Fair Value Measurements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 6,400,000	$ 5,900,000
Recorded amount of auction rate securities			1,700,000
Aggregate principal amount	1,815,300,000	1,829,300,000
Customer deposits	24,800,000	23,100,000
Unamortized discount - net	4,200,000	5,000,000
Impairments recorded on investments	0	1,600,000	1,200,000
Recorded value for investment	1,900,000	1,900,000
Ipalco Enterprises, Inc. [Member]
Unamortized discount - net	3,084,000	3,859,000
Indianapolis Power And Light Company [Member]
Cash and cash equivalents	400,000	500,000
Recorded amount of auction rate securities			1,700,000
Aggregate principal amount	1,015,300,000	1,029,300,000
Customer deposits	24,800,000	23,100,000
Unamortized discount - net	1,096,000	1,125,000
Auction Rate Securities [Member]
Aggregate principal amount			2,000,000
Auction Rate Securities [Member] | Indianapolis Power And Light Company [Member]
Aggregate principal amount			2,000,000
1995B Series Bonds [Member]
Aggregate principal amount			40,000,000
1995B Series Bonds [Member] | Indianapolis Power And Light Company [Member]
Aggregate principal amount			$ 40,000,000