Fair Value (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Entity Information [Line Items]
Debt Issuance Costs, Net	$ 24,400	$ 22,200
Unamortized debt discount	6,900	6,800
Asset retirement obligations	79,535	80,568
Indianapolis Power And Light Company [Member]
Entity Information [Line Items]
Debt Issuance Costs, Net	16,500	17,200
Unamortized debt discount	6,353	6,477
Asset retirement obligations	$ 79,535	$ 80,568