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Pension and Other Postretirement Benefits (Tables)
3 Months Ended
Mar. 31, 2012
Pension and Other Postretirement Benefits  
Schedule of net periodic benefit cost

 

 

 
  Three months ended
March 31,
 
 
  2012   2011  
 
  (in millions)
 

Pension Plans

             

Service cost for benefits earned during the period

  $ 3.2   $ 3.0  

Interest cost on projected benefit obligation

    8.6     9.1  

Expected return on plan assets

    (8.6 )   (8.7 )

Amortization of actuarial loss

    2.6     1.5  
           

Net periodic benefit cost

  $ 5.8   $ 4.9  
           

Retiree Medical

             

Service cost for benefits earned during the period

  $ 0.8   $ 0.7  

Interest cost on projected benefit obligation

    1.0     1.0  

Amortization of transition obligation

    0.1     0.1  

Amortization of actuarial loss

    0.3     0.2  
           

Net periodic benefit cost

  $ 2.2   $ 2.0