Benefit Plans (Schedule Of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)	$ 731,825	$ 723,887
Service cost	7,344	7,018	$ 8,314
Interest cost	25,305	25,815	29,638
Actuarial (gain) loss	52,451	9,718
Amendments (primarily increases in pension bands)	900	0
Settlements	266	0
Benefits paid	(35,451)	(34,613)
Projected benefit obligation at ending Measurement Date	782,108	731,825	723,887
Change in plan assets:
Fair value of plan assets at beginning Measurement Date	674,430	647,573
Actual return on plan assets	93,022	45,520
Employer contributions during quarter	7,212	15,950	25,200
Benefits paid	(35,451)	(34,613)
Fair value of plan assets at ending Measurement Date	738,947	674,430	647,573
Unfunded status	(43,161)	(57,395)
Amounts recognized in the statement of financial position under ASC 715:
Noncurrent liabilities	(43,161)	(57,395)
Net amount recognized	(43,161)	(57,395)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period	900	0
Net loss (gain) arising during period	4,101	7,690
Amortization of prior service cost	(4,240)	(5,183)	(4,867)
Amortization of gain (loss)	(13,341)	(13,896)
Total recognized in regulatory assets	(12,580)	(11,389)
Net loss (gain)	193,807	203,047
Prior service cost (credit)	17,318	20,658
Total amounts included in regulatory assets (liabilities)	211,125	223,705
Indianapolis Power And Light Company [Member]
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)	731,825
Service cost	7,344	7,018	8,314
Interest cost	25,305	25,815	29,638
Actuarial (gain) loss	52,451	9,718
Amendments (primarily increases in pension bands)	900	0
Settlements	266	0
Benefits paid	(35,451)	(34,613)
Projected benefit obligation at ending Measurement Date	782,108	731,825
Change in plan assets:
Fair value of plan assets at beginning Measurement Date	674,430
Actual return on plan assets	93,022	45,520
Employer contributions during quarter	7,212	15,950	25,200
Benefits paid	(35,451)	(34,613)
Fair value of plan assets at ending Measurement Date	738,947	674,430
Unfunded status	(43,161)	(57,395)
Amounts recognized in the statement of financial position under ASC 715:
Noncurrent liabilities	(43,161)	(57,395)
Net amount recognized	(43,161)	(57,395)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period	900	0
Net loss (gain) arising during period	4,101	7,690
Amortization of prior service cost	(4,240)	(5,183)	$ (4,867)
Amortization of gain (loss)	(13,341)	(13,896)
Total recognized in regulatory assets	(12,580)	(11,389)
Net loss (gain)	193,807	203,047
Prior service cost (credit)	17,318	20,658
Total amounts included in regulatory assets (liabilities)	$ 211,125	$ 223,705