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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,274.0 | $ 2,261.0
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 989.0 | 934.0
AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 401.0 | 194.0
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 315.0 | 347.0
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 180.0 | 273.0
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 68.0 | 120.0
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 60.0 | 102.0
Non-service pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 51.0 | 46.0
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42.0 | 44.0
IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 18.0 | 42.0
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 150.0 | 159.0
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,586.0 | 1,577.0
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 870.0 | 831.0
IPL [Member] | AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 281.0 | 160.0
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 157.0 | 171.0
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 168.0 | 259.0
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 2.0 | 12.0
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 15.0 | 34.0
IPL [Member] | Non-service pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 19.0 | 18.0
IPL [Member] | IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 18.0 | 42.0
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 56.0 | 50.0
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 688.0 | 684.0
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 119.0 | 103.0
WPL [Member] | AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 120.0 | 34.0
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 158.0 | 176.0
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 12.0 | 14.0
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 66.0 | 108.0
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 45.0 | 68.0
WPL [Member] | Non-service pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 32.0 | 28.0
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42.0 | 44.0
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 94.0 | $ 109.0

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