Debt (Credit Facilities) (Details) $ in Millions	Mar. 31, 2023 USD ($)
Debt [Line Items]
Amount outstanding	$ 60
Weighted average interest rates	5.10%
Available credit facility capacity	$ 940
IPL [Member]
Debt [Line Items]
Amount outstanding	0
Available credit facility capacity	250
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 60
Weighted average interest rates	5.10%
Available credit facility capacity	$ 240