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Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2024 | Mar. 31, 2023
Commodity Contracts [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance | $ 24 | $ 19
Total net gains (losses) included in changes in net assets (realized/unrealized) | (3) | (4)
Settlements | (14) | (20)
Ending balance | 7 | (5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | (3) | (4)
Commodity Contracts [Member] | IPL [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance | 19 | 16
Total net gains (losses) included in changes in net assets (realized/unrealized) | (4) | 1
Settlements | (10) | (17)
Ending balance | 5 | 0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | (4) | 1
Commodity Contracts [Member] | WPL [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance | 5 | 3
Total net gains (losses) included in changes in net assets (realized/unrealized) | 1 | (5)
Settlements | (4) | (3)
Ending balance | 2 | (5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | 1 | (5)
Deferred Proceeds [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance | 216 | 185
Total net gains (losses) included in changes in net assets (realized/unrealized) | 0 | 0
Settlements | (32) | (32)
Ending balance | 184 | 153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | 0 | 0
Deferred Proceeds [Member] | IPL [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance | 216 | 185
Total net gains (losses) included in changes in net assets (realized/unrealized) | 0 | 0
Settlements | (32) | (32)
Ending balance | 184 | 153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | $ 0 | $ 0

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- Definition Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition Amount of settlement 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 -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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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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