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Commitments And Contingencies (Operating Expense Purchase Obligations) (Details)
$ in Millions
 6 Months Ended
Jun. 30, 2017
USD ($)
Commitments and Contingencies [Line Items]  
Minimum future commitments $ 2,270
Individual commitments incurred 1
IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 1,727
Individual commitments incurred 1
WPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 543
Individual commitments incurred 1
Purchased power [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 1,326 [1]
Purchased power [Member] | IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 1,231 [1]
Purchased power [Member] | WPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 95 [1]
Natural gas [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 774
Natural gas [Member] | IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 402
Natural gas [Member] | WPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 372
Coal [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 140 [2]
Coal [Member] | IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 66 [2]
Coal [Member] | WPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 74 [2]
Other [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 30 [3]
Other [Member] | IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments 28 [3]
Other [Member] | WPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum future commitments $ 2 [3]
[1] Includes payments required by purchased power agreements for capacity rights and minimum quantities of MWhs required to be purchased.
[2] Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2017 regarding expected future usage, which is subject to change.
[3] Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2017.