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Income Taxes (Tables) | 3 Months Ended
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Mar. 31, 2015
Income Taxes [Line Items] |
Schedule Of Effective Income Tax Rates | The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
IPL’s tax benefit riders | (9.9 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (31.2 | ) |  | — |  |  | — |
Production tax credits | (6.2 | ) |  | (6.7 | ) |  | (7.3 | ) |  | (8.3 | ) |  | (6.0 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (6.1 | ) |  | (5.3 | ) |  | (14.6 | ) |  | (12.4 | ) |  | (0.6 | ) |  | (1.0 | )
Other items, net | 4.3 |  |  | 4.6 |  |  | 4.4 |  |  | 4.7 |  |  | 4.6 |  |  | 4.8 |
Overall income tax rate | 17.1 | % |  | 15.7 | % |  | (7.7 | %) |  | (12.2 | %) |  | 33.0 | % |  | 32.4 | %
Production Tax Credits (Net Of State Tax Impacts) | For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):
| End of Production |  | Nameplate |  |
| Tax Credit Generation |  | Capacity in MW |  | 2015 |  | 2014
Cedar Ridge (WPL) | December 2018 |  | 68 |  |  |  | $1.2 |  |  |  | $1.2 |
Bent Tree - Phase I (WPL) | February 2021 |  | 201 |  |  | 3.9 |  |  | 4.2 |
Subtotal (WPL) |  |  |  |  | 5.1 |  |  | 5.4 |
Whispering Willow - East (IPL) | December 2019 |  | 200 |  |  | 4.3 |  |  | 4.6 |
|  |  |  |  |  | $9.4 |  |  |  | $10.0 |
Summary Of Tax Credit Carryforwards | At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $894 |  |  |  | $306 |  |  | 2029
State net operating losses | 853 |  |  | 44 |  |  | 2018
Federal tax credits | 214 |  |  | 210 |  |  | 2022
|  |  |  | $560 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $424 |  |  |  | $145 |  |  | 2029
State net operating losses | 260 |  |  | 13 |  |  | 2018
Federal tax credits | 73 |  |  | 72 |  |  | 2022
|  |  |  | $230 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $355 |  |  |  | $122 |  |  | 2029
State net operating losses | 166 |  |  | 8 |  |  | 2018
Federal tax credits | 82 |  |  | 80 |  |  | 2022
|  |  |  | $210 |  |  |
IPL [Member] |
Income Taxes [Line Items] |
Schedule Of Effective Income Tax Rates | The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
IPL’s tax benefit riders | (9.9 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (31.2 | ) |  | — |  |  | — |
Production tax credits | (6.2 | ) |  | (6.7 | ) |  | (7.3 | ) |  | (8.3 | ) |  | (6.0 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (6.1 | ) |  | (5.3 | ) |  | (14.6 | ) |  | (12.4 | ) |  | (0.6 | ) |  | (1.0 | )
Other items, net | 4.3 |  |  | 4.6 |  |  | 4.4 |  |  | 4.7 |  |  | 4.6 |  |  | 4.8 |
Overall income tax rate | 17.1 | % |  | 15.7 | % |  | (7.7 | %) |  | (12.2 | %) |  | 33.0 | % |  | 32.4 | %
Production Tax Credits (Net Of State Tax Impacts) | For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):
| End of Production |  | Nameplate |  |
| Tax Credit Generation |  | Capacity in MW |  | 2015 |  | 2014
Cedar Ridge (WPL) | December 2018 |  | 68 |  |  |  | $1.2 |  |  |  | $1.2 |
Bent Tree - Phase I (WPL) | February 2021 |  | 201 |  |  | 3.9 |  |  | 4.2 |
Subtotal (WPL) |  |  |  |  | 5.1 |  |  | 5.4 |
Whispering Willow - East (IPL) | December 2019 |  | 200 |  |  | 4.3 |  |  | 4.6 |
|  |  |  |  |  | $9.4 |  |  |  | $10.0 |
Summary Of Tax Credit Carryforwards | At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $894 |  |  |  | $306 |  |  | 2029
State net operating losses | 853 |  |  | 44 |  |  | 2018
Federal tax credits | 214 |  |  | 210 |  |  | 2022
|  |  |  | $560 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $424 |  |  |  | $145 |  |  | 2029
State net operating losses | 260 |  |  | 13 |  |  | 2018
Federal tax credits | 73 |  |  | 72 |  |  | 2022
|  |  |  | $230 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $355 |  |  |  | $122 |  |  | 2029
State net operating losses | 166 |  |  | 8 |  |  | 2018
Federal tax credits | 82 |  |  | 80 |  |  | 2022
|  |  |  | $210 |  |  |
WPL [Member] |
Income Taxes [Line Items] |
Schedule Of Effective Income Tax Rates | The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended March 31 | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
IPL’s tax benefit riders | (9.9 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (31.2 | ) |  | — |  |  | — |
Production tax credits | (6.2 | ) |  | (6.7 | ) |  | (7.3 | ) |  | (8.3 | ) |  | (6.0 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (6.1 | ) |  | (5.3 | ) |  | (14.6 | ) |  | (12.4 | ) |  | (0.6 | ) |  | (1.0 | )
Other items, net | 4.3 |  |  | 4.6 |  |  | 4.4 |  |  | 4.7 |  |  | 4.6 |  |  | 4.8 |
Overall income tax rate | 17.1 | % |  | 15.7 | % |  | (7.7 | %) |  | (12.2 | %) |  | 33.0 | % |  | 32.4 | %
Production Tax Credits (Net Of State Tax Impacts) | For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):
| End of Production |  | Nameplate |  |
| Tax Credit Generation |  | Capacity in MW |  | 2015 |  | 2014
Cedar Ridge (WPL) | December 2018 |  | 68 |  |  |  | $1.2 |  |  |  | $1.2 |
Bent Tree - Phase I (WPL) | February 2021 |  | 201 |  |  | 3.9 |  |  | 4.2 |
Subtotal (WPL) |  |  |  |  | 5.1 |  |  | 5.4 |
Whispering Willow - East (IPL) | December 2019 |  | 200 |  |  | 4.3 |  |  | 4.6 |
|  |  |  |  |  | $9.4 |  |  |  | $10.0 |
Summary Of Tax Credit Carryforwards | At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
Alliant Energy | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $894 |  |  |  | $306 |  |  | 2029
State net operating losses | 853 |  |  | 44 |  |  | 2018
Federal tax credits | 214 |  |  | 210 |  |  | 2022
|  |  |  | $560 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $424 |  |  |  | $145 |  |  | 2029
State net operating losses | 260 |  |  | 13 |  |  | 2018
Federal tax credits | 73 |  |  | 72 |  |  | 2022
|  |  |  | $230 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $355 |  |  |  | $122 |  |  | 2029
State net operating losses | 166 |  |  | 8 |  |  | 2018
Federal tax credits | 82 |  |  | 80 |  |  | 2022
|  |  |  | $210 |  |  |

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