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Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2016
Income Tax [Line Items] |
Schedule of Components of Income Tax Expense (Benefit) | The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $1.8 |  |  |  | $2.0 |  |  |  | $36.6 |  |  |  | ($12.8 | ) |  |  | ($14.1 | ) |  |  | $8.9 |  |  |  | ($22.3 | ) |  |  | $4.7 |  |  |  | $2.0 |
State | 17.2 |  |  | 3.2 |  |  | 9.3 |  |  | 15.5 |  |  | 11.5 |  |  | 10.4 |  |  | 1.1 |  |  | 0.6 |  |  | 0.8 |
IPL’s tax benefit riders | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 112.8 |  |  | 120.8 |  |  | 83.5 |  |  | 59.1 |  |  | 40.7 |  |  | 10.8 |  |  | 112.3 |  |  | 76.8 |  |  | 81.1 |
State | 4.9 |  |  | 27.9 |  |  | 4.6 |  |  | (9.0 | ) |  | 3.3 |  |  | (7.9 | ) |  | 20.8 |  |  | 20.2 |  |  | 20.0 |
Production tax credits | (31.8 | ) |  | (33.1 | ) |  | (31.3 | ) |  | (14.0 | ) |  | (14.5 | ) |  | (13.8 | ) |  | (17.8 | ) |  | (18.6 | ) |  | (17.5 | )
Investment tax credits | (1.3 | ) |  | (1.4 | ) |  | (1.6 | ) |  | (0.5 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.8 | ) |  | (0.8 | ) |  | (1.0 | )
Provision recorded as a change in accrued interest | — |  |  | — |  |  | (0.1 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (0.1 | )
|  | $59.4 |  |  |  | $70.4 |  |  |  | $44.3 |  |  |  | ($5.9 | ) |  |  | ($22.7 | ) |  |  | ($48.9 | ) |  |  | $93.3 |  |  |  | $82.9 |  |  |  | $85.3 |
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
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.4 |  |  | 5.2 |  |  | 5.4 |  |  | 6.4 |  |  | 6.2 |  |  | 6.1 |  |  | 5.1 |  |  | 5.1 |  |  | 5.1 |
IPL’s tax benefit riders | (10.0 | ) |  | (10.6 | ) |  | (12.9 | ) |  | (20.1 | ) |  | (28.3 | ) |  | (39.6 | ) |  | — |  |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.5 | ) |  | (6.8 | ) |  | (7.5 | ) |  | (16.2 | ) |  | (17.2 | ) |  | (21.9 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.7 | )
Production tax credits | (7.2 | ) |  | (7.2 | ) |  | (7.1 | ) |  | (6.3 | ) |  | (8.3 | ) |  | (9.6 | ) |  | (6.2 | ) |  | (7.1 | ) |  | (6.6 | )
Adjustment of prior period taxes | (0.8 | ) |  | 0.8 |  |  | (1.3 | ) |  | (1.2 | ) |  | 0.7 |  |  | (3.0 | ) |  | (0.1 | ) |  | 0.1 |  |  | — |
Other items, net | (0.5 | ) |  | (1.1 | ) |  | (1.5 | ) |  | (0.3 | ) |  | (1.2 | ) |  | (1.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.8 | )
Overall income tax rate | 13.4 | % |  | 15.3 | % |  | 10.1 | % |  | (2.7 | %) |  | (13.1 | %) |  | (34.2 | %) |  | 32.6 | % |  | 31.8 | % |  | 32.0 | %
Schedule of Deferred Tax Assets and Liabilities | The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Deferred tax liabilities: |  |  |  |  |  |  |  |  |  |  |
Property |  | $2,919.0 |  |  |  | $2,762.9 |  |  |  | $1,677.0 |  |  |  | $1,587.8 |  |  |  | $1,124.5 |  |  |  | $1,027.0 |
Investment in ATC | 153.1 |  |  | 138.1 |  |  | — |  |  | — |  |  | — |  |  | 138.9 |
Other | 95.3 |  |  | 157.3 |  |  | 71.4 |  |  | 87.8 |  |  | 59.1 |  |  | 67.9 |
Total deferred tax liabilities | 3,167.4 |  |  | 3,058.3 |  |  | 1,748.4 |  |  | 1,675.6 |  |  | 1,183.6 |  |  | 1,233.8 |
