Pension And Other Postretirement Benefits (Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended					1 Months Ended	12 Months Ended					1 Months Ended	12 Months Ended			1 Months Ended	5 Months Ended		7 Months Ended		12 Months Ended			1 Months Ended	5 Months Ended		7 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Jan. 31, 2013 Indianapolis Power And Light Company [Member]	Dec. 31, 2012 Indianapolis Power And Light Company [Member]		Dec. 31, 2011 Indianapolis Power And Light Company [Member]		Dec. 31, 2010 Indianapolis Power And Light Company [Member]	Jan. 31, 2013 Defined Benefit Pension Benefit [Member]	Dec. 31, 2012 Defined Benefit Pension Benefit [Member]	Dec. 31, 2011 Defined Benefit Pension Benefit [Member]	Dec. 31, 2010 Defined Benefit Pension Benefit [Member]	Jan. 31, 2013 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]	May 31, 2010 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]		Dec. 31, 2010 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]		Dec. 31, 2012 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]	Dec. 31, 2011 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]	Dec. 31, 2010 Defined Benefit Pension Benefit [Member] Indianapolis Power And Light Company [Member]	Jan. 31, 2013 Supplemental Retirement Plan [Member]	May 30, 2010 Supplemental Retirement Plan [Member]		Dec. 31, 2010 Supplemental Retirement Plan [Member]		Dec. 31, 2012 Supplemental Retirement Plan [Member]	Dec. 31, 2011 Supplemental Retirement Plan [Member]	Dec. 31, 2010 Supplemental Retirement Plan [Member]	Jan. 31, 2013 Supplemental Retirement Plan [Member] Indianapolis Power And Light Company [Member]	Dec. 31, 2012 Supplemental Retirement Plan [Member] Indianapolis Power And Light Company [Member]	Dec. 31, 2011 Supplemental Retirement Plan [Member] Indianapolis Power And Light Company [Member]	Dec. 31, 2010 Supplemental Retirement Plan [Member] Indianapolis Power And Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 7,986		$ 7,234		$ 6,590		$ 7,986		$ 7,234		$ 6,590
Interest Cost		30,232		31,828		31,577		30,232		31,828		31,577
Plan settlements						204						204
Expected return on assets		(32,554)		(32,168)		(29,250)		(32,554)		(32,168)		(29,250)
Amortization of prior service cost		4,246	[1]	4,346	[1]	3,476		4,246	[1]	4,346	[1]	3,476
Recognized actuarial loss		19,471	[1]	13,306	[1]	11,838		19,471	[1]	13,306	[1]	11,838
Net periodic benefit cost		29,381		24,546		24,435		29,381		24,546		24,435
Less: amounts capitalized		2,497		2,258		2,321		2,497		2,258		2,321
Amount charged to expense		$ 26,884		$ 22,288		$ 22,114		$ 26,884		$ 22,288		$ 22,114
Discount rate													3.80%	4.56%	5.38%	5.93%	3.80%	5.27%	[2]	5.08%	[2]	4.56%	5.38%	5.93%	3.41%	5.27%	[3]	5.08%	[3]	4.37%	5.09%		3.41%	4.37%	5.09%
Expected return on plan assets	7.25%	7.50%					7.25%	7.50%						7.50%	7.75%	8.00%						7.50%	7.75%	8.00%						7.50%	7.75%	8.00%		7.50%	7.75%	8.00%

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

[2] 5.27% for the period January 1, 2010 thru May 31, 2010, 5.08% for the settlement on May 31, 2010 and the period June 1, 2010 through December 31, 2010.

[3] 5.27% for the period January 1, 2010 thru May 31, 2010, 5.08% for the settlement on May 31, 2010 and the period June 1, 2010 through December 31, 2010.