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Related Parties (Net Intercompany Payables) (Details) - Related Party [Member] - Corporate Services [Member] - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 142	$ 135
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 71	$ 64

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