Benefit Plans (Information For Pension Plans With A Benefit Obligation In Excess Of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Entity Information [Line Items]
Benefit obligation	$ 782,108	$ 731,825
Plan assets	738,947	674,430
Benefit obligation in excess of plan assets	43,161	57,395
Indianapolis Power And Light Company [Member]
Entity Information [Line Items]
Benefit obligation	782,108	731,825
Plan assets	738,947	674,430
Benefit obligation in excess of plan assets	$ 43,161	$ 57,395