Regulatory Assets And Liabilities (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	$ 37,398	$ 28,399
Regulatory assets, noncurrent	355,614	395,077
Total regulatory assets	393,012	423,476
Regulatory liabilities, current	52,654	51,024
Regulatory Liability, Noncurrent	846,430	870,255
Total regulatory liabilities	899,084	921,279
Overcollection and other credits passed to customers through rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	51,790	47,925
Financial Transmission Rights [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	864	3,099
Asset Retirement Obligation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	719,680	707,662
Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent		141,058
Unamortized Investment Tax Credit [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	3,337	21,341
Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	1,257	194
Undercollections of rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	22,216	13,217
Amounts being recovered through base rates [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	15,182	15,182
Unrecognized Pension And Other Post Retirement Benefit Plan Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	176,646	195,559
Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	122,156	141,100
Deferred MISO Non-fuel Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	74,660
Unamortized Petersburg Unit 4 Carrying Charges And Certain Other Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	7,030	8,084
Unamortized Reacquisition Premium On Debt [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	18,330	19,714
Environmental Projects [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	78,021	81,204
Other Miscellaneous [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	927	2,464
Indianapolis Power And Light Company
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	37,398	28,399
Regulatory assets, noncurrent	355,614	395,077
Total regulatory assets	393,012	423,476
Regulatory liabilities, current	52,654	51,024
Regulatory Liability, Noncurrent	846,430	870,255
Total regulatory liabilities	899,084	921,279
Indianapolis Power And Light Company | Overcollection and other credits passed to customers through rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	51,790	47,925
Indianapolis Power And Light Company | Financial Transmission Rights [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	864	3,099
Indianapolis Power And Light Company | Asset Retirement Obligation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	719,680	707,662
Indianapolis Power And Light Company | Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent		141,058
Indianapolis Power And Light Company | Unamortized Investment Tax Credit [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	3,337	21,341
Indianapolis Power And Light Company | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	1,257	194
Indianapolis Power And Light Company | Undercollections of rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	22,216	13,217
Indianapolis Power And Light Company | Amounts being recovered through base rates [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	15,182	15,182
Indianapolis Power And Light Company | Unrecognized Pension And Other Post Retirement Benefit Plan Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	176,646	195,559
Indianapolis Power And Light Company | Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory Liability, Noncurrent	122,156	141,100
Indianapolis Power And Light Company | Deferred MISO Non-fuel Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	74,660
Indianapolis Power And Light Company | Unamortized Petersburg Unit 4 Carrying Charges And Certain Other Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	7,030	8,084
Indianapolis Power And Light Company | Unamortized Reacquisition Premium On Debt [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	18,330	19,714
Indianapolis Power And Light Company | Environmental Projects [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	78,021	81,204
Indianapolis Power And Light Company | Other Miscellaneous [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	$ 927	$ 2,464