Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Self-insured retention per occurrance	$ 5.0
Insurance expense	2.9	3.2	4.0
Prepaid insurance	1.5	1.5
Health coverage expense	22.8	22.6	21.0
Prepaid health coverage	2.4	2.1
Income taxes receivable	4.1
Income taxes payable		2.4
Deferred compensation arrangement vesting period	3 years
Deferred compensation arrangement holding period	2 years
Deferred compensation expense	0.8	1.2	1.7
Indianapolis Power And Light Company [Member]
Self-insured retention per occurrance	5.0
Insurance expense	2.9	3.2	4.0
Prepaid insurance	1.5	1.5
Health coverage expense	22.8	22.6	21.0
Prepaid health coverage	2.4	2.1
Income taxes receivable	5.0
Income taxes payable	0.9
Deferred compensation arrangement vesting period	3 years
Deferred compensation arrangement holding period	2 years
Deferred compensation expense	$ 0.8	$ 1.2	$ 1.7