Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 475	$ 642
Weighted average interest rates	5.50%	4.60%
Available credit facility capacity	$ 525	$ 358
IPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	0	0
Available credit facility capacity	150	100
WPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 318	$ 290
Weighted average interest rates	5.40%	4.50%
Available credit facility capacity	$ 82	$ 110