Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Benefit Obligations, Fair Value of Plan Assets, and Net Funded Status) (Details)

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PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Benefit Obligations, Fair Value of Plan Assets, and Net Funded Status) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — beginning of year $ 192.2 $ 186.0  
Employer contributions 39.0 37.4  
Fair value of plan assets — end of year 200.5 192.2  
Funded status at December 31:      
Fair value of plan assets 200.5 192.2  
Amounts recognized in Statements of Financial Position:      
Noncurrent liabilities (618.3) (665.8)  
Pension Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — beginning of year 1,141.4 1,022.3  
Service cost (excluding expenses) 32.0 23.6 18.5
Interest cost 48.4 51.4 52.9
Plan amendments 2.8 0  
Actuarial loss 84.3 117.3  
Benefits paid (71.0) (67.3)  
Participant contributions 0 0  
Federal subsidy on benefits paid 0 0  
Exchange rate gain 6.4 (5.9)  
Benefit obligations — end of year 1,244.3 1,141.4 1,022.3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — beginning of year 744.1 734.3  
Actual return on plan assets 92.5 10.8 87.1
Participant contributions 0 0  
Employer contributions 67.7 70.1  
Benefits paid (71.0) (67.3)  
Exchange rate gain 5.4 (3.8)  
Fair value of plan assets — end of year 838.7 744.1 734.3
Funded status at December 31:      
Fair value of plan assets 838.7 744.1 734.3
Benefit obligations (1,244.3) (1,141.4) (1,022.3)
Underfunded status of plan (405.6) (397.3)  
Amount recognized at December 31 (405.6) (397.3)  
Amounts recognized in Statements of Financial Position:      
Current liabilities (1.8) (2.6)  
Noncurrent liabilities (403.8) (394.7)  
Net amount recognized (405.6) (397.3)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 429.2 409.1  
Prior service cost 17.2 18.8  
Transition asset 0 0  
Net amount recognized 446.4 427.9  
The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013:      
Net actuarial loss 30.3    
Prior service cost 3.0    
Net amount recognized 33.3    
Other Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — beginning of year 488.4 440.2  
Service cost (excluding expenses) 14.7 11.1 7.5
Interest cost 20.6 22.3 22.0
Plan amendments (58.3) 0  
Actuarial loss 11.3 36.5  
Benefits paid (26.9) (25.5)  
Participant contributions 4.6 4.6  
Federal subsidy on benefits paid 0.8 0.9  
Exchange rate gain 4.6 (1.7)  
Benefit obligations — end of year 459.8 488.4 440.2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — beginning of year 193.5 174.2  
Actual return on plan assets 26.1 1.9 20.1
Participant contributions 1.7 1.6  
Employer contributions 23.3 23.2  
Benefits paid (7.6) (7.4)  
Exchange rate gain 0 0  
Fair value of plan assets — end of year 237.0 193.5 174.2
Funded status at December 31:      
Fair value of plan assets 237.0 193.5 174.2
Benefit obligations (459.8) (488.4) (440.2)
Underfunded status of plan (222.8) (294.9)  
Amount recognized at December 31 (222.8) (294.9)  
Amounts recognized in Statements of Financial Position:      
Current liabilities (8.3) (23.8)  
Noncurrent liabilities (214.5) (271.1)  
Net amount recognized (222.8) (294.9)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 176.8 182.9  
Prior service cost (48.8) 8.1  
Transition asset 0 (3.0)  
Net amount recognized 128.0 188.0  
The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013:      
Net actuarial loss 11.1    
Prior service cost (3.6)    
Net amount recognized 7.5    
Salaried Employees [Member] | Pension Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 464.4 419.3  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 328.2 289.1  
Funded status at December 31:      
Fair value of plan assets 328.2 289.1  
Benefit obligations (464.4) (419.3)  
Underfunded status of plan (136.2) (130.2)  
Salaried Employees [Member] | Other Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 72.6 70.7  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 0 0  
Funded status at December 31:      
Fair value of plan assets 0 0  
Benefit obligations (72.6) (70.7)  
Underfunded status of plan (72.6) (70.7)  
Hourly Employees [Member] | Pension Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 764.8 708.0  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 506.4 451.8  
Funded status at December 31:      
Fair value of plan assets 506.4 451.8  
Benefit obligations (764.8) (708.0)  
Underfunded status of plan (258.4) (256.2)  
Hourly Employees [Member] | Other Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 387.2 417.7  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 237.0 193.5  
Funded status at December 31:      
Fair value of plan assets 237.0 193.5  
Benefit obligations (387.2) (417.7)  
Underfunded status of plan (150.2) (224.2)  
Mining Employees [Member] | Pension Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 6.4 5.3  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 4.1 3.2  
Funded status at December 31:      
Fair value of plan assets 4.1 3.2  
Benefit obligations (6.4) (5.3)  
Underfunded status of plan (2.3) (2.1)  
Supplemental Executive Retirement Plan S E R P [Member] | Pension Benefits [Member]
     
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligations — end of year 8.7 8.8  
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets — end of year 0 0  
Funded status at December 31:      
Fair value of plan assets 0 0  
Benefit obligations (8.7) (8.8)  
Underfunded status of plan $ (8.7) $ (8.8)