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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Sep. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,041 | $ 1,940
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 913 | 934
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 436 | 462
Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 145 | 128
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 129 | 42
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 102 | 8
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 75 | 92
IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 72 | 90
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 49 | 52
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 120 | 132
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,423 | 1,443
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 842 | 884
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 216 | 228
IPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 104 | 89
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 2 | 2
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 67 | 4
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 56 | 66
IPL [Member] | IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 72 | 90
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 64 | 80
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 618 | 497
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 71 | 50
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 220 | 234
WPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 41 | 39
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 127 | 40
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 35 | 4
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 19 | 26
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 49 | 52
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 56 | $ 52

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