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Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Commodity Contracts Derivative Assets and (Liabilities), net [Member]    
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance, January 1 $ 19 $ 29
Total net gains (losses) included in changes in net assets (realized/unrealized) 3 (18)
Purchases 62 79
Sales (3) (2)
Settlements (57) (69)
Ending balance, December 31 24 19
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 3 (18)
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | IPL [Member]    
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance, January 1 16 18
Total net gains (losses) included in changes in net assets (realized/unrealized) (3) (12)
Purchases 51 58
Sales (3) (1)
Settlements (42) (47)
Ending balance, December 31 19 16
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 (3) (13)
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | WPL [Member]    
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance, January 1 3 11
Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (6)
Purchases 11 21
Sales 0 (1)
Settlements (15) (22)
Ending balance, December 31 5 3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 6 (5)
Deferred Proceeds [Member]    
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance, January 1 185 214
Total net gains (losses) included in changes in net assets (realized/unrealized) 0 0
Purchases 0 0
Sales 0 0
Settlements 31 (29)
Ending balance, December 31 216 185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 0 0
Deferred Proceeds [Member] | IPL [Member]    
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance, January 1 185 214
Total net gains (losses) included in changes in net assets (realized/unrealized) 0 0
Purchases 0 0
Sales 0 0
Settlements 31 (29)
Ending balance, December 31 216 185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 $ 0 $ 0