Leases (Schedule Of Operating Leases) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases [Line Items]
Operating lease rental expenses (excluding contingent rentals)	$ 12	$ 9	$ 69
Contingent rentals (primarily related to the Riverside PPA)	0	0	6
Total operating lease rental expenses	12us-gaap_OperatingLeasesRentExpenseNet	9us-gaap_OperatingLeasesRentExpenseNet	75us-gaap_OperatingLeasesRentExpenseNet
IPL [Member]
Leases [Line Items]
Operating lease rental expenses (excluding contingent rentals)	4	4	4
Contingent rentals (primarily related to the Riverside PPA)	0	0	0
Total operating lease rental expenses	4	4	4
WPL [Member]
Leases [Line Items]
Operating lease rental expenses (excluding contingent rentals)	7	5	64
Contingent rentals (primarily related to the Riverside PPA)	0	0	5
Total operating lease rental expenses	$ 7	$ 5	$ 69

- Definition

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

+ References+ Details