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Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | --- | --- | ---
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | $ 7 | $ 24 | $ (5) | $ 19
Excluding Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets |  | 3 |  |
Fair value, net derivative liabilities | (1) |  |  |
Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | 8 | 21 |  |
IPL [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | 5 | 19 | 0 | 16
IPL [Member] | Excluding Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets |  | 3 |  |
Fair value, net derivative liabilities | (1) |  |  |
IPL [Member] | Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | 6 | 16 |  |
WPL [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | 2 | 5 | $ (5) | $ 3
WPL [Member] | Excluding Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative liabilities | 0 | 0 |  |
WPL [Member] | Financial Transmission Rights [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, net derivative assets | $ 2 | $ 5 |  |

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- Definition Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -SubTopic 10 -Topic 820 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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