Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 793	$ 665
Average amount outstanding (based on daily outstanding balances)	$ 386	$ 411
Weighted average interest rates	5.20%	2.10%
IPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 70	$ 0
Average amount outstanding (based on daily outstanding balances)	$ 2	$ 0
Weighted average interest rates	5.30%	0.00%
WPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 349	$ 325
Average amount outstanding (based on daily outstanding balances)	$ 157	$ 153
Weighted average interest rates	5.10%	1.60%