Fair Value Measurements (Summary Of Fair Value Assets And Liabilities Measured On A Recurring Basis, Level 3) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financial transmission rights	$ 2,419	$ 2,779
Total financial assets measured at fair value	2,419	2,779
Other derivative liabilities	170	181
Total financial liabilities measured at fair value	170	181
Indianapolis Power And Light Company [Member]
Financial transmission rights	2,419	2,779
Total financial assets measured at fair value	2,419	2,779
Other derivative liabilities	170	181
Total financial liabilities measured at fair value	$ 170	$ 181