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Debt (Credit Facilities) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
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Commercial paper and borrowings under the single credit facility: |  |
Amount outstanding | $ 475 | $ 642
Weighted average interest rates | 5.50% | 4.60%
Available credit facility capacity | $ 525 | $ 358
IPL [Member] |  |
Commercial paper and borrowings under the single credit facility: |  |
Amount outstanding | 0 | 0
Available credit facility capacity | 150 | 100
WPL [Member] |  |
Commercial paper and borrowings under the single credit facility: |  |
Amount outstanding | $ 318 | $ 290
Weighted average interest rates | 5.40% | 4.50%
Available credit facility capacity | $ 82 | $ 110

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- Definition Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(19)(a)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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