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Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions | Jun. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 2,051 | $ 1,940
Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 954 | 934
Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 445 | 462
Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 140 | 128
Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 101 | 8
Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 88 | 42
Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 82 | 92
IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 78 | 90
WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 50 | 52
Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 113 | 132
IPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 1,490 | 1,443
IPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 903 | 884
IPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 220 | 228
IPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 99 | 89
IPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 69 | 4
IPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 2 | 2
IPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 61 | 66
IPL [Member] | IPL's DAEC PPA amendment [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 78 | 90
IPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 58 | 80
WPL [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 561 | 497
WPL [Member] | Tax-related [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 51 | 50
WPL [Member] | Pension and OPEB costs [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 225 | 234
WPL [Member] | Asset retirement obligations [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 41 | 39
WPL [Member] | Derivatives [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 32 | 4
WPL [Member] | Commodity cost recovery [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 86 | 40
WPL [Member] | Assets retired early [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 21 | 26
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | 50 | 52
WPL [Member] | Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory assets | $ 55 | $ 52

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