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Income Taxes (Tables) | 9 Months Ended
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Sep. 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 September 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 | 7.0 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.3 | ) |  | (5.4 | ) |  | (14.7 | ) |  | (5.5 | ) |  | (4.4 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (5.6 | ) |  | (6.3 | ) |  | (9.0 | ) |  | (11.5 | ) |  | (2.8 | ) |  | (2.1 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (1.8 | ) |  | (5.7 | ) |  | 1.3 |  |  | (10.2 | ) |  | 0.4 |  |  | — |
IPL’s tax benefit riders | (0.8 | ) |  | (2.3 | ) |  | (1.5 | ) |  | (4.8 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | )
Other items, net | (0.2 | ) |  | (0.3 | ) |  | (0.3 | ) |  | (0.6 | ) |  | (0.2 | ) |  | (0.4 | )
Overall income tax rate | 9.2 | % |  | 5.3 | % |  | 4.6 | % |  | (4.8 | %) |  | 18.5 | % |  | 11.8 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 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 | 7.1 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.1 | ) |  | (5.4 | ) |  | (14.3 | ) |  | (5.4 | ) |  | (4.5 | ) |  | (6.6 | )
Effect of rate-making on property-related differences | (5.7 | ) |  | (6.7 | ) |  | (9.3 | ) |  | (12.0 | ) |  | (2.6 | ) |  | (2.3 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.3 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (0.7 | ) |  | (2.6 | ) |  | 0.6 |  |  | (5.4 | ) |  | (0.3 | ) |  | — |
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.5 | ) |  | (4.6 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | )
Other items, net | (1.0 | ) |  | (0.7 | ) |  | (0.1 | ) |  | (1.0 | ) |  | (0.4 | ) |  | (1.2 | )
Overall income tax rate | 9.8 | % |  | 8.8 | % |  | 4.2 | % |  | (0.2 | %) |  | 17.7 | % |  | 14.2 | %
Summary Of Tax Credit Carryforwards | At September 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 |  |  | $611 |  |  |  | $522 |  |  |  | $41 |
State net operating losses | 2019-2039 |  | 677 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 337 |  |  | 162 |  |  | 156 |
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 September 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 | 7.0 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.3 | ) |  | (5.4 | ) |  | (14.7 | ) |  | (5.5 | ) |  | (4.4 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (5.6 | ) |  | (6.3 | ) |  | (9.0 | ) |  | (11.5 | ) |  | (2.8 | ) |  | (2.1 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (1.8 | ) |  | (5.7 | ) |  | 1.3 |  |  | (10.2 | ) |  | 0.4 |  |  | — |
IPL’s tax benefit riders | (0.8 | ) |  | (2.3 | ) |  | (1.5 | ) |  | (4.8 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | )
Other items, net | (0.2 | ) |  | (0.3 | ) |  | (0.3 | ) |  | (0.6 | ) |  | (0.2 | ) |  | (0.4 | )
Overall income tax rate | 9.2 | % |  | 5.3 | % |  | 4.6 | % |  | (4.8 | %) |  | 18.5 | % |  | 11.8 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 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 | 7.1 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.1 | ) |  | (5.4 | ) |  | (14.3 | ) |  | (5.4 | ) |  | (4.5 | ) |  | (6.6 | )
Effect of rate-making on property-related differences | (5.7 | ) |  | (6.7 | ) |  | (9.3 | ) |  | (12.0 | ) |  | (2.6 | ) |  | (2.3 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.3 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (0.7 | ) |  | (2.6 | ) |  | 0.6 |  |  | (5.4 | ) |  | (0.3 | ) |  | — |
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.5 | ) |  | (4.6 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | )
Other items, net | (1.0 | ) |  | (0.7 | ) |  | (0.1 | ) |  | (1.0 | ) |  | (0.4 | ) |  | (1.2 | )
Overall income tax rate | 9.8 | % |  | 8.8 | % |  | 4.2 | % |  | (0.2 | %) |  | 17.7 | % |  | 14.2 | %
Summary Of Tax Credit Carryforwards | At September 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 |  |  | $611 |  |  |  | $522 |  |  |  | $41 |
State net operating losses | 2019-2039 |  | 677 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 337 |  |  | 162 |  |  | 156 |
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 September 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 | 7.0 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.3 | ) |  | (5.4 | ) |  | (14.7 | ) |  | (5.5 | ) |  | (4.4 | ) |  | (6.4 | )
Effect of rate-making on property-related differences | (5.6 | ) |  | (6.3 | ) |  | (9.0 | ) |  | (11.5 | ) |  | (2.8 | ) |  | (2.1 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (1.8 | ) |  | (5.7 | ) |  | 1.3 |  |  | (10.2 | ) |  | 0.4 |  |  | — |
IPL’s tax benefit riders | (0.8 | ) |  | (2.3 | ) |  | (1.5 | ) |  | (4.8 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | )
Other items, net | (0.2 | ) |  | (0.3 | ) |  | (0.3 | ) |  | (0.6 | ) |  | (0.2 | ) |  | (0.4 | )
Overall income tax rate | 9.2 | % |  | 5.3 | % |  | 4.6 | % |  | (4.8 | %) |  | 18.5 | % |  | 11.8 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 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 | 7.1 |  |  | 6.9 |  |  | 8.1 |  |  | 7.7 |  |  | 6.2 |  |  | 6.2 |
Production tax credits | (9.1 | ) |  | (5.4 | ) |  | (14.3 | ) |  | (5.4 | ) |  | (4.5 | ) |  | (6.6 | )
Effect of rate-making on property-related differences | (5.7 | ) |  | (6.7 | ) |  | (9.3 | ) |  | (12.0 | ) |  | (2.6 | ) |  | (2.3 | )
Amortization of excess deferred taxes | (1.1 | ) |  | (0.3 | ) |  | (0.3 | ) |  | — |  |  | (1.7 | ) |  | (0.1 | )
Adjustment for prior period taxes | (0.7 | ) |  | (2.6 | ) |  | 0.6 |  |  | (5.4 | ) |  | (0.3 | ) |  | — |
IPL’s tax benefit riders | (0.7 | ) |  | (2.2 | ) |  | (1.5 | ) |  | (4.6 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | — |  |  | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | )
Other items, net | (1.0 | ) |  | (0.7 | ) |  | (0.1 | ) |  | (1.0 | ) |  | (0.4 | ) |  | (1.2 | )
Overall income tax rate | 9.8 | % |  | 8.8 | % |  | 4.2 | % |  | (0.2 | %) |  | 17.7 | % |  | 14.2 | %
Summary Of Tax Credit Carryforwards | At September 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 |  |  | $611 |  |  |  | $522 |  |  |  | $41 |
State net operating losses | 2019-2039 |  | 677 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2039 |  | 337 |  |  | 162 |  |  | 156 |

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- Definition Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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