Benefit Plans (Information For Pension Plans With An Accumulated Benefit Obligation In Excess Of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Entity Information [Line Items]
Accumulated benefit obligation	$ 769,678	$ 720,901
Plan assets	738,947	674,430
Accumulated benefit obligation in excess of plan assets	30,731	46,471
Indianapolis Power And Light Company [Member]
Entity Information [Line Items]
Accumulated benefit obligation	769,678	720,901
Plan assets	738,947	674,430
Accumulated benefit obligation in excess of plan assets	$ 30,731	$ 46,471