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Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Administrative and General Services Billings [Member] | IPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | $ 181 | $ 181 | $ 180
Administrative and General Services Billings [Member] | WPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | 163 | 155 | 154
Transmission Sales Credited [Member] | IPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | 11 | 19 | 22
Transmission Sales Credited [Member] | WPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | 55 | 74 | 23
Transmission Purchases Billed [Member] | IPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | 431 | 435 | 441
Transmission Purchases Billed [Member] | WPL [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Amounts billed between related parties | $ 35 | $ 174 | $ 116

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