Benefit Plans (Schedule Of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)	$ 782,108	$ 697,228	$ 782,108
Service cost		7,412	8,450	$ 7,344
Interest cost		27,343	25,220	25,305
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		88,311	(62,303)
Amendments (primarily increases in pension bands)		0	5,446
Settlements	(1,200)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		0	450
Benefits paid		(37,499)	(62,143)
Projected benefit obligation at ending Measurement Date		782,795	697,228	782,108
Change in plan assets:
Fair value of plan assets at beginning Measurement Date	738,947	684,485	738,947
Actual return on plan assets		122,690	(22,404)
Employer contributions during quarter		28	30,085	7,200
Benefits paid		(37,499)	(62,143)
Fair value of plan assets at ending Measurement Date		769,704	684,485	738,947
Unfunded status		(13,091)	(12,743)
Amounts recognized in the statement of financial position under ASC 715:
Noncurrent liabilities		(13,091)	(12,743)
Net amount recognized		(13,091)	(12,743)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period		0	5,446
Net loss (gain) arising during period		(4,472)	902
Amortization of prior service cost		(3,823)	(4,618)
Amortization of gain (loss)		(11,084)	(11,403)
Total recognized in regulatory assets		(19,379)	(9,673)
Net loss (gain)		167,750	183,306
Prior service cost (credit)		14,323	18,146
Total amounts included in regulatory assets (liabilities)		182,073	201,452
Indianapolis Power And Light Company
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)		697,228
Service cost		7,412	8,450	7,344
Interest cost		27,343	25,220	25,305
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		88,311	(62,303)
Amendments (primarily increases in pension bands)		0	5,446
Settlements	$ (1,200)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		0	450
Benefits paid		(37,499)	(62,143)
Projected benefit obligation at ending Measurement Date		782,795	697,228
Change in plan assets:
Fair value of plan assets at beginning Measurement Date		684,485
Actual return on plan assets		122,690	(22,404)
Employer contributions during quarter		28	30,085	$ 7,200
Benefits paid		(37,499)	(62,143)
Fair value of plan assets at ending Measurement Date		769,704	684,485
Unfunded status		(13,091)	(12,743)
Amounts recognized in the statement of financial position under ASC 715:
Noncurrent liabilities		(13,091)	(12,743)
Net amount recognized		(13,091)	(12,743)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period		0	5,446
Net loss (gain) arising during period		(4,472)	902
Amortization of prior service cost		(3,823)	(4,618)
Amortization of gain (loss)		(11,084)	(11,403)
Total recognized in regulatory assets		(19,379)	(9,673)
Net loss (gain)		167,750	183,306
Prior service cost (credit)		14,323	18,146
Total amounts included in regulatory assets (liabilities)		182,073	201,452
US Treasury Securities [Member]
Change in plan assets:
Fair value of plan assets at beginning Measurement Date		129,305
Fair value of plan assets at ending Measurement Date			129,305
US Treasury Securities [Member] | Indianapolis Power And Light Company
Change in plan assets:
Fair value of plan assets at beginning Measurement Date		$ 129,305
Fair value of plan assets at ending Measurement Date			$ 129,305