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Commitments And Contingencies Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) (Manufactured Gas Plant Sites [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2014
Long-term Purchase Commitment [Line Items]  
Minimum range of estimated future costs $ 14
Maximum range of estimated future costs 33
Current and non-current environmental liabilities 21
IPL [Member]
  
Long-term Purchase Commitment [Line Items]  
Minimum range of estimated future costs 13
Maximum range of estimated future costs 31
Current and non-current environmental liabilities 19
WPL [Member]
  
Long-term Purchase Commitment [Line Items]  
Minimum range of estimated future costs 1
Maximum range of estimated future costs 2
Current and non-current environmental liabilities $ 2