Segment Information (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Long-term debt	$ 1,761,120,000	$ 1,760,316,000
Cash	6,400,000	6,700,000
Long-term nonutility investments	4,700,000	4,600,000
Nonutility assets representation rate, percentage	1.00%	1.00%
Ipalco Enterprises, Inc. [Member]
Debt Instrument [Line Items]
Long-term debt	796,916,000	796,141,000
7.250% Senior Secured Notes [Member] | Ipalco Enterprises, Inc. [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	7.25%
Debt instrument, maturity date	Apr. 01, 2016
Long-term debt	$ 400,000,000	$ 400,000,000