Regulatory Assets And Liabilities (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	$ 35,341,000	$ 33,912,000
Regulatory assets, noncurrent	378,904,000	450,710,000
Total regulatory assets	414,245,000	484,622,000
Regulatory liabilities, current	2,532,000	7,704,000
Regulatory liabilities, noncurrent	851,754,000	670,294,000
Total regulatory liabilities	854,286,000	677,998,000
Deferred Fuel Over/Under-Collection [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	0	3,311,000
Financial Transmission Rights [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	2,532,000	4,393,000
Asset Retirement Obligation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	696,973,000	668,787,000
Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	154,461,000	0
Unamortized Investment Tax Credit [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	320,000	1,507,000
Undercollections of rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	22,990,000	19,959,000
Amounts being recovered through base rates [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	12,351,000	13,953,000
Unrecognized Pension And Other Post Retirement Benefit Plan Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	205,573,000	218,070,000
Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	0	51,131,000
Regulatory liabilities, noncurrent	154,500,000
Deferred MISO Non-fuel Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	11,800,000.0
Regulatory assets, noncurrent	101,562,000
Unamortized Petersburg Unit 4 Carrying Charges And Certain Other Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	9,139,000	10,193,000
Unamortized Reacquisition Premium On Debt [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	21,109,000	22,501,000
Environmental Projects [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	40,434,000	30,678,000
Other Miscellaneous [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	1,087,000	3,778,000
Indianapolis Power And Light Company [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	35,341,000	33,912,000
Regulatory assets, noncurrent	378,904,000	450,710,000
Total regulatory assets	414,245,000	484,622,000
Regulatory liabilities, current	2,532,000	7,704,000
Regulatory liabilities, noncurrent	851,754,000	670,294,000
Total regulatory liabilities	854,286,000	677,998,000
Indianapolis Power And Light Company [Member] | Deferred Fuel Over/Under-Collection [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	0	3,311,000
Indianapolis Power And Light Company [Member] | Financial Transmission Rights [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	2,532,000	4,393,000
Indianapolis Power And Light Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	696,973,000	668,787,000
Indianapolis Power And Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	154,461,000	0
Indianapolis Power And Light Company [Member] | Unamortized Investment Tax Credit [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, noncurrent	320,000	1,507,000
Indianapolis Power And Light Company [Member] | Undercollections of rate riders [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	22,990,000	19,959,000
Indianapolis Power And Light Company [Member] | Amounts being recovered through base rates [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	12,351,000	13,953,000
Indianapolis Power And Light Company [Member] | Unrecognized Pension And Other Post Retirement Benefit Plan Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	205,573,000	218,070,000
Indianapolis Power And Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	0	51,131,000
Regulatory liabilities, noncurrent	154,500,000
Indianapolis Power And Light Company [Member] | Deferred MISO Non-fuel Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, current	11,800,000.0
Regulatory assets, noncurrent	101,562,000	114,359,000
Indianapolis Power And Light Company [Member] | Unamortized Petersburg Unit 4 Carrying Charges And Certain Other Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	9,139,000	10,193,000
Indianapolis Power And Light Company [Member] | Unamortized Reacquisition Premium On Debt [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	21,109,000	22,501,000
Indianapolis Power And Light Company [Member] | Environmental Projects [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	40,434,000	30,678,000
Indianapolis Power And Light Company [Member] | Other Miscellaneous [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, noncurrent	$ 1,087,000	$ 3,778,000