Income Taxes (Schedule Of Uncertain Tax Positions Balances In Regulatory Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Tax positions favorably impacting future effective tax rates for continuing operations	$ 0.7	$ 0	$ 0
Interest accrued	0	0.4	0.7
IPL [Member]
Tax positions favorably impacting future effective tax rates for continuing operations	0	0	0
Interest accrued	0	0.4	0.7
WPL [Member]
Tax positions favorably impacting future effective tax rates for continuing operations	0.7	0	0
Interest accrued	$ 0	$ 0	$ 0

This element represents the amount of interest expense accrued as of the date of the statement of financial position for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

+ References+ Details