Regulatory Assets And Liabilities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	$ 2,532	$ 7,704
Regulatory assets, current	35,341	33,912
Regulatory assets	$ 378,904	$ 450,710
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	35.00%	35.00%
Regulatory liabilities	$ 851,754	$ 670,294
Deferred Fuel Over/Under-Collection [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	0	3,311
Indianapolis Power And Light Company [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	2,532	7,704
Regulatory assets, current	35,341	33,912
Regulatory assets	$ 378,904	$ 450,710
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation Tax Cuts and Jobs Act of 2017 Percent	21.00%
Regulatory liabilities	$ 851,754	$ 670,294
Indianapolis Power And Light Company [Member] | Deferred Fuel Over/Under-Collection [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities, current	$ 0	3,311
Minimum [Member]
Regulatory Assets And Liabilities [Line Items]
Amortization period of regulatory assets	1 year
Minimum [Member] | Indianapolis Power And Light Company [Member]
Regulatory Assets And Liabilities [Line Items]
Amortization period of regulatory assets	1 year
Maximum [Member]
Regulatory Assets And Liabilities [Line Items]
Amortization period of regulatory assets	35 years
Maximum [Member] | Indianapolis Power And Light Company [Member]
Regulatory Assets And Liabilities [Line Items]
Amortization period of regulatory assets	35 years
Deferred Income Tax Charge [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 0	51,131
Regulatory liabilities	154,500
Deferred Income Tax Charge [Member] | Indianapolis Power And Light Company [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	0	51,131
Regulatory liabilities	$ 154,500
Deferred Project Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets		$ 114,359