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Commitments And Contingencies (Operating Expense Purchase Obligations) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2016 USD ($)
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | $ 2,400 |
Individual commitments incurred | 1 |
Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1,418 | [1]
Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 771 |
Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 177 | [2]
Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 34 | [3]
2017 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 529 |
2017 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 185 | [1]
2017 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 223 |
2017 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 105 | [2]
2017 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 16 | [3]
2018 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 389 |
2018 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 189 | [1]
2018 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 142 |
2018 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 54 | [2]
2018 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 4 | [3]
2019 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 297 |
2019 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 159 | [1]
2019 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 115 |
2019 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 18 | [2]
2019 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 5 | [3]
2020 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 237 |
2020 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 137 | [1]
2020 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 98 |
2020 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
2020 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 2 | [3]
2021 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 220 |
2021 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 149 | [1]
2021 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 69 |
2021 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
2021 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 2 | [3]
Thereafter [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 728 |
Thereafter [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 599 | [1]
Thereafter [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 124 |
Thereafter [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
Thereafter [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 5 | [3]
IPL [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1,774 |
IPL [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1,298 | [1]
IPL [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 382 |
IPL [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 77 | [2]
IPL [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 17 | [3]
IPL [Member] | 2017 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 322 |
IPL [Member] | 2017 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 138 | [1]
IPL [Member] | 2017 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 120 |
IPL [Member] | 2017 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 49 | [2]
IPL [Member] | 2017 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 15 | [3]
IPL [Member] | 2018 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 225 |
IPL [Member] | 2018 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 131 | [1]
IPL [Member] | 2018 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 74 |
IPL [Member] | 2018 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 19 | [2]
IPL [Member] | 2018 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1 | [3]
IPL [Member] | 2019 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 209 |
IPL [Member] | 2019 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 144 | [1]
IPL [Member] | 2019 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 55 |
IPL [Member] | 2019 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 9 | [2]
IPL [Member] | 2019 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1 | [3]
IPL [Member] | 2020 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 176 |
IPL [Member] | 2020 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 137 | [1]
IPL [Member] | 2020 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 39 |
IPL [Member] | 2020 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
IPL [Member] | 2020 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
IPL [Member] | 2021 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 172 |
IPL [Member] | 2021 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 149 | [1]
IPL [Member] | 2021 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 23 |
IPL [Member] | 2021 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
IPL [Member] | 2021 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
IPL [Member] | Thereafter [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 670 |
IPL [Member] | Thereafter [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 599 | [1]
IPL [Member] | Thereafter [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 71 |
IPL [Member] | Thereafter [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
IPL [Member] | Thereafter [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
WPL [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 611 |
WPL [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 120 | [1]
WPL [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 389 |
WPL [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 100 | [2]
WPL [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 2 | [3]
WPL [Member] | 2017 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 206 |
WPL [Member] | 2017 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 47 | [1]
WPL [Member] | 2017 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 103 |
WPL [Member] | 2017 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 56 | [2]
WPL [Member] | 2017 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
WPL [Member] | 2018 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 162 |
WPL [Member] | 2018 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 58 | [1]
WPL [Member] | 2018 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 68 |
WPL [Member] | 2018 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 35 | [2]
WPL [Member] | 2018 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1 | [3]
WPL [Member] | 2019 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 85 |
WPL [Member] | 2019 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 15 | [1]
WPL [Member] | 2019 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 60 |
WPL [Member] | 2019 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 9 | [2]
WPL [Member] | 2019 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 1 | [3]
WPL [Member] | 2020 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 59 |
WPL [Member] | 2020 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [1]
WPL [Member] | 2020 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 59 |
WPL [Member] | 2020 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
WPL [Member] | 2020 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
WPL [Member] | 2021 [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 46 |
WPL [Member] | 2021 [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [1]
WPL [Member] | 2021 [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 46 |
WPL [Member] | 2021 [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
WPL [Member] | 2021 [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [3]
WPL [Member] | Thereafter [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 53 |
WPL [Member] | Thereafter [Member] | Purchased Power [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [1]
WPL [Member] | Thereafter [Member] | Natural Gas [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 53 |
WPL [Member] | Thereafter [Member] | Coal [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | 0 | [2]
WPL [Member] | Thereafter [Member] | Other [Member] |  |
Long-term Purchase Commitment [Line Items] |  |
Minimum future commitments | $ 0 | [3]
[1] | Includes payments required by PPAs 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 December 31, 2016 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 December 31, 2016.

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