Rate Matters (Details) (Public Service Commission of Wisconsin (PSCW) [Member], USD $) In Millions, unless otherwise specified	Oct. 19, 2012	Jun. 30, 2012
Electric Rate Case [Member]
Rate Matters [Abstract]
Entity's original requested rate increase (decrease) for 2013		$ 39.1
Percentage increase in entity's original requested rate increase for 2013 (in hundredths)		6.70%
Entity's original requested percent return on equity (in hundredths)		10.40%
Entity's original requested equity ratio percent (in hundredths)		52.50%
Entity's rate base in original requested rate increase (decrease)		788.6
Entity's rate increase (decrease) requested by third party/parties	32.9
Entity's percentage increase in rate increase (decrease) requested by third party/parties (in hundredths)	5.60%
Entity's percent return on equity requested by third party/parties (in hundredths)	10.40%
Entity's equity ratio percent requested by third party/parties (in hundredths)	52.50%
Adjustment to entity's requested rate increase related to employee compensation expense requested by third party/parties	(2.2)
Adjustment to entity's requested rate increase related to electric fuel expense and fixed production charges requested by third party/parties	(2.9)
Gas Rate Case [Member]
Rate Matters [Abstract]
Entity's original requested rate increase (decrease) for 2013		$ 5.3
Percentage increase in entity's original requested rate increase for 2013 (in hundredths)		4.90%