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Income Taxes | 9 Months Ended
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Sep. 30, 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 September 30 | 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 | 6.9 |  |  | 5.7 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.2 |
Effect of rate-making on property-related differences | (6.3 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (22.6 | ) |  | (2.1 | ) |  | (1.9 | )
Production tax credits | (5.4 | ) |  | (6.2 | ) |  | (5.5 | ) |  | (7.0 | ) |  | (6.4 | ) |  | (7.0 | )
Adjustment for prior period taxes | (5.7 | ) |  | (2.0 | ) |  | (10.2 | ) |  | (3.5 | ) |  | — |  |  | 0.8 |
IPL’s tax benefit riders | (2.3 | ) |  | (8.3 | ) |  | (4.8 | ) |  | (20.9 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | ) |  | — |
Other items, net | (0.4 | ) |  | (0.9 | ) |  | (0.6 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.5 | )
Overall income tax rate | 5.3 | % |  | 13.2 | % |  | (4.8 | %) |  | (13.2 | %) |  | 11.8 | % |  | 31.6 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | 6.9 |  |  | 5.6 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (6.7 | ) |  | (9.1 | ) |  | (12.0 | ) |  | (20.6 | ) |  | (2.3 | ) |  | (1.8 | )
Production tax credits | (5.4 | ) |  | (6.0 | ) |  | (5.4 | ) |  | (6.8 | ) |  | (6.6 | ) |  | (7.0 | )
Adjustment for prior period taxes | (2.6 | ) |  | (1.3 | ) |  | (5.4 | ) |  | (3.3 | ) |  | — |  |  | 0.3 |
IPL’s tax benefit riders | (2.2 | ) |  | (8.1 | ) |  | (4.6 | ) |  | (20.1 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | ) |  | — |
Other items, net | (1.0 | ) |  | (1.2 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.3 | ) |  | (0.5 | )
Overall income tax rate | 8.8 | % |  | 14.9 | % |  | (0.2 | %) |  | (9.8 | %) |  | 14.2 | % |  | 31.1 | %
Federal Tax Reform Adjustments - In December 2017, Federal Tax Reform was enacted, which had a material impact on Alliant Energy’s, IPL’s and WPL’s financial statements in the fourth quarter of 2017 since changes in tax laws must be recognized in the period in which the law was enacted. During the third quarter of 2018, additional rules were issued, including clarifications of the treatment of bonus depreciation deductions, which impacted the federal income tax return for the calendar year 2017. As result of these clarifying rules, Alliant Energy, IPL and WPL recorded tax benefits of $5.6 million, $1.1 million and $5.5 million, respectively, in the third quarter of 2018. Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $96.8 million, $22.3 million and $57.2 million, respectively. The increases were primarily due to property-related differences, which were partially offset by increases in federal credit carryforwards. Alliant Energy’s and IPL’s increases were also partially offset by the effects of Iowa tax reform, which is discussed in Note 2. WPL’s increase was also partially due to the utilization of federal net operating losses. Carryforwards - At September 30, 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 |  |  | $804 |  |  |  | $563 |  |  |  | $144 |
State net operating losses | 2018-2038 |  | 765 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 290 |  |  | 129 |  |  | 143 |
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 September 30 | 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 | 6.9 |  |  | 5.7 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.2 |
Effect of rate-making on property-related differences | (6.3 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (22.6 | ) |  | (2.1 | ) |  | (1.9 | )
Production tax credits | (5.4 | ) |  | (6.2 | ) |  | (5.5 | ) |  | (7.0 | ) |  | (6.4 | ) |  | (7.0 | )
Adjustment for prior period taxes | (5.7 | ) |  | (2.0 | ) |  | (10.2 | ) |  | (3.5 | ) |  | — |  |  | 0.8 |
IPL’s tax benefit riders | (2.3 | ) |  | (8.3 | ) |  | (4.8 | ) |  | (20.9 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | ) |  | — |
Other items, net | (0.4 | ) |  | (0.9 | ) |  | (0.6 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.5 | )
Overall income tax rate | 5.3 | % |  | 13.2 | % |  | (4.8 | %) |  | (13.2 | %) |  | 11.8 | % |  | 31.6 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | 6.9 |  |  | 5.6 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (6.7 | ) |  | (9.1 | ) |  | (12.0 | ) |  | (20.6 | ) |  | (2.3 | ) |  | (1.8 | )
Production tax credits | (5.4 | ) |  | (6.0 | ) |  | (5.4 | ) |  | (6.8 | ) |  | (6.6 | ) |  | (7.0 | )
Adjustment for prior period taxes | (2.6 | ) |  | (1.3 | ) |  | (5.4 | ) |  | (3.3 | ) |  | — |  |  | 0.3 |
IPL’s tax benefit riders | (2.2 | ) |  | (8.1 | ) |  | (4.6 | ) |  | (20.1 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | ) |  | — |
Other items, net | (1.0 | ) |  | (1.2 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.3 | ) |  | (0.5 | )
Overall income tax rate | 8.8 | % |  | 14.9 | % |  | (0.2 | %) |  | (9.8 | %) |  | 14.2 | % |  | 31.1 | %
