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Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Regulatory Matters [Line Items] |  |
Regulatory assets | $ 2,269 | $ 2,046
IPL [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 1,590 | 1,386
WPL [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 679 | 660
Assets retired early [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 282 | 70
Assets retired early [Member] | IPL [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 267 | 53
Assets retired early [Member] | WPL [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 15 | $ 17
Assets retired early [Member] | Lansing Generating Station |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | 221 |
Assets retired early [Member] | Lansing Generating Station | IPL [Member] |  |
Regulatory Matters [Line Items] |  |
Regulatory assets | $ 221 |

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481878/980-340-50-1 + Details
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