Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Relating to utility property, net	$ 475,517	$ 483,261
Regulatory assets recoverable through future rates	197,909	181,593
Other	12,674	15,117
Total deferred tax liabilities	686,100	679,971
Investment tax credit	3,216	3,855
Regulatory liabilities including ARO	229,025	220,491
Employee benefit plans	114,420	106,243
Other	8,389	10,573
Total deferred tax assets	355,050	341,162
Accumulated net deferred tax liability	331,050	338,809
Less: Net current deferred tax asset	(10,809)	(12,352)
Accumulated deferred income taxes - net	341,859	351,161
Indianapolis Power And Light Company [Member]
Relating to utility property, net	475,517	483,261
Regulatory assets recoverable through future rates	197,909	181,593
Other	12,643	15,288
Total deferred tax liabilities	686,069	680,142
Investment tax credit	3,216	3,855
Regulatory liabilities including ARO	229,025	220,491
Employee benefit plans	114,420	106,243
Other	8,276	10,366
Total deferred tax assets	354,937	340,955
Accumulated net deferred tax liability	(331,132)	(339,187)
Less: Net current deferred tax asset	(10,782)	(12,323)
Accumulated deferred income taxes - net	$ (341,914)	$ (351,510)