Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - Related Party [Member] - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 110	$ 103
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 65	$ 56