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Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 793 | $ 665
Average amount outstanding (based on daily outstanding balances) | $ 386 | $ 411
Weighted average interest rates | 5.20% | 2.10%
IPL [Member] |  |
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 70 | $ 0
Average amount outstanding (based on daily outstanding balances) | $ 2 | $ 0
Weighted average interest rates | 5.30% | 0.00%
WPL [Member] |  |
Debt Instrument [Line Items] |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 349 | $ 325
Average amount outstanding (based on daily outstanding balances) | $ 157 | $ 153
Weighted average interest rates | 5.10% | 1.60%

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