 31, 2009
Freewest [Member]
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Dec. 31, 2012
Freewest [Member]
Initial Allocation [Member]
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Jan. 27, 2010
Freewest [Member]
Initial Allocation [Member]
USD ($)
|
Dec. 31, 2010
Freewest [Member]
Final Allocation [Member]
USD ($)
|
Dec. 31, 2010
Freewest [Member]
Change [Member]
USD ($)
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Jan. 27, 2010
Freewest [Member]
Other Segment [Member]
USD ($)
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Oct. 06, 2010
Spider [Member]
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Jul. 26, 2010
Spider [Member]
|
Jul. 06, 2010
Spider [Member]
USD ($)
deposit
|
Jun. 30, 2010
Spider [Member]
USD ($)
|
Jun. 30, 2010
Spider [Member]
CAD
|
Jul. 06, 2010
Spider [Member]
Initial Allocation [Member]
USD ($)
|
Dec. 31, 2010
Spider [Member]
Final Allocation [Member]
USD ($)
|
Dec. 31, 2010
Spider [Member]
Change [Member]
USD ($)
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Jul. 06, 2010
Spider [Member]
Big Daddy Chromite Deposit [Member]
|
Jul. 06, 2010
Spider [Member]
Other Segment [Member]
USD ($)
|
Jul. 30, 2010
CLCC [Member]
USD ($)
|
Jul. 30, 2010
CLCC [Member]
Initial Allocation [Member]
USD ($)
|
Jun. 30, 2011
CLCC [Member]
Final Allocation [Member]
USD ($)
|
Jun. 30, 2011
CLCC [Member]
Change [Member]
USD ($)
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Jul. 30, 2010
CLCC [Member]
Construction Permits [Member]
USD ($)
|
Jul. 30, 2010
CLCC [Member]
Lease Agreements [Member]
USD ($)
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Jul. 30, 2010
CLCC [Member]
Thermal Coal [Member]
Facility
T
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Jul. 30, 2010
CLCC [Member]
Thermal Coal [Member]
Minimum [Member]
T
|
Jul. 30, 2010
CLCC [Member]
Metallurgical Coal [Member]
Facility
T
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Jul. 30, 2010
CLCC [Member]
Metallurgical Coal [Member]
Minimum [Member]
T
|
Jul. 30, 2010
CLCC [Member]
North American Coal [Member]
USD ($)
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Dec. 31, 2011
Interest Expense, Net [Member]
Consolidated Thompson [Member]
USD ($)
|
Dec. 31, 2011
Other Current Assets [Member]
Consolidated Thompson [Member]
USD ($)
|
Dec. 31, 2011
Other Non-current Assets [Member]
Consolidated Thompson [Member]
USD ($)
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| Business Acquisition [Line Items] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Net income | $ (1,126,600,000) | $ 1,812,600,000 | $ 1,019,900,000 | $ 69,600,000 | $ 59,800,000 | $ 59,800,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cost per share acquired (in CAD per share) | 17.25 | 1.00 | 0.19 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Consideration transferred, amount | 4,600,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Subsidiary or equity method investee percentage ownership acquired | 25.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pre-acquisition date Quebec mining duties tax | 16,400,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in current liabilities | 6,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in long-term liabilities | 10,300,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Reduction of calculated minimum distribution payable to the minority partner | 2,600,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in goodwill | 13,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mineral rights | 4,825,600,000 | 4,450,000,000 | 4,825,600,000 | 375,600,000 | 85,100,000 | 84,400,000 | (700,000) | 252,800,000 | 244,000,000 | (8,800,000) | 31,000,000 | 35,300,000 | 4,300,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Long-term deferred tax liabilities | 1,041,800,000 | (831,500,000) | (1,041,800,000) | (210,300,000) | (20,500,000) | 0 | 20,500,000 | (57,400,000) | (54,300,000) | 3,100,000 | (2,700,000) | (5,100,000) | (2,400,000) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Noncontrolling interest in subsidiary | 1,075,400,000 | 947,600,000 | 1,075,400,000 | 127,800,000 | 51,900,000 | 51,900,000 | 51,900,000 | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Goodwill | 1,026,800,000 | 997,300,000 | (29,500,000) | 997,300,000 | 15,400,000 | 3,100,000 | (12,300,000) | 3,100,000 | 0 | 5,700,000 | 5,700,000 | 5,700,000 | 77,100,000 | 75,200,000 | (1,900,000) | 75,200,000 | 24,700,000 | 27,800,000 | 3,100,000 | 27,800,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Acquisition-related