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, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Interest expense	$ 8	$ 9	$ 9
Depreciation and amortization	6	6	6
Total lease expenses included in income statements	$ 14	$ 15	$ 15