Columbia Environmental Project Construction (Details) (USD $)			3 Months Ended			3 Months Ended			12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 MGE [Member]	Mar. 31, 2013 MGE [Member]	Dec. 31, 2013 MGE [Member]	Mar. 31, 2014 MGE [Member] Columbia Environmental Project [Member]	Mar. 31, 2013 MGE [Member] Columbia Environmental Project [Member]	Mar. 31, 2014 MGE [Member] Columbia Environmental Project [Member] PSCW [Member]	Dec. 31, 2013 MGE [Member] Columbia Environmental Project [Member] PSCW [Member]	Mar. 31, 2014 Columbia Units [Member] WPL [Member]	Mar. 31, 2014 Columbia Units [Member] WPSC [Member]	Mar. 31, 2014 Columbia Units [Member] MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest										46.20%	31.80%	22.00%
Jointly owned utility plant, total expected capital expenditures						$ 135,000,000
Total incurred costs to date	147,449,000	141,415,000	147,449,000		141,415,000	124,300,000
Jointly owned utility plant, total expected capital expenditures, remainder of current year						10,700,000
Contractual commitments						10,700,000
AFUDC - equity funds			$ 1,950,000	$ 596,000		$ 1,900,000	$ 500,000
Authorized AFUDC Rate								100.00%	50.00%
Authorized MGE rate of return									50.00%