Pension And Other Postretirement Benefits (Schedule Of Fair Value Of Pension Plan Assets) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	$ 495,082,000	$ 426,384,000		$ 412,611,000
Percentage by asset category	100.00%	100.00%
Transfer of pension assets from Level 1 to Level 2	20,600,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	240,940,000	205,687,000
Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	254,142,000	220,697,000
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	42,139,000	14,984,000
Percentage by asset category	9.00%	4.00%
Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	42,139,000	14,984,000
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	96,347,000	99,152,000
Percentage by asset category	19.00%	23.00%
Common Stock [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	96,347,000	99,152,000
Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		718,000
Percentage by asset category		0.00%
Preferred Stock [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		718,000
REIT [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	22,330,000	20,340,000
Percentage by asset category	5.00%	5.00%
REIT [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	22,330,000	20,340,000
Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	25,170,000	30,542,000
Percentage by asset category	5.00%	7.00%
Government Debt Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	25,170,000	30,542,000
Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	148,553,000	77,838,000
Percentage by asset category	30.00%	18.00%
Corporate Debt Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	148,553,000	77,838,000
Other Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		49,650,000
Percentage by asset category		12.00%
Other Debt Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		49,650,000
Mutual Fund - Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	51,154,000	38,054,000
Percentage by asset category	10.00%	9.00%
Mutual Fund - Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	51,154,000	38,054,000
Mutual Fund - Debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	3,626,000	1,748,000
Percentage by asset category	1.00%	0.00%
Mutual Fund - Debt [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	3,626,000	1,748,000
Mutual Fund - REIT [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	174,000	149,000
Percentage by asset category	0.00%	0.00%
Mutual Fund - REIT [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	174,000	149,000
Hedge Funds - Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	35,498,000	32,432,000
Percentage by asset category	7.00%	8.00%
Hedge Funds - Equity [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	35,498,000	32,432,000
Common/Collective Trust Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	70,091,000	60,777,000	[1]
Percentage by asset category	14.00%	14.00%	[1]
Common/Collective Trust Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	70,091,000	60,777,000	[1]
Indianapolis Power And Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	495,082,000	426,384,000		412,611,000
Percentage by asset category	100.00%	100.00%
Transfer of pension assets from Level 1 to Level 2	20,600,000
Indianapolis Power And Light Company [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	240,940,000	205,687,000
Indianapolis Power And Light Company [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	254,142,000	220,697,000
Indianapolis Power And Light Company [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	42,139,000	14,984,000
Percentage by asset category	9.00%	4.00%
Indianapolis Power And Light Company [Member] | Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	42,139,000	14,984,000
Indianapolis Power And Light Company [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	96,347,000	99,152,000
Percentage by asset category	19.00%	23.00%
Indianapolis Power And Light Company [Member] | Common Stock [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	96,347,000	99,152,000
Indianapolis Power And Light Company [Member] | Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		718,000
Percentage by asset category		0.00%
Indianapolis Power And Light Company [Member] | Preferred Stock [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		718,000
Indianapolis Power And Light Company [Member] | REIT [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	22,330,000	20,340,000
Percentage by asset category	5.00%	5.00%
Indianapolis Power And Light Company [Member] | REIT [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	22,330,000	20,340,000
Indianapolis Power And Light Company [Member] | Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	25,170,000	30,542,000
Percentage by asset category	5.00%	7.00%
Indianapolis Power And Light Company [Member] | Government Debt Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	25,170,000	30,542,000
Indianapolis Power And Light Company [Member] | Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	148,553,000	77,838,000
Percentage by asset category	30.00%	18.00%
Indianapolis Power And Light Company [Member] | Corporate Debt Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	148,553,000	77,838,000
Indianapolis Power And Light Company [Member] | Other Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		49,650,000
Percentage by asset category		12.00%
Indianapolis Power And Light Company [Member] | Other Debt Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets		49,650,000
Indianapolis Power And Light Company [Member] | Mutual Fund - Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	51,154,000	38,054,000
Percentage by asset category	10.00%	9.00%
Indianapolis Power And Light Company [Member] | Mutual Fund - Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	51,154,000	38,054,000
Indianapolis Power And Light Company [Member] | Mutual Fund - Debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	3,626,000	1,748,000
Percentage by asset category	1.00%	0.00%
Indianapolis Power And Light Company [Member] | Mutual Fund - Debt [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	3,626,000	1,748,000
Indianapolis Power And Light Company [Member] | Mutual Fund - REIT [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	174,000	149,000
Percentage by asset category	0.00%	0.00%
Indianapolis Power And Light Company [Member] | Mutual Fund - REIT [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	174,000	149,000
Indianapolis Power And Light Company [Member] | Hedge Funds - Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	35,498,000	32,432,000
Percentage by asset category	7.00%	8.00%
Indianapolis Power And Light Company [Member] | Hedge Funds - Equity [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	35,498,000	32,432,000
Indianapolis Power And Light Company [Member] | Common/Collective Trust Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	70,091,000	60,777,000	[1]
Percentage by asset category	14.00%	14.00%	[1]
Indianapolis Power And Light Company [Member] | Common/Collective Trust Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of benefit plan assets	$ 70,091,000	$ 60,777,000	[1]

[1] On January 26, 2011, we transferred Level 1 securities with a fair value of $20.6 million to a common/collective trust fund. This resulted in a transfer of $20.6 million from Level 1 to Level 2 because the fair value of the interest in the common/collective fund is classified as Level 2 within the fair value hierarchy.