Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 515	$ 389
Weighted average interest rates	0.20%	0.20%
Available credit facility capacity	$ 485	$ 611
IPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	0	0
Available credit facility capacity	250	250
WPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 236	$ 257
Weighted average interest rates	0.20%	0.10%
Available credit facility capacity	$ 64	$ 43