Annual report pursuant to Section 13 and 15(d)

Pensions And Other Postretirement Benefits (Fair Value Of Plan Assets, Benefit Obligation And Funded Status) (Details)

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Pensions And Other Postretirement Benefits (Fair Value Of Plan Assets, Benefit Obligation And Funded Status) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Pension Benefits [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets $ 744.1 $ 734.3 $ 483.4
Benefit obligations (1,141.4) (1,022.3) (750.8)
Funded status (plan assets less benefit obligations) (397.3) (288.0)  
Pension Benefits [Member] | Salaried Employees [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 289.1 275.3  
Benefit obligations (419.3) (373.8)  
Funded status (plan assets less benefit obligations) (130.2) (98.5)  
Pension Benefits [Member] | Hourly Employees [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 451.8 456.7  
Benefit obligations (708.0) (635.3)  
Funded status (plan assets less benefit obligations) (256.2) (178.6)  
Pension Benefits [Member] | Mining Employees [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 3.2 2.3  
Benefit obligations (5.3) (4.4)  
Funded status (plan assets less benefit obligations) (2.1) (2.1)  
Pension Benefits [Member] | Supplemental Executive Retirement Plan SERP [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligations (8.8) (8.8)  
Funded status (plan assets less benefit obligations) (8.8) (8.8)  
Other Benefits [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 193.5 174.2 136.7
Benefit obligations (488.4) (440.2) (333.0)
Funded status (plan assets less benefit obligations) (294.9) (266.0)  
Other Benefits [Member] | Salaried Employees [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligations (70.7) (63.7)  
Funded status (plan assets less benefit obligations) (70.7) (63.7)  
Other Benefits [Member] | Hourly Employees [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets 193.5 174.2  
Benefit obligations (417.7) (376.5)  
Funded status (plan assets less benefit obligations) $ (224.2) $ (202.3)