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Property, Plant And Equipment (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Detail) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2012
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Dec. 31, 2011
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| Property, Plant and Equipment, Gross | $ 12,477.8 | $ 11,881.5 |
| Allowance for depreciation and depletion | (1,595.7) | (1,356.9) |
| Total depreciable assets | 10,882.1 | 10,524.6 |
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Land Rights And Mineral Rights [Member]
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| Property, Plant and Equipment, Gross | 7,964.1 | 7,918.9 |
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Office And Information Technology [Member]
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| Property, Plant and Equipment, Gross | 63.9 | 67.0 |
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Buildings [Member]
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| Property, Plant and Equipment, Gross | 144.7 | 132.2 |
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Mining Equipment [Member]
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| Property, Plant and Equipment, Gross | 1,123.2 | 1,323.8 |
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Processing Equipment [Member]
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| Property, Plant and Equipment, Gross | 1,998.3 | 1,441.8 |
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Railroad Equipment [Member]
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| Property, Plant and Equipment, Gross | 241.5 | 164.3 |
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Electric Power Facilities [Member]
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| Property, Plant and Equipment, Gross | 58.2 | 57.9 |
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Port Facilities [Member]
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| Property, Plant and Equipment, Gross | 125.0 | 64.1 |
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Interest Capitalized During Construction [Member]
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| Property, Plant and Equipment, Gross | 27.6 | 22.5 |
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Land Improvements [Member]
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| Property, Plant and Equipment, Gross | 31.8 | 30.4 |
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Other [Member]
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| Property, Plant and Equipment, Gross | 32.5 | 43.2 |
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Construction In Progress [Member]
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| Property, Plant and Equipment, Gross | $ 667.0 | $ 615.4 |
| X | ||||||||||
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- Definition
The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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