Fair Value Measurements (Reconciliation Of Financial Instruments Classified As Level 3) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,	$ 2,598	$ 34,208
Unrealized losses recognized in OCI		331
Unrealized losses recognized in earnings	11	(15)
Unrealized loss recognized as a regulatory liability		(5,095)
Issuances	8,832	8,085
Settlements	(9,192)	(34,916)
Balance at,	2,249	2,598
Derivative Financial Instruments, net Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,	2,598	(7,461)
Unrealized losses recognized in earnings	11	(15)
Unrealized loss recognized as a regulatory liability		(5,095)
Issuances	8,832	8,085
Settlements	(9,192)	7,084
Balance at,	2,249	2,598
Mutual Fund - Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,		41,669
Unrealized losses recognized in OCI		331
Settlements		(42,000)
Indianapolis Power And Light Company [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,	2,598	34,208
Unrealized losses recognized in OCI		331
Unrealized losses recognized in earnings	11	(15)
Unrealized loss recognized as a regulatory liability		(5,095)
Issuances	8,832	8,085
Settlements	(9,192)	(34,916)
Balance at,	2,249	2,598
Indianapolis Power And Light Company [Member] | Derivative Financial Instruments, net Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,	2,598	(7,461)
Unrealized losses recognized in earnings	11	(15)
Unrealized loss recognized as a regulatory liability		(5,095)
Issuances	8,832	8,085
Settlements	(9,192)	7,084
Balance at,	2,249	2,598
Indianapolis Power And Light Company [Member] | Mutual Fund - Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at,		41,669
Unrealized losses recognized in OCI		331
Settlements		$ (42,000)