Related Parties (Net Intercompany Payables) (Details) - Related Party [Member] - Corporate Services [Member] - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 132	$ 129
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 70	$ 72

Amount of liabilities classified as other.

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