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Commitments And Contingencies (Tables)
 3 Months Ended
Mar. 31, 2012
Commitments And Contingencies [Abstract]  
Operating Expense Purchase Obligations
Alliant Energy      IPL      WPL  

Purchased power (a):

         

Duane Arnold Energy Center (DAEC) (IPL)

    $ 364       $ 364       $ —     

Kewaunee Nuclear Power Plant (Kewaunee) (WPL)

      131         —           131   

Other

      41         9         32   
  

 

 

     

 

 

     

 

 

  
     536         373         163   

Natural gas

      255         120         135   

Coal (b)

      274         88         61   

Sulfur dioxide (SO2) emission allowances

      34         34         —     

Other (c)

      41         19         22   
  

 

 

     

 

 

     

 

 

  
   $ 1,140       $ 634       $ 381   
  

 

 

     

 

 

     

 

 

  

 

  (a) Includes payments required by purchased power agreements (PPAs) for capacity rights and minimum quantities of MWhs required to be purchased. Excludes contracts that are considered operating leases.
  (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments of $125 million that have not been directly assigned to IPL and WPL since the specific needs of each utility were not yet known as of March 31, 2012.
  (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2012.