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v3.20.2

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 422 | $ 472 | $ 463 | $ 601
Average amount outstanding (based on daily outstanding balances) | $ 252 | $ 400 | $ 252 | $ 476
Weighted average interest rates | 0.20% | 2.50% | 1.10% | 2.60%
IPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 0 | $ 0 | $ 8 | $ 50
Average amount outstanding (based on daily outstanding balances) | 0 | 0 | $ 0 | $ 0
Weighted average interest rates |  |  | 0.50% | 2.80%
WPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | 139 | 90 | $ 212 | $ 195
Average amount outstanding (based on daily outstanding balances) | $ 83 | $ 27 | $ 86 | $ 102
Weighted average interest rates | 0.20% | 2.30% | 1.20% | 2.50%

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