v3.25.2
Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Commodity Contracts [Member]        
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance $ 9 $ 7 $ 25 $ 24
Total net gains (losses) included in changes in net assets (realized/unrealized) 10 (5) 8 (8)
Purchases 50 59 50 59
Sales (1) (1) (1) (1)
Settlements (12) (9) (26) (23)
Ending balance 56 51 56 51
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 June 30 10 (5) 8 (8)
Commodity Contracts [Member] | IPL [Member]        
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 9 5 20 19
Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (2) 6 (6)
Purchases 40 45 40 45
Sales (1) (1) (1) (1)
Settlements (10) (7) (21) (17)
Ending balance 44 40 44 40
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 June 30 6 (2) 6 (6)
Commodity Contracts [Member] | WPL [Member]        
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 0 2 5 5
Total net gains (losses) included in changes in net assets (realized/unrealized) 4 (3) 2 (2)
Purchases 10 14 10 14
Settlements (2) (2) (5) (6)
Ending balance 12 11 12 11
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 June 30 4 (3) 2 (2)
Deferred Proceeds [Member]        
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 86 184 163 216
Total net gains (losses) included in changes in net assets (realized/unrealized) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Settlements 149 (13) 72 (45)
Ending balance 235 171 235 171
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 June 30 0 0 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 86 184 163 216
Total net gains (losses) included in changes in net assets (realized/unrealized) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Settlements 149 (13) 72 (45)
Ending balance 235 171 235 171
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 June 30 $ 0 $ 0 $ 0 $ 0