Deferred tax assets: |  |  |  |  |  |  |  |  |  |  |
Federal credit carryforwards | 268.4 |  |  | 236.4 |  |  | 95.9 |  |  | 81.7 |  |  | 112.9 |  |  | 95.5 |
Net operating losses carryforwards - federal | 173.3 |  |  | 250.9 |  |  | 69.6 |  |  | 113.1 |  |  | 75.4 |  |  | 105.1 |
Regulatory liability - IPL’s tax benefit riders | 34.7 |  |  | 66.1 |  |  | 34.7 |  |  | 66.1 |  |  | — |  |  | — |
Net operating losses carryforwards - state | 32.9 |  |  | 38.3 |  |  | 0.6 |  |  | 1.1 |  |  | 0.1 |  |  | 3.6 |
Other | 87.9 |  |  | 85.4 |  |  | 35.8 |  |  | 35.6 |  |  | 23.6 |  |  | 24.2 |
Total deferred tax assets | 597.2 |  |  | 677.1 |  |  | 236.6 |  |  | 297.6 |  |  | 212.0 |  |  | 228.4 |
Total deferred tax liabilities, net |  | $2,570.2 |  |  |  | $2,381.2 |  |  |  | $1,511.8 |  |  |  | $1,378.0 |  |  |  | $971.6 |  |  |  | $1,005.4 |
Summary Of Tax Credit Carryforwards | At December 31, 2016, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2034 |  |  | $506 |  |  |  | $206 |  |  |  | $215 |
State net operating losses | 2018-2034 |  | 673 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2036 |  | 274 |  |  | 100 |  |  | 113 |
Schedule Of Open Tax Years | Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:
Consolidated federal income tax returns (a) | 2013 | - | 2015
Consolidated Iowa income tax returns (b) | 2013 | - | 2015
Wisconsin combined tax returns (c) | 2012 | - | 2015
(a) | The federal tax returns for 2013 and 2014 are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.
(b) | The statute of limitations for these Iowa tax returns expires three years from each filing date.
(c) | The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.
IPL [Member] |
Income Tax [Line Items] |
Schedule of Components of Income Tax Expense (Benefit) | The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $1.8 |  |  |  | $2.0 |  |  |  | $36.6 |  |  |  | ($12.8 | ) |  |  | ($14.1 | ) |  |  | $8.9 |  |  |  | ($22.3 | ) |  |  | $4.7 |  |  |  | $2.0 |
State | 17.2 |  |  | 3.2 |  |  | 9.3 |  |  | 15.5 |  |  | 11.5 |  |  | 10.4 |  |  | 1.1 |  |  | 0.6 |  |  | 0.8 |
IPL’s tax benefit riders | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 112.8 |  |  | 120.8 |  |  | 83.5 |  |  | 59.1 |  |  | 40.7 |  |  | 10.8 |  |  | 112.3 |  |  | 76.8 |  |  | 81.1 |
State | 4.9 |  |  | 27.9 |  |  | 4.6 |  |  | (9.0 | ) |  | 3.3 |  |  | (7.9 | ) |  | 20.8 |  |  | 20.2 |  |  | 20.0 |
Production tax credits | (31.8 | ) |  | (33.1 | ) |  | (31.3 | ) |  | (14.0 | ) |  | (14.5 | ) |  | (13.8 | ) |  | (17.8 | ) |  | (18.6 | ) |  | (17.5 | )
Investment tax credits | (1.3 | ) |  | (1.4 | ) |  | (1.6 | ) |  | (0.5 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.8 | ) |  | (0.8 | ) |  | (1.0 | )
Provision recorded as a change in accrued interest | — |  |  | — |  |  | (0.1 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (0.1 | )
|  | $59.4 |  |  |  | $70.4 |  |  |  | $44.3 |  |  |  | ($5.9 | ) |  |  | ($22.7 | ) |  |  | ($48.9 | ) |  |  | $93.3 |  |  |  | $82.9 |  |  |  | $85.3 |
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
