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Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Commodity Contracts Derivative Assets and (Liabilities), net [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance, January 1 | $ 19 | $ 29
Total net gains (losses) included in changes in net assets (realized/unrealized) | 3 | (18)
Purchases | 62 | 79
Sales | (3) | (2)
Settlements | (57) | (69)
Ending balance, December 31 | 24 | 19
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 December 31 | 3 | (18)
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | IPL [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance, January 1 | 16 | 18
Total net gains (losses) included in changes in net assets (realized/unrealized) | (3) | (12)
Purchases | 51 | 58
Sales | (3) | (1)
Settlements | (42) | (47)
Ending balance, December 31 | 19 | 16
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 December 31 | (3) | (13)
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | WPL [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance, January 1 | 3 | 11
Total net gains (losses) included in changes in net assets (realized/unrealized) | 6 | (6)
Purchases | 11 | 21
Sales | 0 | (1)
Settlements | (15) | (22)
Ending balance, December 31 | 5 | 3
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 December 31 | 6 | (5)
Deferred Proceeds [Member] |  |
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning balance, January 1 | 185 | 214
Total net gains (losses) included in changes in net assets (realized/unrealized) | 0 | 0
Purchases | 0 | 0
Sales | 0 | 0
Settlements | 31 | (29)
Ending balance, December 31 | 216 | 185
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 December 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, January 1 | 185 | 214
Total net gains (losses) included in changes in net assets (realized/unrealized) | 0 | 0
Purchases | 0 | 0
Sales | 0 | 0
Settlements | 31 | (29)
Ending balance, December 31 | 216 | 185
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 December 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 purchases 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 Amount of sale 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 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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