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Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Corporate Services Billings [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | $ 42 | $ 46 | $ 134 | $ 134
Corporate Services Billings [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 38 | 40 | 124 | 120
Sales Credited [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 0 | 3 | 0 | 11
Sales Credited [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 29 | 23 | 66 | 45
Purchases Billed [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 130 | 133 | 332 | 320
Purchases Billed [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | $ 18 | $ 5 | $ 41 | $ 21

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