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.4 |  |  | 5.2 |  |  | 5.4 |  |  | 6.4 |  |  | 6.2 |  |  | 6.1 |  |  | 5.1 |  |  | 5.1 |  |  | 5.1 |
IPL’s tax benefit riders | (10.0 | ) |  | (10.6 | ) |  | (12.9 | ) |  | (20.1 | ) |  | (28.3 | ) |  | (39.6 | ) |  | — |  |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.5 | ) |  | (6.8 | ) |  | (7.5 | ) |  | (16.2 | ) |  | (17.2 | ) |  | (21.9 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.7 | )
Production tax credits | (7.2 | ) |  | (7.2 | ) |  | (7.1 | ) |  | (6.3 | ) |  | (8.3 | ) |  | (9.6 | ) |  | (6.2 | ) |  | (7.1 | ) |  | (6.6 | )
Adjustment of prior period taxes | (0.8 | ) |  | 0.8 |  |  | (1.3 | ) |  | (1.2 | ) |  | 0.7 |  |  | (3.0 | ) |  | (0.1 | ) |  | 0.1 |  |  | — |
Other items, net | (0.5 | ) |  | (1.1 | ) |  | (1.5 | ) |  | (0.3 | ) |  | (1.2 | ) |  | (1.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.8 | )
Overall income tax rate | 13.4 | % |  | 15.3 | % |  | 10.1 | % |  | (2.7 | %) |  | (13.1 | %) |  | (34.2 | %) |  | 32.6 | % |  | 31.8 | % |  | 32.0 | %
Schedule of Deferred Tax Assets and Liabilities | The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Deferred tax liabilities: |  |  |  |  |  |  |  |  |  |  |
Property |  | $2,919.0 |  |  |  | $2,762.9 |  |  |  | $1,677.0 |  |  |  | $1,587.8 |  |  |  | $1,124.5 |  |  |  | $1,027.0 |
Investment in ATC | 153.1 |  |  | 138.1 |  |  | — |  |  | — |  |  | — |  |  | 138.9 |
Other | 95.3 |  |  | 157.3 |  |  | 71.4 |  |  | 87.8 |  |  | 59.1 |  |  | 67.9 |
Total deferred tax liabilities | 3,167.4 |  |  | 3,058.3 |  |  | 1,748.4 |  |  | 1,675.6 |  |  | 1,183.6 |  |  | 1,233.8 |
Deferred tax assets: |  |  |  |  |  |  |  |  |  |  |
Federal credit carryforwards | 268.4 |  |  | 236.4 |  |  | 95.9 |  |  | 81.7 |  |  | 112.9 |  |  | 95.5 |
Net operating losses carryforwards - federal | 173.3 |  |  | 250.9 |  |  | 69.6 |  |  | 113.1 |  |  | 75.4 |  |  | 105.1 |
Regulatory liability - IPL’s tax benefit riders | 34.7 |  |  | 66.1 |  |  | 34.7 |  |  | 66.1 |  |  | — |  |  | — |
Net operating losses carryforwards - state | 32.9 |  |  | 38.3 |  |  | 0.6 |  |  | 1.1 |  |  | 0.1 |  |  | 3.6 |
Other | 87.9 |  |  | 85.4 |  |  | 35.8 |  |  | 35.6 |  |  | 23.6 |  |  | 24.2 |
Total deferred tax assets | 597.2 |  |  | 677.1 |  |  | 236.6 |  |  | 297.6 |  |  | 212.0 |  |  | 228.4 |
Total deferred tax liabilities, net |  | $2,570.2 |  |  |  | $2,381.2 |  |  |  | $1,511.8 |  |  |  | $1,378.0 |  |  |  | $971.6 |  |  |  | $1,005.4 |
Summary Of Tax Credit Carryforwards | At December 31, 2016, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2034 |  |  | $506 |  |  |  | $206 |  |  |  | $215 |
State net operating losses | 2018-2034 |  | 673 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2036 |  | 274 |  |  | 100 |  |  | 113 |
Schedule Of Open Tax Years | Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:
Consolidated federal income tax returns (a) | 2013 | - | 2015
Consolidated Iowa income tax returns (b) | 2013 | - | 2015
Wisconsin combined tax returns (c) | 2012 | - | 2015
(a) | The federal tax returns for 2013 and 2014 are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.
