Benefit Plans (Schedule Of Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 7,344	$ 7,018	$ 8,314
Interest cost		25,305	25,815	29,638
Expected return on assets		(44,672)	(43,492)	(44,819)
Amortization of prior service cost		4,240	5,183	4,867
Recognized actuarial loss		13,195	13,896	13,890
Recognized settlement loss		146	0	206
Net periodic benefit cost		5,558	8,420	12,096
Less: amounts capitalized		845	1,187	1,403
Amount charged to expense		$ 4,713	7,233	10,693
Expected return on plan assets		6.75%
Indianapolis Power And Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 7,344	7,018	8,314
Interest cost		25,305	25,815	29,638
Expected return on assets		(44,672)	(43,492)	(44,819)
Amortization of prior service cost		4,240	5,183	4,867
Recognized actuarial loss		13,195	13,896	13,890
Recognized settlement loss		146	0	206
Net periodic benefit cost		5,558	8,420	12,096
Less: amounts capitalized		845	1,187	1,403
Amount charged to expense		$ 4,713	$ 7,233	$ 10,693
Expected return on plan assets		6.75%
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.67%	4.29%	4.42%	4.06%
Expected return on plan assets		6.75%	6.75%	6.75%
Pension Benefit [Member] | Indianapolis Power And Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.67%	4.29%	4.42%	4.06%
Expected return on plan assets		6.75%	6.75%	6.75%
Supplemental Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.60%	4.00%	4.19%	3.82%
Expected return on plan assets		6.75%	6.75%	6.75%
Supplemental Retirement Plan [Member] | Indianapolis Power And Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.60%	4.00%	4.19%	3.82%
Expected return on plan assets		6.75%	6.75%	6.75%