Income Taxes (Narrative) (Details) - USD ($)		3 Months Ended		12 Months Ended
	Mar. 25, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Entity Information [Line Items]
Income taxes					$ 29,600,000	$ 28,275,000	$ 65,050,000
Additional reduction to the state corporate income tax rate	1.60%
Reduction to the state corporate income tax rate	2.00%
Decrease in deferred taxes					1,300,000
Tax benefit from temporary differences					$ 100,000
Statutory state income tax rate					5.625%
Income tax expense (benefit) from qualifying production activity							$ 3,900,000
Tax Cuts and Jobs Act of 2017, change in income tax expense (benefit)		$ 0.0	$ 200,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					21.00%	21.00%	35.00%
Tax Cuts and Jobs Act of 2017, change in deferred tax liability		215,500,000			$ 7,700,000	$ 215,500,000
Indianapolis Power And Light Company
Entity Information [Line Items]
Income taxes					37,400,000	$ 33,750,000	$ 87,000,000
Additional reduction to the state corporate income tax rate	1.60%
Reduction to the state corporate income tax rate	2.00%
Decrease in deferred taxes					1,300,000
Tax benefit from temporary differences					$ 100,000
Statutory state income tax rate						5.625%
Percentage of qualifying production activity eligible for deduction					9.00%
Income tax expense (benefit) from qualifying production activity							$ 4,800,000
Tax Cuts and Jobs Act of 2017, change in income tax expense (benefit)		0.0	$ 200,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					21.00%	21.00%	35.00%
Effective Income Tax Rate Reconciliation Tax Cuts and Jobs Act of 2017 Percent						21.00%
Tax Cuts and Jobs Act of 2017, change in deferred tax liability		$ 215,500,000			$ 7,700,000	$ 215,500,000
Scenario, Forecast [Member]
Entity Information [Line Items]
Statutory state income tax rate				5.375%
Scenario, Forecast [Member] | Indianapolis Power And Light Company
Entity Information [Line Items]
Statutory state income tax rate				5.375%