Annual report pursuant to Section 13 and 15(d)

Goodwill And Other Intangible Assets And Liabilities (Narrative) (Details)

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Goodwill And Other Intangible Assets And Liabilities (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended 12 Months Ended 12 Months Ended 3 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2011
North American Coal [Member]
Dec. 31, 2010
North American Coal [Member]
Dec. 31, 2009
North American Coal [Member]
Dec. 31, 2010
Other [Member]
Dec. 31, 2011
Other [Member]
Dec. 31, 2011
Lower Limit [Member]
Dec. 31, 2011
Upper Limit [Member]
Dec. 31, 2011
Below-Market Sales Contracts [Member]
Dec. 31, 2010
Below-Market Sales Contracts [Member]
Dec. 31, 2009
Below-Market Sales Contracts [Member]
Dec. 31, 2011
Consolidated Thompson [Member]
Dec. 31, 2011
CLCC [Member]
Arising in business combinations $ 983.4 $ 111.9   $ (0.1) $ 27.9   $ 80.9                
Goodwill 1,152.1 196.5 74.6   27.9    80.9 80.9           983.5  
Goodwill, Impairment Loss 27.8     27.8                      27.8
Amortization expense relating to intangible assets 17.7 18.8 8.2                        
Below-market sales contracts life (in years)                 3.5 8.5          
Product $ 6,551.7 $ 4,416.8 $ 2,216.2               $ 57.0 $ 62.4 $ 30.3