Federal Tax Reform Adjustments - In December 2017, Federal Tax Reform was enacted, which had a material impact on Alliant Energy’s, IPL’s and WPL’s financial statements in the fourth quarter of 2017 since changes in tax laws must be recognized in the period in which the law was enacted. During the third quarter of 2018, additional rules were issued, including clarifications of the treatment of bonus depreciation deductions, which impacted the federal income tax return for the calendar year 2017. As result of these clarifying rules, Alliant Energy, IPL and WPL recorded tax benefits of $5.6 million, $1.1 million and $5.5 million, respectively, in the third quarter of 2018. Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $96.8 million, $22.3 million and $57.2 million, respectively. The increases were primarily due to property-related differences, which were partially offset by increases in federal credit carryforwards. Alliant Energy’s and IPL’s increases were also partially offset by the effects of Iowa tax reform, which is discussed in Note 2. WPL’s increase was also partially due to the utilization of federal net operating losses. Carryforwards - At September 30, 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 |  |  | $804 |  |  |  | $563 |  |  |  | $144 |
State net operating losses | 2018-2038 |  | 765 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 290 |  |  | 129 |  |  | 143 |
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 September 30 | 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 | 6.9 |  |  | 5.7 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.2 |
Effect of rate-making on property-related differences | (6.3 | ) |  | (10.1 | ) |  | (11.5 | ) |  | (22.6 | ) |  | (2.1 | ) |  | (1.9 | )
Production tax credits | (5.4 | ) |  | (6.2 | ) |  | (5.5 | ) |  | (7.0 | ) |  | (6.4 | ) |  | (7.0 | )
Adjustment for prior period taxes | (5.7 | ) |  | (2.0 | ) |  | (10.2 | ) |  | (3.5 | ) |  | — |  |  | 0.8 |
IPL’s tax benefit riders | (2.3 | ) |  | (8.3 | ) |  | (4.8 | ) |  | (20.9 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (2.5 | ) |  | — |  |  | (0.9 | ) |  | — |  |  | (6.4 | ) |  | — |
Other items, net | (0.4 | ) |  | (0.9 | ) |  | (0.6 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.5 | )
Overall income tax rate | 5.3 | % |  | 13.2 | % |  | (4.8 | %) |  | (13.2 | %) |  | 11.8 | % |  | 31.6 | %
| Alliant Energy |  | IPL |  | WPL
Nine Months Ended September 30 | 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 | 6.9 |  |  | 5.6 |  |  | 7.7 |  |  | 6.5 |  |  | 6.2 |  |  | 5.1 |
Effect of rate-making on property-related differences | (6.7 | ) |  | (9.1 | ) |  | (12.0 | ) |  | (20.6 | ) |  | (2.3 | ) |  | (1.8 | )
Production tax credits | (5.4 | ) |  | (6.0 | ) |  | (5.4 | ) |  | (6.8 | ) |  | (6.6 | ) |  | (7.0 | )
Adjustment for prior period taxes | (2.6 | ) |  | (1.3 | ) |  | (5.4 | ) |  | (3.3 | ) |  | — |  |  | 0.3 |
IPL’s tax benefit riders | (2.2 | ) |  | (8.1 | ) |  | (4.6 | ) |  | (20.1 | ) |  | — |  |  | — |
Federal Tax Reform adjustments | (1.2 | ) |  | — |  |  | (0.5 | ) |  | — |  |  | (2.8 | ) |  | — |
Other items, net | (1.0 | ) |  | (1.2 | ) |  | (1.0 | ) |  | (0.5 | ) |  | (1.3 | ) |  | (0.5 | )
Overall income tax rate | 8.8 | % |  | 14.9 | % |  | (0.2 | %) |  | (9.8 | %) |  | 14.2 | % |  | 31.1 | %
Federal Tax Reform Adjustments - In December 2017, Federal Tax Reform was enacted, which had a material impact on Alliant Energy’s, IPL’s and WPL’s financial statements in the fourth quarter of 2017 since changes in tax laws must be recognized in the period in which the law was enacted. During the third quarter of 2018, additional rules were issued, including clarifications of the treatment of bonus depreciation deductions, which impacted the federal income tax return for the calendar year 2017. As result of these clarifying rules, Alliant Energy, IPL and WPL recorded tax benefits of $5.6 million, $1.1 million and $5.5 million, respectively, in the third quarter of 2018. Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $96.8 million, $22.3 million and $57.2 million, respectively. The increases were primarily due to property-related differences, which were partially offset by increases in federal credit carryforwards. Alliant Energy’s and IPL’s increases were also partially offset by the effects of Iowa tax reform, which is discussed in Note 2. WPL’s increase was also partially due to the utilization of federal net operating losses. Carryforwards - At September 30, 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 |  |  | $804 |  |  |  | $563 |  |  |  | $144 |
State net operating losses | 2018-2038 |  | 765 |  |  | 13 |  |  | 2 |
Federal tax credits | 2022-2038 |  | 290 |  |  | 129 |  |  | 143 |

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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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