(b) | The statute of limitations for these Iowa tax returns expires three years from each filing date.
(c) | The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.
WPL [Member] |
Income Tax [Line Items] |
Schedule of Components of Income Tax Expense (Benefit) | The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Current tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal |  | $1.8 |  |  |  | $2.0 |  |  |  | $36.6 |  |  |  | ($12.8 | ) |  |  | ($14.1 | ) |  |  | $8.9 |  |  |  | ($22.3 | ) |  |  | $4.7 |  |  |  | $2.0 |
State | 17.2 |  |  | 3.2 |  |  | 9.3 |  |  | 15.5 |  |  | 11.5 |  |  | 10.4 |  |  | 1.1 |  |  | 0.6 |  |  | 0.8 |
IPL’s tax benefit riders | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | (44.2 | ) |  | (49.0 | ) |  | (56.7 | ) |  | — |  |  | — |  |  | — |
Deferred tax expense (benefit): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Federal | 112.8 |  |  | 120.8 |  |  | 83.5 |  |  | 59.1 |  |  | 40.7 |  |  | 10.8 |  |  | 112.3 |  |  | 76.8 |  |  | 81.1 |
State | 4.9 |  |  | 27.9 |  |  | 4.6 |  |  | (9.0 | ) |  | 3.3 |  |  | (7.9 | ) |  | 20.8 |  |  | 20.2 |  |  | 20.0 |
Production tax credits | (31.8 | ) |  | (33.1 | ) |  | (31.3 | ) |  | (14.0 | ) |  | (14.5 | ) |  | (13.8 | ) |  | (17.8 | ) |  | (18.6 | ) |  | (17.5 | )
Investment tax credits | (1.3 | ) |  | (1.4 | ) |  | (1.6 | ) |  | (0.5 | ) |  | (0.6 | ) |  | (0.6 | ) |  | (0.8 | ) |  | (0.8 | ) |  | (1.0 | )
Provision recorded as a change in accrued interest | — |  |  | — |  |  | (0.1 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (0.1 | )
|  | $59.4 |  |  |  | $70.4 |  |  |  | $44.3 |  |  |  | ($5.9 | ) |  |  | ($22.7 | ) |  |  | ($48.9 | ) |  |  | $93.3 |  |  |  | $82.9 |  |  |  | $85.3 |
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
| 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014 |  | 2016 |  | 2015 |  | 2014
Statutory federal income tax rate | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | % |  | 35.0 | %
State income taxes, net of federal benefits | 5.4 |  |  | 5.2 |  |  | 5.4 |  |  | 6.4 |  |  | 6.2 |  |  | 6.1 |  |  | 5.1 |  |  | 5.1 |  |  | 5.1 |
IPL’s tax benefit riders | (10.0 | ) |  | (10.6 | ) |  | (12.9 | ) |  | (20.1 | ) |  | (28.3 | ) |  | (39.6 | ) |  | — |  |  | — |  |  | — |
Effect of rate-making on property-related differences | (8.5 | ) |  | (6.8 | ) |  | (7.5 | ) |  | (16.2 | ) |  | (17.2 | ) |  | (21.9 | ) |  | (0.7 | ) |  | (0.5 | ) |  | (0.7 | )
Production tax credits | (7.2 | ) |  | (7.2 | ) |  | (7.1 | ) |  | (6.3 | ) |  | (8.3 | ) |  | (9.6 | ) |  | (6.2 | ) |  | (7.1 | ) |  | (6.6 | )
Adjustment of prior period taxes | (0.8 | ) |  | 0.8 |  |  | (1.3 | ) |  | (1.2 | ) |  | 0.7 |  |  | (3.0 | ) |  | (0.1 | ) |  | 0.1 |  |  | — |