costs | 25,400,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Deferred debt issuance costs | 15,700,000 | 1,700,000 | 14,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Deferred debt issuance costs, accumulated amortization | 1,900,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Write off of deferred debt issuance costs | 38,300,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Incremental revenue from business acquisition | 1,535,900,000 | 1,544,900,000 | 1,579,500,000 | 1,212,400,000 | 1,603,700,000 | 2,089,100,000 | 1,723,200,000 | 1,147,900,000 | 5,872,700,000 | 6,563,900,000 | 4,483,800,000 | 1,008,900,000 | 1,178,100,000 | 477,700,000 | 881,100,000 | 512,100,000 | 438,200,000 | 571,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Incremental income from business acquisition | (308,800,000) | 2,296,800,000 | 1,232,800,000 | 143,700,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Stepped-up value of inventory and reserves due to purchase accounting | 59,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percent ownership Interest | 100.00% | 100.00% | 100.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate acquisition consideration | 4,554,000,000 | 4,554,000,000 | 0 | 103,000,000 | 103,000,000 | 103,000,000 | 0 | 185,900,000 | 185,900,000 | 185,900,000 | 0 | 56,900,000 | 56,900,000 | 0 | 775,900,000 | 774,500,000 | 775,900,000 | 1,400,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cash portion of acquisition consideration | 4,554,000,000 | 4,554,000,000 | 0 | 88,000,000 | 88,000,000 | 88,000,000 | 0 | 12,800,000 | 12,800,000 | 12,800,000 | 0 | 56,900,000 | 56,900,000 | 56,900,000 | 0 | 757,000,000 | 757,000,000 | 757,000,000 | 0 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Working capital adjustment as part of acquisition consideration | 15,000,000 | 15,000,000 | 15,000,000 | 0 | 18,900,000 | 17,500,000 | 18,900,000 | 1,400,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Rated capacity (in tons) | 5,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in rated capacity (in tons) | 4,000,000 | 50,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ownership interest before acquisition | 26.80% | 4.00% | 4.00% | 26.50% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fair value of equity interest before acquisition | 39,700,000 | 39,700,000 | 38,000,000 | (1,700,000) | 38,000,000 | 1,700,000 | 27,400,000 | 27,400,000 | 27,400,000 | 0 | 4,900,000 | 4,900,000 | 4,900,000 | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gain on remeasurement of equity interest before acquisition | 0 | 0 | 40,700,000 | 47,000,000 | 25,100,000 | 13,600,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gain on remeasurement of equity interest before acquisition recorded in Accumulated other comprehensive income (loss) | 20,300,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Acquired intangible assets | 2,100,000 | 2,100,000 | 0 | 66,400,000 | 66,400,000 | 66,400,000 | 0 | 54,700,000 | 11,700,000 | 7,500,000 | 7,500,000 | 7,500,000 | 0 | 5,400,000 | 2,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Finite-lived intangible asset, estimated useful life | 15 years | 5 years | 30 years | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of shares acquired through business combination | 29,000,000 | 29,000,000 | 29,000,000 | 290,500,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of shares acquired | 12.40% | 48.00% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock exchanged per share acquired | 0.0201 | 0.0201 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of shares issued as acquisition consideration | 4,200,000 | 4,200,000 | 4,200,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fair value of equity portion of acquisition consideration | $ 173,100,000 | $ 173,100,000 | $ 173,100,000 | $ 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of shares owned | 27,400,000 | 27,400,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Noncontrolling interest, percent of ownership | 100.00% | 85.00% | 52.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of mineral deposits | 3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of mines (in number of facilities) | 2 | 1 | 2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Estimated coal reserve base | 62,000,000 | 59,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in coal reserve base | 67,000,000 | 166,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||