Utility Rate Cases (Narrative) (Details) (2012 Test Year Retail Electric Fuel Related Request Final Order [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	1 Months Ended
	Mar. 31, 2012	Dec. 31, 2011 WPL [Member]	Dec. 31, 2011 Cross State Air Pollution Rule [Member]
Utility Rate Cases [Line Items]
Increase in annual rates for its customers, amount		$ 4
Deferred compliance costs tolerance band			0.00%
Rate at which fuel costs will be monitored	2.00%