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Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Dec. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Money market fund investments $ 189 $ 10
Money market fund investments weighted-average interest rate, percentage 5.00%  
IPL [Member]    
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Money market fund investments $ 180 $ 10
Money market fund investments weighted-average interest rate, percentage 5.00%  
WPL [Member]    
New Accounting Pronouncements or Change in Accounting Principle [Line Items]    
Money market fund investments $ 9  
Money market fund investments weighted-average interest rate, percentage 5.00%