Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] gal in Thousands, T in Thousands, MWh in Thousands, Dekatherms in Thousands	9 Months Ended
	Sep. 30, 2021 Dekatherms MWh T gal
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	13,265
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	4,014
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	9,251
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	189,332
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	103,859
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	85,473
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	4,280
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	1,807
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	2,473
Diesel Fuel (Gallons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	3,654
Diesel Fuel (Gallons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	0
Diesel Fuel (Gallons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	3,654