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Commitments And Contingencies (Operating Expense Purchase Obligations) (Details) (USD $) In Millions, unless otherwise specified |  | 12 Months Ended | 1 Months Ended | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2013 Scenario, Forecast [Member] | Dec. 31, 2013 Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2014 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2015 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2016 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2017 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 2018 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] DAEC IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 Thereafter [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Purchased Power [Member] Scenario, Forecast [Member] | Jan. 31, 2013 IPL [Member] DAEC IPL [Member] MW | Dec. 31, 2013 IPL [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2007 IPL [Member] SO2 emission allowances [Member] | Dec. 31, 2013 IPL [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2014 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2015 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2016 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2017 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] 2018 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] DAEC [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] SO2 emission allowances [Member] Scenario, Forecast [Member] | Dec. 31, 2013 IPL [Member] Thereafter [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2014 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2014 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2014 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2014 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2014 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2015 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2015 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2015 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2015 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2015 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2016 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2016 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2016 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2016 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2016 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2017 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2017 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2017 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2017 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2017 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2018 [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2018 [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2018 [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2018 [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] 2018 [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Thereafter [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Thereafter [Member] Purchased Power [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Thereafter [Member] Natural Gas [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Thereafter [Member] Coal [Member] Scenario, Forecast [Member] | Dec. 31, 2013 WPL [Member] Thereafter [Member] Other [Member] Scenario, Forecast [Member] | Dec. 31, 2012 Alliant Energy and IPL [Member] SO2 emission allowances [Member] | Dec. 31, 2011 Alliant Energy and IPL [Member] SO2 emission allowances [Member]
Long-term Purchase Commitment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum future commitments |  | $ 2,583 | $ 1,915 | [1] | $ 1,657 | [1],[2] | $ 258 | [1] | $ 304 | $ 319 | [3] | $ 34 | [4] | $ 11 | [5] | $ 495 | $ 172 | [1] | $ 120 | [1],[2] | $ 52 | [1] | $ 187 | $ 128 | [3] | $ 0 | [4] | $ 8 | [5] | $ 353 | $ 192 | [1] | $ 119 | [1],[2] | $ 73 | [1] | $ 65 | $ 81 | [3] | $ 12 | [4] | $ 3 | [5] | $ 279 | $ 172 | [1] | $ 127 | [1],[2] | $ 45 | [1] | $ 34 | $ 59 | [3] | $ 14 | [4] | $ 0 | [5] | $ 230 | $ 182 | [1] | $ 138 | [1],[2] | $ 44 | [1] | $ 10 | $ 30 | [3] | $ 8 | [4] | $ 0 | [5] | $ 195 | $ 172 | [1] | $ 128 | [1],[2] | $ 44 | [1] | $ 2 | $ 21 | [3] | $ 0 | [4] | $ 0 | [5] | $ 1,031 | $ 1,025 | [1] | $ 1,025 | [1],[2] | $ 0 | [1] | $ 6 | $ 0 | [3] | $ 0 | [4] | $ 0 | [5] | $ 2,028 | $ 1,658 | [1] |  | $ 1,657 | [1],[2] | $ 1 | [1] | $ 191 | $ 139 | [3] | $ 34 | $ 34 | [4] | $ 6 | [5] | $ 317 | $ 120 | [1] | $ 120 | [1],[2] | $ 0 | [1] | $ 129 | $ 63 | [3] | $ 0 | [4] | $ 5 | [5] | $ 201 | $ 119 | [1] | $ 119 | [1],[2] | $ 0 | [1] | $ 37 | $ 32 | [3] | $ 12 | [4] | $ 1 | [5] | $ 184 | $ 128 | [1] | $ 127 | [1],[2] | $ 1 | [1] | $ 15 | $ 27 | [3] | $ 14 | [4] | $ 0 | [5] | $ 160 | $ 138 | [1] | $ 138 | [1],[2] | $ 0 | [1] | $ 3 | $ 11 | [3] | $ 8 | [4] | $ 0 | [5] | $ 135 | $ 128 | [1] | $ 128 | [1],[2] | $ 0 | [1] | $ 1 | $ 6 | [3] | $ 0 | [4] | $ 0 | [5] | $ 1,031 | $ 1,025 | [1] | $ 1,025 | [1],[2] | $ 0 | [1] | $ 6 | $ 0 | [3] | $ 0 | [4] | $ 0 | [5] | $ 552 | $ 257 | [1] | $ 113 | $ 180 | [3] | $ 2 | [5] | $ 177 | $ 52 | [1] | $ 58 | $ 65 | [3] | $ 2 | [5] | $ 150 | $ 73 | [1] | $ 28 | $ 49 | [3] | $ 0 | [5] | $ 95 | $ 44 | [1] | $ 19 | $ 32 | [3] | $ 0 | [5] | $ 70 | $ 44 | [1] | $ 7 | $ 19 | [3] | $ 0 | [5] | $ 60 | $ 44 | [1] | $ 1 | $ 15 | [3] | $ 0 | [5] | $ 0 | $ 0 | [1] | $ 0 | $ 0 | [3] | $ 0 | [5] | $ 34 | $ 34
Approved amount of electric power capacity (in megawatts) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 431 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Individual commitments incurred | $ 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Includes payments required by PPAs for capacity rights (Alliant Energy and IPL only) and minimum quantities of MWhs required to be purchased. Refer to Note 18 for additional information on purchased power transactions.
[2] | Includes commitments incurred under an existing PPA that expires February 2014 and a new PPA effective February 2014. The new PPA grants IPL rights to purchase 431 MWs of capacity and the resulting energy from DAEC for a term from the expiration of the existing PPA in February 2014 through December 31, 2025. If energy delivered under the new PPA is less than the targeted energy amount, an adjustment payment will be made to IPL, which will be reflected in IPL’s fuel adjustment clause.
[3] | 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 December 31, 2013 regarding expected future usage, which is subject to change.
[4] | Refer to Note 2 for discussion of $34 million of charges recognized by Alliant Energy and IPL in 2011 for forward contracts to purchase SO2 emission allowances.
[5] | Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2013.

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