Utility Plant In Service (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Public Utility, Property, Plant and Equipment [Line Items]
Direct first mortgage lien	$ 965.3
Indianapolis Power And Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Direct first mortgage lien	965.3
Non-Legal [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Removal costs of utility plant in service	575.9	552.0
Non-Legal [Member] | Indianapolis Power And Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Removal costs of utility plant in service	575.9	552.0
Legal [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Removal costs of utility plant in service	17.6	16.6
Legal [Member] | Indianapolis Power And Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Removal costs of utility plant in service	$ 17.6	$ 16.6