Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 632	$ 793
Average amount outstanding (based on daily outstanding balances)	$ 327	$ 386
Weighted average interest rates	5.30%	5.20%
IPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 80	$ 70
Average amount outstanding (based on daily outstanding balances)	$ 1	$ 2
Weighted average interest rates	5.10%	5.30%
WPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 390	$ 349
Average amount outstanding (based on daily outstanding balances)	$ 70	$ 157
Weighted average interest rates	5.40%	5.10%