Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 678	$ 632
Average amount outstanding (based on daily outstanding balances)	$ 541	$ 487
Weighted average interest rates	4.50%	5.50%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 127	$ 14
Average amount outstanding (based on daily outstanding balances)	$ 53	$ 1
Weighted average interest rates	4.60%	5.50%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 224	$ 390
Average amount outstanding (based on daily outstanding balances)	$ 159	$ 255
Weighted average interest rates	4.50%	5.50%