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Income Taxes (Tables) | 9 Months Ended
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Sep. 30, 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 from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 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 | (11.0 | ) |  | (13.0 | ) |  | (30.0 | ) |  | (39.2 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (8.6 | ) |  | (18.7 | ) |  | (22.4 | ) |  | (0.7 | ) |  | (0.8 | )
Production tax credits | (6.7 | ) |  | (6.8 | ) |  | (8.7 | ) |  | (9.3 | ) |  | (6.0 | ) |  | (6.2 | )
Other items, net | 3.0 |  |  | 0.7 |  |  | 2.9 |  |  | 2.2 |  |  | 4.5 |  |  | — |
Overall income tax rate | 13.2 | % |  | 7.3 | % |  | (19.5 | %) |  | (33.7 | %) |  | 32.8 | % |  | 28.0 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | (10.6 | ) |  | (12.4 | ) |  | (28.2 | ) |  | (36.5 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (6.7 | ) |  | (17.9 | ) |  | (18.4 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.6 | ) |  | (6.6 | ) |  | (8.2 | ) |  | (8.8 | ) |  | (6.2 | ) |  | (6.2 | )
Other items, net | 3.7 |  |  | 2.9 |  |  | 3.5 |  |  | 3.2 |  |  | 4.5 |  |  | 3.0 |
Overall income tax rate | 14.4 | % |  | 12.2 | % |  | (15.8 | %) |  | (25.5 | %) |  | 32.7 | % |  | 31.1 | %
Summary Of Tax Credit Carryforwards | At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
|  |  | Alliant Energy |  | IPL |  | WPL
| Earliest Expiration Date |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets
Federal net operating losses | 2030 |  |  | $527 |  |  |  | $180 |  |  |  | $231 |  |  |  | $79 |  |  |  | $218 |  |  |  | $75 |
State net operating losses | 2018 |  | 731 |  |  | 37 |  |  | 183 |  |  | 9 |  |  | 126 |  |  | 6 |
Federal tax credits | 2022 |  | 227 |  |  | 224 |  |  | 80 |  |  | 78 |  |  | 89 |  |  | 87 |
|  |  |  |  |  | $441 |  |  |  |  |  | $166 |  |  |  |  |  | $168 |
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 from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 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 | (11.0 | ) |  | (13.0 | ) |  | (30.0 | ) |  | (39.2 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (8.6 | ) |  | (18.7 | ) |  | (22.4 | ) |  | (0.7 | ) |  | (0.8 | )
Production tax credits | (6.7 | ) |  | (6.8 | ) |  | (8.7 | ) |  | (9.3 | ) |  | (6.0 | ) |  | (6.2 | )
Other items, net | 3.0 |  |  | 0.7 |  |  | 2.9 |  |  | 2.2 |  |  | 4.5 |  |  | — |
Overall income tax rate | 13.2 | % |  | 7.3 | % |  | (19.5 | %) |  | (33.7 | %) |  | 32.8 | % |  | 28.0 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | (10.6 | ) |  | (12.4 | ) |  | (28.2 | ) |  | (36.5 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (6.7 | ) |  | (17.9 | ) |  | (18.4 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.6 | ) |  | (6.6 | ) |  | (8.2 | ) |  | (8.8 | ) |  | (6.2 | ) |  | (6.2 | )
Other items, net | 3.7 |  |  | 2.9 |  |  | 3.5 |  |  | 3.2 |  |  | 4.5 |  |  | 3.0 |
Overall income tax rate | 14.4 | % |  | 12.2 | % |  | (15.8 | %) |  | (25.5 | %) |  | 32.7 | % |  | 31.1 | %
Summary Of Tax Credit Carryforwards | At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
|  |  | Alliant Energy |  | IPL |  | WPL
| Earliest Expiration Date |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets
Federal net operating losses | 2030 |  |  | $527 |  |  |  | $180 |  |  |  | $231 |  |  |  | $79 |  |  |  | $218 |  |  |  | $75 |
State net operating losses | 2018 |  | 731 |  |  | 37 |  |  | 183 |  |  | 9 |  |  | 126 |  |  | 6 |
Federal tax credits | 2022 |  | 227 |  |  | 224 |  |  | 80 |  |  | 78 |  |  | 89 |  |  | 87 |
|  |  |  |  |  | $441 |  |  |  |  |  | $166 |  |  |  |  |  | $168 |
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 from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended September 30 | 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 | (11.0 | ) |  | (13.0 | ) |  | (30.0 | ) |  | (39.2 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (8.6 | ) |  | (18.7 | ) |  | (22.4 | ) |  | (0.7 | ) |  | (0.8 | )
Production tax credits | (6.7 | ) |  | (6.8 | ) |  | (8.7 | ) |  | (9.3 | ) |  | (6.0 | ) |  | (6.2 | )
Other items, net | 3.0 |  |  | 0.7 |  |  | 2.9 |  |  | 2.2 |  |  | 4.5 |  |  | — |
Overall income tax rate | 13.2 | % |  | 7.3 | % |  | (19.5 | %) |  | (33.7 | %) |  | 32.8 | % |  | 28.0 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | (10.6 | ) |  | (12.4 | ) |  | (28.2 | ) |  | (36.5 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.1 | ) |  | (6.7 | ) |  | (17.9 | ) |  | (18.4 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.6 | ) |  | (6.6 | ) |  | (8.2 | ) |  | (8.8 | ) |  | (6.2 | ) |  | (6.2 | )
Other items, net | 3.7 |  |  | 2.9 |  |  | 3.5 |  |  | 3.2 |  |  | 4.5 |  |  | 3.0 |
Overall income tax rate | 14.4 | % |  | 12.2 | % |  | (15.8 | %) |  | (25.5 | %) |  | 32.7 | % |  | 31.1 | %
Summary Of Tax Credit Carryforwards | At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):
|  |  | Alliant Energy |  | IPL |  | WPL
| Earliest Expiration Date |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets |  | Tax Carryforwards |  | Deferred Tax Assets
Federal net operating losses | 2030 |  |  | $527 |  |  |  | $180 |  |  |  | $231 |  |  |  | $79 |  |  |  | $218 |  |  |  | $75 |
State net operating losses | 2018 |  | 731 |  |  | 37 |  |  | 183 |  |  | 9 |  |  | 126 |  |  | 6 |
Federal tax credits | 2022 |  | 227 |  |  | 224 |  |  | 80 |  |  | 78 |  |  | 89 |  |  | 87 |
|  |  |  |  |  | $441 |  |  |  |  |  | $166 |  |  |  |  |  | $168 |

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