Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) (IPL [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
IPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collections reinvested in receivables	$ 522.9	$ 482.3	$ 1,334.7	$ 1,367.8
Credit losses, net of recoveries	$ 3.0	$ 3.4	$ 7.3	$ 7.9