Debt (Credit Facilities) (Details) $ in Millions	Jun. 30, 2023 USD ($)
Debt [Line Items]
Amount outstanding	$ 391
Weighted average interest rates	5.30%
Available credit facility capacity	$ 554
IPL [Member]
Debt [Line Items]
Amount outstanding	$ 0
Weighted average interest rates	0.00%
Available credit facility capacity	$ 195
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 44
Weighted average interest rates	5.20%
Available credit facility capacity	$ 256