Quarterly report pursuant to Section 13 or 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
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Dec. 31, 2010
Dec. 31, 2009
Increase in balance of Goodwill $ 1,026.8   $ 1,026.8   $ 111.9 [1]  
Goodwill 1,227.3   1,227.3   196.5 [1] 74.6 [1]
Amortization expense relating to intangible assets 4.7 4.3 9.6 8.3    
Revenues 1,705.0 1,116.2 2,838.0 1,787.7    
Upper Limit [Member]
            
Below-market sales contracts life (in years) 8.5   8.5      
Lower Limit [Member]
            
Below-market sales contracts life (in years) 3.5   3.5      
Below Market Sales Contracts [Member]
            
Revenues $ 16.6 $ 11.8 $ 23.7 $ 11.8    
[1] Represents a 12-month rollforward of our goodwill by reportable unit at December 31, 2010.