XML 78 R30.htm IDEA: XBRL DOCUMENT v2.3.0.15
Short-Term Debt (Tables)
9 Months Ended
Sep. 30, 2011
Short-Term Debt 
Credit Facilities

At Sep. 30, 2011

    Alliant Energy
(Consolidated)		     Parent
Company		     IPL      WPL  

Commercial paper:

          

Amount outstanding

    $ 22.1      $ 22.1      $ —         $ —     

Remaining maturity

      3 days        3 days        N/A         N/A   

Interest rates

      0.38 %      0.38 %      N/A         N/A   

Available credit facility capacity

    $ 600.9      $ 73.8      $ 287.5       $ 239.6   
Other Short-Term Borrowings
     Alliant Energy     IPL     WPL  
     2011     2010     2011     2010     2011     2010  

Three months ended Sep. 30

             

Maximum amount of total short-term debt outstanding
(based on daily outstanding balances)

    $ 22.1      $ —        $ 18.0      $ 11.3      $ —        $ —     

Average amount of total short-term debt outstanding
(based on daily outstanding balances)

    $ 2.6      $ —        $ 1.7      $ 0.3      $ —        $ —     

Weighted average interest rates—total short-term debt

      0.37 %      N/A        0.34 %      0.27 %      N/A        N/A   

Nine months ended Sep. 30

             

Maximum amount of total short-term debt outstanding
(based on daily outstanding balances)

    $ 96.5      $ 350.3      $ 54.4      $ 219.1      $ 96.5      $ 170.2   

Average amount of total short-term debt outstanding
(based on daily outstanding balances)

    $ 28.7      $ 118.2      $ 7.1      $ 83.2      $ 23.0      $ 44.1   

Weighted average interest rates—total short-term debt

      0.31 %      0.32 %      0.32 %      0.34 %      0.31 %      0.29 %