Rate Matters (Details) (Public Service Commission of Wisconsin (PSCW) [Member], USD $) In Millions, unless otherwise specified	May 31, 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
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%