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Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 435 | $ 391 | $ 632 | $ 793
Average amount outstanding (based on daily outstanding balances) | $ 275 | $ 88 | $ 381 | $ 330
Weighted average interest rates | 5.50% | 5.30% | 5.50% | 4.80%
IPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 19 | $ 70 | $ 19 | $ 70
Average amount outstanding (based on daily outstanding balances) | $ 2 | $ 6 | $ 1 | $ 3
Weighted average interest rates | 5.50% | 5.30% | 5.50% | 5.30%
WPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 57 | $ 91 | $ 390 | $ 349
Average amount outstanding (based on daily outstanding balances) | $ 8 | $ 18 | $ 131 | $ 160
Weighted average interest rates | 5.40% | 5.20% | 5.50% | 4.80%

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