v3.25.2
Debt (Other Short-Term Borrowings) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Debt [Line Items]        
Maximum amount outstanding (based on daily outstanding balances) $ 741 $ 435 $ 741 $ 632
Average amount outstanding (based on daily outstanding balances) $ 449 $ 275 $ 495 $ 381
Weighted average interest rates 4.60% 5.50% 4.60% 5.50%
IPL [Member]        
Debt [Line Items]        
Maximum amount outstanding (based on daily outstanding balances) $ 141 $ 19 $ 141 $ 19
Average amount outstanding (based on daily outstanding balances) $ 33 $ 2 $ 43 $ 1
Weighted average interest rates 4.60% 5.50% 4.60% 5.50%
WPL [Member]        
Debt [Line Items]        
Maximum amount outstanding (based on daily outstanding balances) $ 292 $ 57 $ 292 $ 390
Average amount outstanding (based on daily outstanding balances) $ 225 $ 8 $ 193 $ 131
Weighted average interest rates 4.60% 5.40% 4.60% 5.50%