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Income Taxes (Tables) | 6 Months Ended
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Jun. 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 June 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 | ) |  | (11.9 | ) |  | (25.3 | ) |  | (36.6 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.4 | ) |  | (4.8 | ) |  | (22.3 | ) |  | (14.4 | ) |  | (0.7 | ) |  | (0.2 | )
Production tax credits | (6.5 | ) |  | (6.1 | ) |  | (7.2 | ) |  | (8.0 | ) |  | (6.7 | ) |  | (5.8 | )
Other items, net | 4.1 |  |  | 4.8 |  |  | 4.1 |  |  | 4.6 |  |  | 4.6 |  |  | 5.0 |
Overall income tax rate | 13.6 | % |  | 17.0 | % |  | (15.7 | %) |  | (19.4 | %) |  | 32.2 | % |  | 34.0 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 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 | (10.2 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (32.8 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.0 | ) |  | (5.1 | ) |  | (16.6 | ) |  | (13.0 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.4 | ) |  | (6.5 | ) |  | (7.2 | ) |  | (8.2 | ) |  | (6.4 | ) |  | (6.2 | )
Other items, net | 4.3 |  |  | 4.7 |  |  | 4.2 |  |  | 4.6 |  |  | 4.7 |  |  | 4.9 |
Overall income tax rate | 15.7 | % |  | 16.2 | % |  | (9.8 | %) |  | (14.4 | %) |  | 32.7 | % |  | 33.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 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 |  | $845 |  |  |  | $290 |  |  | 2029
State net operating losses | 860 |  |  | 44 |  |  | 2018
Federal tax credits | 222 |  |  | 218 |  |  | 2022
|  |  |  | $552 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $396 |  |  |  | $136 |  |  | 2029
State net operating losses | 265 |  |  | 14 |  |  | 2018
Federal tax credits | 77 |  |  | 75 |  |  | 2022
|  |  |  | $225 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $342 |  |  |  | $117 |  |  | 2029
State net operating losses | 170 |  |  | 8 |  |  | 2018
Federal tax credits | 86 |  |  | 85 |  |  | 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 from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended June 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 | ) |  | (11.9 | ) |  | (25.3 | ) |  | (36.6 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.4 | ) |  | (4.8 | ) |  | (22.3 | ) |  | (14.4 | ) |  | (0.7 | ) |  | (0.2 | )
Production tax credits | (6.5 | ) |  | (6.1 | ) |  | (7.2 | ) |  | (8.0 | ) |  | (6.7 | ) |  | (5.8 | )
Other items, net | 4.1 |  |  | 4.8 |  |  | 4.1 |  |  | 4.6 |  |  | 4.6 |  |  | 5.0 |
Overall income tax rate | 13.6 | % |  | 17.0 | % |  | (15.7 | %) |  | (19.4 | %) |  | 32.2 | % |  | 34.0 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 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 | (10.2 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (32.8 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.0 | ) |  | (5.1 | ) |  | (16.6 | ) |  | (13.0 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.4 | ) |  | (6.5 | ) |  | (7.2 | ) |  | (8.2 | ) |  | (6.4 | ) |  | (6.2 | )
Other items, net | 4.3 |  |  | 4.7 |  |  | 4.2 |  |  | 4.6 |  |  | 4.7 |  |  | 4.9 |
Overall income tax rate | 15.7 | % |  | 16.2 | % |  | (9.8 | %) |  | (14.4 | %) |  | 32.7 | % |  | 33.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 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 |  | $845 |  |  |  | $290 |  |  | 2029
State net operating losses | 860 |  |  | 44 |  |  | 2018
Federal tax credits | 222 |  |  | 218 |  |  | 2022
|  |  |  | $552 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $396 |  |  |  | $136 |  |  | 2029
State net operating losses | 265 |  |  | 14 |  |  | 2018
Federal tax credits | 77 |  |  | 75 |  |  | 2022
|  |  |  | $225 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $342 |  |  |  | $117 |  |  | 2029
State net operating losses | 170 |  |  | 8 |  |  | 2018
Federal tax credits | 86 |  |  | 85 |  |  | 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 from continuing operations before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended June 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 | ) |  | (11.9 | ) |  | (25.3 | ) |  | (36.6 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.4 | ) |  | (4.8 | ) |  | (22.3 | ) |  | (14.4 | ) |  | (0.7 | ) |  | (0.2 | )
Production tax credits | (6.5 | ) |  | (6.1 | ) |  | (7.2 | ) |  | (8.0 | ) |  | (6.7 | ) |  | (5.8 | )
Other items, net | 4.1 |  |  | 4.8 |  |  | 4.1 |  |  | 4.6 |  |  | 4.6 |  |  | 5.0 |
Overall income tax rate | 13.6 | % |  | 17.0 | % |  | (15.7 | %) |  | (19.4 | %) |  | 32.2 | % |  | 34.0 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 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 | (10.2 | ) |  | (11.9 | ) |  | (25.2 | ) |  | (32.8 | ) |  | — |  |  | — |
Effect of rate-making on property-related differences | (7.0 | ) |  | (5.1 | ) |  | (16.6 | ) |  | (13.0 | ) |  | (0.6 | ) |  | (0.7 | )
Production tax credits | (6.4 | ) |  | (6.5 | ) |  | (7.2 | ) |  | (8.2 | ) |  | (6.4 | ) |  | (6.2 | )
Other items, net | 4.3 |  |  | 4.7 |  |  | 4.2 |  |  | 4.6 |  |  | 4.7 |  |  | 4.9 |
Overall income tax rate | 15.7 | % |  | 16.2 | % |  | (9.8 | %) |  | (14.4 | %) |  | 32.7 | % |  | 33.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 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 |  | $845 |  |  |  | $290 |  |  | 2029
State net operating losses | 860 |  |  | 44 |  |  | 2018
Federal tax credits | 222 |  |  | 218 |  |  | 2022
|  |  |  | $552 |  |  |
IPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $396 |  |  |  | $136 |  |  | 2029
State net operating losses | 265 |  |  | 14 |  |  | 2018
Federal tax credits | 77 |  |  | 75 |  |  | 2022
|  |  |  | $225 |  |  |
WPL | Tax Carryforwards |  | Deferred Tax Assets |  | Earliest Expiration Date
Federal net operating losses |  | $342 |  |  |  | $117 |  |  | 2029
State net operating losses | 170 |  |  | 8 |  |  | 2018
Federal tax credits | 86 |  |  | 85 |  |  | 2022
|  |  |  | $210 |  |  |

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