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v3.21.2

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 648 | $ 422 | $ 648 | $ 463
Average amount outstanding (based on daily outstanding balances) | $ 560 | $ 252 | $ 479 | $ 252
Weighted average interest rates | 0.20% | 0.20% | 0.20% | 1.10%
IPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 8 | $ 0 | $ 19 | $ 8
Average amount outstanding (based on daily outstanding balances) | $ 0 | 0 | $ 0 | $ 0
Weighted average interest rates | 0.20% |  | 0.20% | 0.50%
WPL [Member] |  |  |  |
Debt [Line Items] |  |  |  |
Maximum amount outstanding (based on daily outstanding balances) | $ 320 | 139 | $ 320 | $ 212
Average amount outstanding (based on daily outstanding balances) | $ 221 | $ 83 | $ 196 | $ 86
Weighted average interest rates | 0.10% | 0.20% | 0.10% | 1.20%

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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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