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Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | $ 129 | $ 237
Derivative assets, Net | 108 | 193
Derivative liabilities, Gross (as reported) | 66 | 79
Derivative liabilities, Net | 45 | 35
IPL [Member] |  |
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | 85 | 138
Derivative assets, Net | 73 | 108
Derivative liabilities, Gross (as reported) | 21 | 46
Derivative liabilities, Net | 9 | 16
WPL [Member] |  |
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | 44 | 99
Derivative assets, Net | 35 | 85
Derivative liabilities, Gross (as reported) | 45 | 33
Derivative liabilities, Net | $ 36 | $ 19

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