Pension And Other Postretirement Benefits (Schedule Of Defined Benefit Plans Disclosures) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)	$ 679,261		$ 607,408
Service Cost	7,986		7,234		6,590
Interest Cost	30,232		31,828		31,577
Plan settlements					204
Actuarial (gain) loss	69,099		62,587
Amendments (primarily increases in pension bands)	7,349		82
Benefits paid	(30,327)		(29,878)
Projected benefit obligation at ending Measurement Date	763,600		679,261		607,408
Change in plan assets:
Fair value of plan assets at beginning Measurement Date	426,384		412,611
Actual return on plan assets	50,713		6,305
Employer contributions	48,312		37,345		28,700
Benefits paid	(30,327)		(29,877)
Fair value of plan assets at ending Measurement Date	495,082		426,384		412,611
Funded status	(268,518)		(252,877)
Amounts recognized in the statement of financial position under ASC 715:
Current liabilities
Noncurrent liabilities	(268,518)		(252,877)
Net amount recognized	(268,518)		(252,877)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period	7,350	[1]	82	[1]
Net loss (gain) arising during period	50,938	[1]	88,450	[1]
Amortization of prior service cost	(4,246)	[1]	(4,346)	[1]	(3,476)
Amortization of gain (loss)	(19,471)	[1]	(13,306)	[1]	(11,838)
Total recognized in regulatory assets	34,571	[1]	70,880	[1]
Total amounts included in accumulated other comprehensive income (loss)	(1)	[1]	(1)	[1]
Net loss (gain)	314,557	[1]	283,089	[1]
Prior service cost (credit)	33,836	[1]	30,732	[1]
Total amounts included in regulatory assets (liabilities)	348,393		313,821
Indianapolis Power And Light Company [Member]
Change in benefit obligation:
Projected benefit obligation at beginning Measurement Date (see below)	679,261		607,408
Service Cost	7,986		7,234		6,590
Interest Cost	30,232		31,828		31,577
Plan settlements					204
Actuarial (gain) loss	69,099		62,587
Amendments (primarily increases in pension bands)	7,349		82
Benefits paid	(30,327)		(29,878)
Projected benefit obligation at ending Measurement Date	763,600		679,261		607,408
Change in plan assets:
Fair value of plan assets at beginning Measurement Date	426,384		412,611
Actual return on plan assets	50,713		6,305
Employer contributions	48,312		37,345		28,700
Benefits paid	(30,327)		(29,877)
Fair value of plan assets at ending Measurement Date	495,082		426,384		412,611
Funded status	(268,518)		(252,877)
Amounts recognized in the statement of financial position under ASC 715:
Current liabilities
Noncurrent liabilities	(268,518)		(252,877)
Net amount recognized	(268,518)		(252,877)
Sources of change in regulatory assets(1):
Prior service cost (credit) arising during period	7,350	[1]	82	[1]
Net loss (gain) arising during period	50,938	[1]	88,450	[1]
Amortization of prior service cost	(4,246)	[1]	(4,346)	[1]	(3,476)
Amortization of gain (loss)	(19,471)	[1]	(13,306)	[1]	(11,838)
Total recognized in regulatory assets	34,571	[1]	70,880	[1]
Total amounts included in accumulated other comprehensive income (loss)	(1)	[1]	(1)	[1]
Net loss (gain)	314,557	[1]	283,089	[1]
Prior service cost (credit)	33,836	[1]	30,732	[1]
Total amounts included in regulatory assets (liabilities)	$ 348,393		$ 313,821

[1] Represents amounts included in regulatory assets (liabilities) yet to be recognized as components of net prepaid (accrued) benefit costs.