Other items, net | (0.5 | ) |  | (1.1 | ) |  | (1.5 | ) |  | (0.3 | ) |  | (1.2 | ) |  | (1.2 | ) |  | (0.5 | ) |  | (0.8 | ) |  | (0.8 | )
Overall income tax rate | 13.4 | % |  | 15.3 | % |  | 10.1 | % |  | (2.7 | %) |  | (13.1 | %) |  | (34.2 | %) |  | 32.6 | % |  | 31.8 | % |  | 32.0 | %
Schedule of Deferred Tax Assets and Liabilities | The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Deferred tax liabilities: |  |  |  |  |  |  |  |  |  |  |
Property |  | $2,919.0 |  |  |  | $2,762.9 |  |  |  | $1,677.0 |  |  |  | $1,587.8 |  |  |  | $1,124.5 |  |  |  | $1,027.0 |
Investment in ATC | 153.1 |  |  | 138.1 |  |  | — |  |  | — |  |  | — |  |  | 138.9 |
Other | 95.3 |  |  | 157.3 |  |  | 71.4 |  |  | 87.8 |  |  | 59.1 |  |  | 67.9 |
Total deferred tax liabilities | 3,167.4 |  |  | 3,058.3 |  |  | 1,748.4 |  |  | 1,675.6 |  |  | 1,183.6 |  |  | 1,233.8 |
Deferred tax assets: |  |  |  |  |  |  |  |  |  |  |
Federal credit carryforwards | 268.4 |  |  | 236.4 |  |  | 95.9 |  |  | 81.7 |  |  | 112.9 |  |  | 95.5 |
Net operating losses carryforwards - federal | 173.3 |  |  | 250.9 |  |  | 69.6 |  |  | 113.1 |  |  | 75.4 |  |  | 105.1 |
Regulatory liability - IPL’s tax benefit riders | 34.7 |  |  | 66.1 |  |  | 34.7 |  |  | 66.1 |  |  | — |  |  | — |
Net operating losses carryforwards - state | 32.9 |  |  | 38.3 |  |  | 0.6 |  |  | 1.1 |  |  | 0.1 |  |  | 3.6 |
Other | 87.9 |  |  | 85.4 |  |  | 35.8 |  |  | 35.6 |  |  | 23.6 |  |  | 24.2 |
Total deferred tax assets | 597.2 |  |  | 677.1 |  |  | 236.6 |  |  | 297.6 |  |  | 212.0 |  |  | 228.4 |
Total deferred tax liabilities, net |  | $2,570.2 |  |  |  | $2,381.2 |  |  |  | $1,511.8 |  |  |  | $1,378.0 |  |  |  | $971.6 |  |  |  | $1,005.4 |
Summary Of Tax Credit Carryforwards | At December 31, 2016, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2030-2034 |  |  | $506 |  |  |  | $206 |  |  |  | $215 |
State net operating losses | 2018-2034 |  | 673 |  |  | 12 |  |  | 2 |
Federal tax credits | 2022-2036 |  | 274 |  |  | 100 |  |  | 113 |
Schedule Of Open Tax Years | Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:
Consolidated federal income tax returns (a) | 2013 | - | 2015
Consolidated Iowa income tax returns (b) | 2013 | - | 2015
Wisconsin combined tax returns (c) | 2012 | - | 2015
(a) | The federal tax returns for 2013 and 2014 are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.
(b) | The statute of limitations for these Iowa tax returns expires three years from each filing date.
(c) | The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

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