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v3.21.2

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 571 | $ 271 | $ 578 | $ 463
Average amount outstanding (based on daily outstanding balances) | $ 452 | $ 121 | $ 438 | $ 252
Weighted average interest rates | 0.20% | 0.50% | 0.20% | 1.50%
IPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 19 | $ 8 | $ 19 | $ 8
Average amount outstanding (based on daily outstanding balances) | $ 1 | $ 0 | $ 0 | $ 0
Weighted average interest rates | 0.20% | 0.50% | 0.20% | 0.50%
WPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 232 | $ 182 | $ 275 | $ 212
Average amount outstanding (based on daily outstanding balances) | $ 177 | $ 9 | $ 183 | $ 88
Weighted average interest rates | 0.10% | 0.50% | 0.10% | 1.70%

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- Definition For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph (a) Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph (b) -Subparagraph (1) + Details
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