Benefit Plans (Schedule Of Qualified and Non-qualified Pension And Other Postretirement Benefits Costs (Credits)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits Costs [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	$ 0.3	$ 0.5	$ 0.7	$ 1.0
Pension Benefits Costs [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	0.2	0.4	0.5	0.7
OPEB Costs (Credits) [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	(0.1)	0	(0.2)	(0.1)
OPEB Costs (Credits) [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits costs (credits) associated with Corporate Services employees	$ (0.1)	$ (0.1)	$ (0.1)	$ (0.1)