Debt (Credit Facilities) (Details) $ in Millions	Jun. 30, 2024 USD ($)
Debt [Line Items]
Amount outstanding	$ 52
Weighted average interest rates	5.50%
Available credit facility capacity	$ 948
IPL [Member]
Debt [Line Items]
Amount outstanding	$ 0
Weighted average interest rates	0.00%
Available credit facility capacity	$ 250
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 0
Weighted average interest rates	0.00%
Available credit facility capacity	$ 300