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Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2024 | Mar. 31, 2023
Corporate Services Billings [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | $ 43 | $ 40
Corporate Services Billings [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 40 | 36
Sales Credited [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 0 | 7
Sales Credited [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 22 | 13
Purchases Billed [Member] | IPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | 96 | 93
Purchases Billed [Member] | WPL [Member] |  |
Related Party Transactions [Line Items] |  |
Amounts billed between related parties | $ 7 | $ 15

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