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Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | $ 56 | $ 88
Derivative assets, Net | 26 | 47
Derivative liabilities, Gross (as reported) | 94 | 98
Derivative liabilities, Net | 64 | 57
IPL [Member] |  |
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | 34 | 54
Derivative assets, Net | 17 | 32
Derivative liabilities, Gross (as reported) | 30 | 30
Derivative liabilities, Net | 13 | 8
WPL [Member] |  |
Derivative Instruments [Line Items] |  |
Derivative assets, Gross (as reported) | 22 | 34
Derivative assets, Net | 9 | 15
Derivative liabilities, Gross (as reported) | 64 | 68
Derivative liabilities, Net | $ 51 | $ 49

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