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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,080 | $ 2,046
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 942 | 929
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 385 | 392
Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 156 | 151
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 152 | 160
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 101 | 84
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 67 | 70
IPL's Duane Arnold Energy Center PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 60 | 66
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 48 | 48
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 169 | 146
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,383 | 1,386
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 857 | 848
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 193 | 197
IPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 115 | 110
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 4 | 1
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 37 | 48
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 51 | 53
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 60 | 66
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 66 | 63
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 697 | 660
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 85 | 81
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 192 | 195
WPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 41 | 41
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 148 | 159
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 64 | 36
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 16 | 17
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 48 | 48
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 103 | $ 83

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