Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at January 1	$ 6,634	$ 7,147	$ 7,042
Gross increases - current period tax positions	470	724	962
Gross decreases - prior period tax positions	(2,453)	(1,237)	(857)
Unrecognized tax benefits at December 31	4,651	6,634	7,147
Indianapolis Power And Light Company [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at January 1	6,634	7,147	7,042
Gross increases - current period tax positions	470	724	962
Gross decreases - prior period tax positions	(2,453)	(1,237)	(857)
Unrecognized tax benefits at December 31	$ 4,651	$ 6,634	$ 7,147