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Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax [Line Items] |  |  |  |
Statutory federal income tax rate |  | 21.00% | 21.00% | 35.00%
Income tax expense (benefits) Federal Tax Reform |  |  | $ (5.6) | $ (18.1)
Overall income tax rate |  | 10.80% | 8.40% | 12.50%
IPL [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Statutory federal income tax rate |  | 21.00% | 21.00% | 35.00%
Income tax expense (benefits) Federal Tax Reform |  |  | $ (1.1) | $ 3.8
Overall income tax rate |  | 7.60% | (1.20%) | (5.00%)
WPL [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Statutory federal income tax rate |  | 21.00% | 21.00% | 35.00%
Income tax expense (benefits) Federal Tax Reform |  |  | $ (5.5) | $ (14.5)
Overall income tax rate |  | 17.50% | 14.80% | 24.90%
State [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate |  | 12.00% |  |
State [Member] | Forecast [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate | 9.80% |  |  |
State [Member] | IPL [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate |  | 12.00% |  |
State [Member] | IPL [Member] | Forecast [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate | 9.80% |  |  |
State [Member] | WPL [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate |  | 12.00% |  |
State [Member] | WPL [Member] | Forecast [Member] |  |  |  |
Income Tax [Line Items] |  |  |  |
Overall income tax rate | 9.80% |  |  |

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