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Income Taxes | 3 Months Ended
--- | ---
Mar. 31, 2018
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES 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 March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Statutory federal income tax rate | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 5.4 |  |  | 8.5 |  |  | 6.3 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (7.4 | ) |  | (7.5 | ) |  | (13.5 | ) |  | (17.9 | ) |  | (2.4 | ) |  | (1.7 | )
Production tax credits | (5.5 | ) |  | (5.9 | ) |  | (5.4 | ) |  | (6.6 | ) |  | (6.7 | ) |  | (7.0 | )
IPL’s tax benefit riders | (2.2 | ) |  | (7.8 | ) |  | (4.7 | ) |  | (19.4 | ) |  | — |  |  | — |
Other items, net | (1.4 | ) |  | (4.4 | ) |  | — |  |  | (7.6 | ) |  | (0.3 | ) |  | (0.4 | )
Overall income tax rate | 12.0 | % |  | 14.8 | % |  | 5.9 | % |  | (10.2 | %) |  | 17.8 | % |  | 31.0 | %
Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018. Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2037 |  |  | $774 |  |  |  | $497 |  |  |  | $176 |
State net operating losses | 2018-2038 |  | 707 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 277 |  |  | 123 |  |  | 136 |
IPL [Member] |
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES 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 March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Statutory federal income tax rate | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 5.4 |  |  | 8.5 |  |  | 6.3 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (7.4 | ) |  | (7.5 | ) |  | (13.5 | ) |  | (17.9 | ) |  | (2.4 | ) |  | (1.7 | )
Production tax credits | (5.5 | ) |  | (5.9 | ) |  | (5.4 | ) |  | (6.6 | ) |  | (6.7 | ) |  | (7.0 | )
IPL’s tax benefit riders | (2.2 | ) |  | (7.8 | ) |  | (4.7 | ) |  | (19.4 | ) |  | — |  |  | — |
Other items, net | (1.4 | ) |  | (4.4 | ) |  | — |  |  | (7.6 | ) |  | (0.3 | ) |  | (0.4 | )
Overall income tax rate | 12.0 | % |  | 14.8 | % |  | 5.9 | % |  | (10.2 | %) |  | 17.8 | % |  | 31.0 | %
Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018. Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2037 |  |  | $774 |  |  |  | $497 |  |  |  | $176 |
State net operating losses | 2018-2038 |  | 707 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 277 |  |  | 123 |  |  | 136 |
WPL [Member] |
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES 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 March 31 | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Statutory federal income tax rate | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | % |  | 21.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 7.5 |  |  | 5.4 |  |  | 8.5 |  |  | 6.3 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (7.4 | ) |  | (7.5 | ) |  | (13.5 | ) |  | (17.9 | ) |  | (2.4 | ) |  | (1.7 | )
Production tax credits | (5.5 | ) |  | (5.9 | ) |  | (5.4 | ) |  | (6.6 | ) |  | (6.7 | ) |  | (7.0 | )
IPL’s tax benefit riders | (2.2 | ) |  | (7.8 | ) |  | (4.7 | ) |  | (19.4 | ) |  | — |  |  | — |
Other items, net | (1.4 | ) |  | (4.4 | ) |  | — |  |  | (7.6 | ) |  | (0.3 | ) |  | (0.4 | )
Overall income tax rate | 12.0 | % |  | 14.8 | % |  | 5.9 | % |  | (10.2 | %) |  | 17.8 | % |  | 31.0 | %
Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018. Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2037 |  |  | $774 |  |  |  | $497 |  |  |  | $176 |
State net operating losses | 2018-2038 |  | 707 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 277 |  |  | 123 |  |  | 136 |

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- Definition Income tax + References No definition available. + Details
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- Definition The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -URI http://asc.fasb.org/topic&trid=2144680 + Details
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