Leases (Schedule Of Lease Expenses Included In Consolidated Statements Of Income) (Details) - WPL [Member] - Sheboygan Falls Energy Facility [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Interest expense	$ 9.9	$ 10.4	$ 10.9
Depreciation and amortization	6.2	6.2	6.2
Total lease expenses included in income statements	$ 16.1	$ 16.6	$ 17.1