Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Self-insured retention per occurrence	$ 5.0
Insurance expense	3.1	$ 3.1	$ 2.7
Prepaid insurance	1.9	2.0
Health coverage expense	24.9	23.2	24.5
Income taxes receivable	14.7	2.1
Deferred compensation expense	0.8	0.9	0.7
Billings from related party	2.4	3.9	2.4
Service Company [Member]
Related Party Transaction [Line Items]
Costs incurred by related party	34.4	27.4	23.2
Prepaid balance to related party	3.1	3.4
Director [Member]
Related Party Transaction [Line Items]
Billings from related party		198.5	232.0
Accounts payable to related vendor		2.3
Ipalco Enterprises, Inc. [Member]
Related Party Transaction [Line Items]
Costs incurred by related party	10.7	9.2	7.5
Indianapolis Power And Light Company [Member]
Related Party Transaction [Line Items]
Self-insured retention per occurrence	5.0
Insurance expense	3.1	3.1	2.7
Prepaid insurance	1.9	2.0
Health coverage expense	24.9	23.2	24.5
Income taxes receivable	17.0	1.0
Deferred compensation expense	0.8	0.9	0.7
Costs incurred by related party	10.7	9.2	7.5
Prepaid balance to related party	3.1	3.4
Billings from related party	2.4	3.9	2.4
Indianapolis Power And Light Company [Member] | Service Company [Member]
Related Party Transaction [Line Items]
Costs incurred by related party	$ 34.1	26.9	22.6
Indianapolis Power And Light Company [Member] | Director [Member]
Related Party Transaction [Line Items]
Billings from related party		198.5	$ 232.0
Accounts payable to related vendor		$ 2.3