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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,261 | $ 2,046
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 934 | 929
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 347 | 392
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 273 | 70
AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 194 | 151
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 120 | 160
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 102 | 84
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 44 | 48
IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42 | 66
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 205 | 146
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,577 | 1,386
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 831 | 848
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 171 | 197
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 259 | 53
IPL [Member] | AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 160 | 110
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 12 | 1
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 34 | 48
IPL [Member] | IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42 | 66
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 68 | 63
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 684 | 660
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 103 | 81
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 176 | 195
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 14 | 17
WPL [Member] | AROs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 34 | 41
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 108 | 159
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 68 | 36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 44 | 48
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 137 | $ 83

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