Fair Value Measurements (Schedule Of Face And Fair Value Of Debt) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Face Value	$ 1,815,300,000	$ 1,829,300,000
Fair Value	2,062,300,000	2,008,900,000
Indianapolis Power And Light Company [Member]
Debt Instrument [Line Items]
Face Value	1,015,300,000	1,029,300,000
Fair Value	1,194,300,000	1,181,900,000
Fixed Rate [Member]
Debt Instrument [Line Items]
Face Value	1,765,300,000	1,765,300,000
Fair Value	2,012,300,000	1,944,900,000
Fixed Rate [Member] | Indianapolis Power And Light Company [Member]
Debt Instrument [Line Items]
Face Value	965,300,000	965,300,000
Fair Value	1,144,300,000	1,117,900,000
Variable Rate [Member]
Debt Instrument [Line Items]
Face Value	50,000,000	64,000,000
Fair Value	50,000,000	64,000,000
Variable Rate [Member] | Indianapolis Power And Light Company [Member]
Debt Instrument [Line Items]
Face Value	50,000,000	64,000,000
Fair Value	$ 50,000,000	$ 64,000,000