Benefit Plans (Schedule Of Qualified And Non-Qualified Pension And Other Post Retirement Benefits Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated qualified and non-qualified costs (credits)	$ 4.8	[1]	$ 4.9	[1]	$ 5.8	[1]
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated qualified and non-qualified costs (credits)	3.6	[1]	3.6	[1]	4.2	[1]
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated qualified and non-qualified costs (credits)	(0.3)		0.1		0.3
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Allocated qualified and non-qualified costs (credits)	$ (0.2)		$ 0.1		$ 0.2

[1] Refer to IPL’s and WPL’s “Net Periodic Benefit Costs (Credits)” tables above for additional benefits costs related to the Cash Balance Plan allocated to IPL and WPL by Corporate Services in 2013 and 2011.