Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 88	$ 558
Weighted average interest rates	3.80%	4.50%
Available credit facility capacity	$ 1,212	$ 742
IPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 88	$ 50
Weighted average interest rates	3.80%	4.60%
Available credit facility capacity	$ 262	$ 250
WPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	0	$ 183
Weighted average interest rates		4.50%
Available credit facility capacity	$ 400	$ 217