Benefit Plans (Carrying Value Of Entity's Deferred Compensation Obligations Interest And Equity Accounts) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Carrying value of deferred compensation obligations	$ 16.3	$ 20.5
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Carrying value of deferred compensation obligations	$ 5.0	$ 5.0