Quarterly Results (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
UTILITY OPERATING REVENUES	$ 311,536	$ 324,478	$ 292,659	$ 301,104	$ 282,266	$ 320,550	$ 279,943	$ 289,165	$ 1,229,777	$ 1,171,924	$ 1,144,903
Utility operating income	40,139	50,227	34,583	37,951	32,339	48,451	36,137	35,726	162,900	152,653	172,438
Net income	16,135	27,541	12,291	16,029	8,491	26,120	12,534	13,430	71,996	60,575	79,947
Indianapolis Power And Light Company [Member]
UTILITY OPERATING REVENUES	311,536	324,478	292,659	301,104	282,266	320,550	279,943	289,165	1,229,777	1,171,924	1,144,903
Utility operating income	40,139	50,227	34,583	37,951	32,339	48,451	36,137	35,726	162,900	152,653	172,438
Net income	$ 24,564	$ 35,505	$ 20,316	$ 23,744	$ 16,852	$ 34,810	$ 30,547	$ 23,189	$ 104,129	$ 105,398	$ 119,788