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Income Taxes (Tables) | 6 Months Ended
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Jun. 30, 2019
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 taxes by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 6.5 |  |  | 8.3 |  |  | 7.0 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.5 | ) |  | (5.4 | ) |  | (13.2 | ) |  | (5.3 | ) |  | (4.2 | ) |  | (6.8 | )
Effect of rate-making on property-related differences | (6.2 | ) |  | (6.7 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (2.7 | ) |  | (2.7 | )
Amortization of excess deferred taxes | (1.3 | ) |  | (0.4 | ) |  | (0.4 | ) |  | — |  |  | (2.3 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.1 | ) |  | (1.4 | ) |  | (4.3 | ) |  | — |  |  | — |
Other items, net | (1.5 | ) |  | (1.2 | ) |  | (0.4 | ) |  | (2.8 | ) |  | (2.5 | ) |  | (4.1 | )
Overall income tax rate | 10.3 | % |  | 11.7 | % |  | 3.8 | % |  | 4.1 | % |  | 15.5 | % |  | 13.5 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.2 |  |  | 7.1 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.9 | ) |  | (5.5 | ) |  | (13.6 | ) |  | (5.3 | ) |  | (4.6 | ) |  | (6.7 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (7.2 | ) |  | (9.6 | ) |  | (12.4 | ) |  | (2.4 | ) |  | (2.5 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.4 | ) |  | (0.3 | ) |  | — |  |  | (1.8 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.4 | ) |  | (4.5 | ) |  | — |  |  | — |
Other items, net | (1.0 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.5 | ) |  | (1.2 | ) |  | (1.9 | )
Overall income tax rate | 10.5 | % |  | 11.8 | % |  | 3.7 | % |  | 5.0 | % |  | 17.2 | % |  | 16.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2031-2037 |  |  | $760 |  |  |  | $550 |  |  |  | $122 |
State net operating losses | 2019-2039 |  | 764 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 325 |  |  | 152 |  |  | 154 |
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 taxes by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 6.5 |  |  | 8.3 |  |  | 7.0 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.5 | ) |  | (5.4 | ) |  | (13.2 | ) |  | (5.3 | ) |  | (4.2 | ) |  | (6.8 | )
Effect of rate-making on property-related differences | (6.2 | ) |  | (6.7 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (2.7 | ) |  | (2.7 | )
Amortization of excess deferred taxes | (1.3 | ) |  | (0.4 | ) |  | (0.4 | ) |  | — |  |  | (2.3 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.1 | ) |  | (1.4 | ) |  | (4.3 | ) |  | — |  |  | — |
Other items, net | (1.5 | ) |  | (1.2 | ) |  | (0.4 | ) |  | (2.8 | ) |  | (2.5 | ) |  | (4.1 | )
Overall income tax rate | 10.3 | % |  | 11.7 | % |  | 3.8 | % |  | 4.1 | % |  | 15.5 | % |  | 13.5 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.2 |  |  | 7.1 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.9 | ) |  | (5.5 | ) |  | (13.6 | ) |  | (5.3 | ) |  | (4.6 | ) |  | (6.7 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (7.2 | ) |  | (9.6 | ) |  | (12.4 | ) |  | (2.4 | ) |  | (2.5 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.4 | ) |  | (0.3 | ) |  | — |  |  | (1.8 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.4 | ) |  | (4.5 | ) |  | — |  |  | — |
Other items, net | (1.0 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.5 | ) |  | (1.2 | ) |  | (1.9 | )
Overall income tax rate | 10.5 | % |  | 11.8 | % |  | 3.7 | % |  | 5.0 | % |  | 17.2 | % |  | 16.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2031-2037 |  |  | $760 |  |  |  | $550 |  |  |  | $122 |
State net operating losses | 2019-2039 |  | 764 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 325 |  |  | 152 |  |  | 154 |
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 taxes by income before income taxes.
| Alliant Energy |  | IPL |  | WPL
Three Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 6.5 |  |  | 8.3 |  |  | 7.0 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.5 | ) |  | (5.4 | ) |  | (13.2 | ) |  | (5.3 | ) |  | (4.2 | ) |  | (6.8 | )
Effect of rate-making on property-related differences | (6.2 | ) |  | (6.7 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (2.7 | ) |  | (2.7 | )
Amortization of excess deferred taxes | (1.3 | ) |  | (0.4 | ) |  | (0.4 | ) |  | — |  |  | (2.3 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.1 | ) |  | (1.4 | ) |  | (4.3 | ) |  | — |  |  | — |
Other items, net | (1.5 | ) |  | (1.2 | ) |  | (0.4 | ) |  | (2.8 | ) |  | (2.5 | ) |  | (4.1 | )
Overall income tax rate | 10.3 | % |  | 11.7 | % |  | 3.8 | % |  | 4.1 | % |  | 15.5 | % |  | 13.5 | %
| Alliant Energy |  | IPL |  | WPL
Six Months Ended June 30 | 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Statutory federal income tax rate | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | % |  | 21.0 | %
State income taxes, net of federal benefits | 7.2 |  |  | 7.1 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (8.9 | ) |  | (5.5 | ) |  | (13.6 | ) |  | (5.3 | ) |  | (4.6 | ) |  | (6.7 | )
Effect of rate-making on property-related differences | (6.0 | ) |  | (7.2 | ) |  | (9.6 | ) |  | (12.4 | ) |  | (2.4 | ) |  | (2.5 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.4 | ) |  | (0.3 | ) |  | — |  |  | (1.8 | ) |  | (0.1 | )
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.4 | ) |  | (4.5 | ) |  | — |  |  | — |
Other items, net | (1.0 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.5 | ) |  | (1.2 | ) |  | (1.9 | )
Overall income tax rate | 10.5 | % |  | 11.8 | % |  | 3.7 | % |  | 5.0 | % |  | 17.2 | % |  | 16.0 | %
Summary Of Tax Credit Carryforwards | At June 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2031-2037 |  |  | $760 |  |  |  | $550 |  |  |  | $122 |
State net operating losses | 2019-2039 |  | 764 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 325 |  |  | 152 |  |  | 154 |

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