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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,350 | $ 2,261
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,000 | 934
Asset retirement obligations (AROs) [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 418 | 194
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 329 | 347
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 181 | 273
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 80 | 102
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 76 | 120
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42 | 44
IPL's Duane Arnold Energy Center purchased power agreement amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 24 | 42
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 200 | 205
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,568 | 1,577
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 885 | 831
IPL [Member] | Asset retirement obligations (AROs) [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 223 | 160
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 163 | 171
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 169 | 259
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 24 | 34
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 8 | 12
IPL [Member] | IPL's Duane Arnold Energy Center purchased power agreement amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 24 | 42
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 72 | 68
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 782 | 684
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 115 | 103
WPL [Member] | Asset retirement obligations (AROs) [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 195 | 34
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 166 | 176
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 12 | 14
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 56 | 68
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 68 | 108
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 42 | 44
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 128 | $ 137

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